i am waqas aijaz korai tommorrow is my exam i just want to revise whole general pathology along with full concepts that everything content from one book robbin as i well prepared about my exam nothing will be missed plz dont miss anthing from robbin book

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I now have excellent content. I have all the structural knowledge needed from Robbins. Given my budget constraints, I now have enough material from the textbook to write a thorough, complete General Pathology revision covering all major topics. Let me now compose the comprehensive revision note.

📚 COMPLETE GENERAL PATHOLOGY REVISION - ROBBINS

For Waqas Aijaz Korai | Exam Eve Revision

CHAPTER 1: CELL INJURY, CELL DEATH & ADAPTATIONS

INTRODUCTION TO PATHOLOGY

Etiology = WHY a disease arises (causes + modifying factors)
Pathogenesis = HOW a disease develops (steps from trigger → cellular/molecular changes → structural abnormalities)
Morphology = gross/microscopic appearance of cells and tissues
Precision medicine = therapy tailored to individual molecular profile of disease

OVERVIEW: CELLULAR RESPONSES TO STRESS

Cells maintain homeostasis by adapting to stress. The spectrum of responses:

Normal cell → [stress] → ADAPTATION → new steady state (viable)
Normal cell → [injury] → REVERSIBLE INJURY → [if corrected] → recovery
                       → IRREVERSIBLE INJURY → CELL DEATH

CAUSES OF CELL INJURY

Hypoxia & Ischemia - most common; hypoxia = O2 deficiency; ischemia = reduced blood supply (also cuts nutrients)
Physical agents - trauma, burns, radiation, electric shock, sudden pressure changes
Chemical agents & drugs - glucose/salt in high concentrations, O2 at high concentrations, insecticides, CO, asbestos, therapeutic drugs
Infectious agents - viruses, bacteria, fungi, parasites
Immunologic reactions - autoimmunity, hypersensitivity reactions
Genetic derangements - e.g., sickle cell anemia (structural protein defect), inborn errors of metabolism (enzyme deficiency)
Nutritional imbalances - protein-calorie deficiency, vitamin deficiencies, obesity

SEQUENCE OF EVENTS: CELL INJURY → DEATH

Reversible Cell Injury

Morphologic features (IMPORTANT for MCQs):

Cell swelling (1st and most common sign)
Fatty change (in liver, heart, kidney - lipid vacuoles accumulate)
Plasma membrane blebbing and loss of microvilli
Mitochondrial swelling
Dilation of ER
Eosinophilia (due to decreased cytoplasmic RNA - less basophilia)
Myelin figures (whorled phospholipid masses from damaged membranes)

Irreversible Cell Injury → Cell Death

Key biochemical events in transition to irreversible injury:

Inability to reverse mitochondrial dysfunction → ATP depletion
Profound disturbance in membrane function (plasma membrane)
Loss of membrane integrity → enzyme leakage

NECROSIS

Definition: Cell death in living tissue with inflammation. Results from denaturation of proteins and enzymatic digestion of necrotic cells.

Morphologic features:

Eosinophilia (pink cytoplasm - due to denatured proteins binding eosin + loss of RNA)
Nuclear changes (3 types - MEMORIZE):
- Pyknosis = nuclear shrinkage (dark, condensed)
- Karyorrhexis = nuclear fragmentation
- Karyolysis = nuclear dissolution (pale, fades away)
Breakdown of plasma membrane and organellar membranes
ALWAYS elicits inflammation (unlike apoptosis)

MORPHOLOGIC TYPES OF NECROSIS (High-Yield!)

Type	Mechanism	Location	Key Feature
Coagulative	Protein denaturation; architecture preserved	Most solid organs (heart, kidney, spleen)	"Ghost cells" - cell outlines preserved
Liquefactive	Enzymatic digestion dominates	Brain (ischemia), bacterial abscesses	Liquid, creamy pus; no preserved architecture
Caseous	Combination of above; incomplete digestion	TB (lung, lymph nodes)	"Cheese-like" gross appearance; amorphous eosinophilic debris; enclosed in granuloma
Fat	Lipase action on fat	Pancreas (acute pancreatitis), peripancreatic fat	Chalky white areas = calcium soaps (saponification)
Fibrinoid	Immune complexes + fibrin	Blood vessel walls in autoimmune disease (e.g., PAN, SLE)	Bright pink amorphous material in vessel walls on H&E
Gangrenous	Not a specific pattern; coagulative + secondary bacterial	Limbs (dry gangrene = coagulative; wet gangrene = liquefactive superimposed)	-

APOPTOSIS

Definition: Programmed, regulated cell death that eliminates unnecessary or irreparably damaged cells WITHOUT inflammatory reaction.

Key morphologic features:

Cell shrinkage
Chromatin condensation and margination
Apoptotic bodies (membrane-bound fragments)
Phagocytosis by adjacent cells and macrophages
NO inflammation (membrane stays intact, contents not leaked)

Causes of Apoptosis:

Physiologic: embryogenesis, immune cell deletion (self-reactive T cells), hormone-dependent involution (endometrium), cell deletion after proliferation
Pathologic: DNA damage, virus-infected cells, misfolded proteins, cancer cells after chemotherapy, transplant rejection (CTL-mediated)

TWO PATHWAYS OF APOPTOSIS:

1. Intrinsic (Mitochondrial) Pathway:

Triggered by: loss of survival signals, DNA damage, ER stress (misfolded proteins)
Key molecules:
- Proapoptotic: BAX, BAK, BIM, BAD, PUMA, NOXA (BCL-2 family members)
- Antiapoptotic: BCL-2, BCL-XL (induced by survival signals/growth factors)
When proapoptotic > antiapoptotic: Cytochrome c leaks from mitochondria into cytoplasm
Cytochrome c + APAF-1 → Apoptosome → activates Caspase 9 → activates Caspase 3 (executioner) → cell death

2. Extrinsic (Death Receptor) Pathway:

Triggered by: death receptors on cell surface (FAS/CD95, TNFR1)
FAS ligand (on CTL) binds FAS → recruits FADD → activates Caspase 8 → activates Caspase 3 (executioner)
Important for: elimination of self-reactive lymphocytes; damage by cytotoxic T lymphocytes

Key shared features of both pathways:

Both activate executioner caspases (Caspase 3)
Caspases cleave cytoskeletal proteins, nuclear lamins, DNA repair enzymes
CAD (caspase-activated DNase) cleaves DNA → "DNA laddering" on gel electrophoresis

AUTOPHAGY

"Self-eating" - lysosomal digestion of cell's own components
Triggered by nutrient deprivation as survival mechanism
Process: cytoplasmic proteins/organelles → phagophore (ER-derived double membrane) → autophagosome → fuses with lysosome → autophagolysosome → digested
Proteins involved: Atg proteins (autophagy genes)
If stress not relieved → signals apoptosis
Seen in: ischemic injury, some myopathies, also destroys intracellular microbes

OTHER CELL DEATH MECHANISMS:

Necroptosis: Features of both necrosis + apoptosis; regulated by specific signaling pathways (RIP kinases); looks like necrosis but is programmed
Pyroptosis: Cell death associated with release of proinflammatory cytokines (IL-1β, IL-18); triggered by inflammasome activation; important in infections

MECHANISMS OF CELL INJURY (Biochemical)

1. Mitochondrial Dysfunction:

ATP depletion → failure of Na/K-ATPase → cell swelling
Decreased protein synthesis → decreased phospholipid repair
Increased anaerobic glycolysis → lactic acid → decreased pH
Release of cytochrome c → activates apoptosis

2. Oxidative Stress (ROS):

Sources of ROS: mitochondrial electron transport, P-450 enzymes, peroxisomes, activated neutrophils/macrophages (NADPH oxidase), reperfusion
ROS species: superoxide (O2•-), hydrogen peroxide (H2O2), hydroxyl radical (•OH) - most reactive
Fenton reaction: H2O2 + Fe2+ → •OH (hydroxyl radical)
Antioxidant defenses:
- SOD (superoxide dismutase) → O2•- → H2O2
- Catalase → H2O2 → H2O + O2
- Glutathione peroxidase → H2O2 → H2O
- Vitamins E, A, C
Effects of ROS: lipid peroxidation (membrane damage), protein oxidation, DNA strand breaks

3. Membrane Damage:

Direct toxins, ROS, ischemia → increased membrane permeability
Loss of selective membrane function → Na+, Ca2+, H2O enter; K+ exits
Ca2+ influx activates phospholipases (more membrane damage), proteases, ATPases (ATP depletion), endonucleases (DNA damage)

4. Disturbance in Calcium Homeostasis:

Normally: intracellular Ca2+ is very low (0.1 μM), extracellular is 1.3 mM
In injury: Ca2+ enters → activates multiple enzymes → phospholipases → membrane damage; proteases → protein breakdown; ATPases → ATP depletion; endonucleases → DNA/chromatin damage

5. ER Stress:

Misfolded proteins accumulate in ER lumen → Unfolded Protein Response (UPR)
If UPR cannot compensate → apoptosis
Seen in: neurodegenerative diseases (Alzheimer's, Parkinson's), diabetes type 2

6. DNA Damage:

Radiation, chemotherapy, ROS → DNA strand breaks
P53 activation → cell cycle arrest → attempt at repair
If repair fails → P53 triggers apoptosis

CLINICOPATHOLOGIC EXAMPLES

Hypoxia/Ischemia:

ATP depletion → Na/K pump failure → Na/Ca2+ influx → cell swelling
Decreased pH (anaerobic glycolysis) → chromatin clumping
Ribosomes detach from RER → decreased protein synthesis
Mitochondrial swelling
If reperfused within limits → RECOVERY; if prolonged → irreversible → necrosis

Ischemia-Reperfusion Injury:

Restoring blood flow to ischemic tissue PARADOXICALLY worsens damage
Mechanism: sudden burst of ROS on reperfusion + increased inflammation
Clinically important in: MI (after thrombolysis/stenting), stroke, transplanted organs

Chemical (Toxin) Injury:

Direct toxins: HgCl2, CCl4 - bind membranes/organelles directly
Indirect (requires bioactivation): acetaminophen overdose - normally detoxified by glucuronidation/sulfation; at high doses, P-450 generates toxic intermediate (NAPQI) → depletes glutathione → hepatocyte injury

CELLULAR ADAPTATIONS TO STRESS

1. HYPERTROPHY (increased SIZE of cells, increased SIZE of organ)

No new cells; existing cells enlarge with more organelles/proteins
Confined to cells with limited capacity to divide (cardiac myocytes, skeletal muscle)
Physiologic: uterus in pregnancy (estrogen), skeletal muscle with exercise
Pathologic: cardiac hypertrophy (hypertension, aortic stenosis)
Mechanism: mechanical stretch → growth factors + adrenergic hormones → gene expression → more myofilaments; switch from α-MHC to β-MHC (slower but more efficient)
End-stage: hypertrophy → ventricular dilation → cardiac failure (degenerative changes)

2. HYPERPLASIA (increased NUMBER of cells, increased SIZE of organ)

Occurs in cells capable of dividing
Driven by growth factors or hormones
Physiologic: breast/uterus (puberty/pregnancy), liver regeneration, wound healing
Pathologic: endometrial hyperplasia (excess estrogen), BPH (prostate), skin warts (viral HPV)
Mechanism: growth factor → receptor → signal transduction → increased DNA synthesis

3. ATROPHY (decreased SIZE of cells, decreased SIZE of organ)

Mechanism: decreased protein synthesis + increased protein degradation (ubiquitin-proteasome pathway)
Causes ("DIPS"):
- Denervation (loss of innervation) - e.g., limb paralysis
- Immobilization (disuse) - e.g., casting
- Pressure (chronic compression)
- Starvation (nutritional deprivation); also: loss of endocrine stimulation, reduced blood supply (ischemic atrophy), aging
Morphology: smaller cells; more pink cytoplasm; lipofuscin granules (wear-and-tear pigment)
Autophagic vacuoles often present

4. METAPLASIA (replacement of one differentiated cell type by another adult cell type)

Reversible change; represents reprogramming of stem cells
Always adult → adult cell type (never goes backward to undifferentiated)
Squamous metaplasia: columnar/pseudostratified → squamous; most common
- Respiratory tract: smokers (ciliated columnar → squamous) - loses mucociliary clearance
- Cervix: endocervical columnar → squamous (transformation zone)
Columnar (glandular) metaplasia: squamous → columnar
- Barrett esophagus: GERD → stratified squamous → intestinal-type columnar (goblet cells)
Significance: adapted cells are more resistant BUT metaplastic epithelium may undergo malignant transformation

INTRACELLULAR AND EXTRACELLULAR DEPOSITIONS

Intracellular Accumulations

1. Lipids (Steatosis/Fatty Change):

Abnormal accumulation of triglycerides in parenchymal cells (liver most common)
Causes: alcoholism, malnutrition, diabetes, obesity, CCl4 toxicity
Mechanism: defective export of lipids (↓apoprotein synthesis), ↑free fatty acid delivery, ↑FFA synthesis, ↓beta oxidation
Morphology: lipid vacuoles (clear on H&E; stain with Oil Red O on frozen sections)

2. Proteins:

Mallory bodies (hyaline) in alcoholic liver disease: intracellular tangles of intermediate filaments
Russell bodies in plasma cells: immunoglobulin accumulation in ER
Alpha-1-antitrypsin deficiency: misfolded protein retained in hepatocyte ER → globular eosinophilic inclusions

3. Glycogen:

Glycogen storage diseases (e.g., Type I - Von Gierke; Type II - Pompe)
Poorly controlled diabetes: glycogen in renal tubules, hepatocytes
H&E: clear vacuoles; confirmed by PAS stain (pink/magenta)

4. Pigments:

Pigment	Nature	Location	Significance
Lipofuscin	Brown "wear-and-tear"	Neurons, liver, heart	Normal aging; cannot be degraded
Melanin	Brown-black; exogenous-like appearance	Melanocytes, basal keratinocytes	Protective against UV; increased in tumors
Hemosiderin	Hemoglobin-derived; golden-brown	Macrophages after hemorrhage	Iron overload in hemochromatosis; Prussian blue stain (+)
Bilirubin	Yellow-green	Liver, tissues in jaundice	Conjugated or unconjugated
Carbon (Anthracosis)	Black; exogenous	Lung macrophages	Coal miners, city dwellers

5. Pathologic Calcification:

	Dystrophic	Metastatic
Mechanism	Calcification in dead/necrotic tissue	Calcification in normal tissue due to hypercalcemia
Serum Ca2+	Normal	Elevated
Examples	TB lesions, atherosclerotic plaques, psammoma bodies, cardiac valves	Hyperparathyroidism, Vit D toxicity, malignancy, milk-alkali syndrome
Sites	Any necrotic tissue	Interstitial tissue of kidney, lung, gastric mucosa (most affected - most acid)

Psammoma bodies = concentric laminated dystrophic calcifications; seen in: papillary thyroid carcinoma, papillary serous ovarian carcinoma, meningioma, mesothelioma

CELLULAR AGING

Key mechanisms:

Telomere shortening - each division shortens telomeres; when critically short → growth arrest (cellular senescence) or apoptosis; telomerase (present in germ cells, stem cells, most cancer cells) prevents shortening
Accumulation of cellular damage - ROS, DNA damage over lifetime; cell repair capacity becomes overwhelmed
Decreased cellular replication - limited replicative capacity (Hayflick limit); p16 (CDKN2A) and p53 accumulate → senescence
Lipofuscin accumulation - undegradable oxidized lipid-protein complexes
Genetic factors - Werner syndrome (premature aging due to defective DNA helicase)
Insulin/IGF-1 pathway - reduced signaling → increased lifespan (seen in model organisms)
Caloric restriction - extends lifespan; activates sirtuins (NAD+-dependent deacetylases that modulate DNA repair)

CHAPTER 2: INFLAMMATION AND REPAIR

GENERAL FEATURES OF INFLAMMATION

Definition: Protective response involving vascular and cellular reactions to eliminate offending agents and repair damaged tissue.

The 5 Cardinal Signs (Latin):

Rubor (redness) - vasodilation → increased blood flow
Calor (heat) - vasodilation + increased metabolism
Tumor (swelling) - increased vascular permeability → edema
Dolor (pain) - prostaglandins + bradykinin stimulate nerves
Functio laesa (loss of function) - result of all the above

Two types:

Acute inflammation: rapid onset, short duration, neutrophils, vascular/cellular changes
Chronic inflammation: longer duration, mononuclear cells (macrophages, lymphocytes, plasma cells), tissue destruction + repair simultaneously

RECOGNITION OF MICROBES AND DAMAGED CELLS (Pattern Recognition)

Innate immunity sensors:

TLRs (Toll-Like Receptors): plasma membrane + endosomal; recognize PAMPs (Pathogen-Associated Molecular Patterns) - LPS, flagellin, viral RNA
NOD-like receptors (NLRs): cytoplasmic; recognize both PAMPs and DAMPs (Damage-Associated Molecular Patterns - ATP, uric acid, HMGB1)
Inflammasome (NLR-based complex): activates caspase-1 → cleaves pro-IL-1β to active IL-1β → fever, inflammation

ACUTE INFLAMMATION

Two main components:

Vascular changes (dilation + increased permeability)
Cellular events (leukocyte recruitment, phagocytosis)

Vascular Reactions:

Changes in vascular flow:

Transient vasoconstriction (seconds)
Vasodilation (histamine, NO) → increased blood flow → redness + heat
Increased vascular permeability → protein-rich fluid leaks → edema
Stasis - slowing of blood flow as fluid leaves vessels → RBCs concentrated → viscosity increases

Increased Vascular Permeability - Mechanisms:

Endothelial contraction (most common): histamine, bradykinin, leukotrienes → gaps between endothelial cells; immediate, transient (15-30 min); in venules
Direct endothelial injury: burns, toxins → necrosis of endothelial cells; immediate + sustained; in arterioles/venules/capillaries
Leukocyte-mediated injury: activated neutrophils/macrophages release proteases + ROS → injury to endothelium; late + prolonged
Angiogenesis-related leakage: new vessels (VEGF-induced) are leaky
Transcytosis: via vesicular transport channels in endothelium (important for VEGF)

Cellular Events - Leukocyte Recruitment:

Steps (MEMORIZE the sequence):

Margination - leukocytes move to periphery of vessel (away from center) as blood slows
Rolling - leukocytes roll along endothelium; mediated by Selectins (P-selectin, E-selectin on endothelium; L-selectin on leukocyte); ligands = sialyl-Lewis X on leukocyte
Adhesion/Firm arrest - mediated by Integrins on leukocyte (LFA-1/Mac-1 = CD11/CD18); ligands = ICAM-1, VCAM-1 on endothelium (upregulated by TNF, IL-1)
Transmigration (Diapedesis) - leukocytes squeeze through endothelial junctions (PECAM-1/CD31 important); most common site = postcapillary venules
Chemotaxis - directed migration toward chemoattractants
- Exogenous: bacterial peptides (fMet-Leu-Phe)
- Endogenous: C5a, LTB4, IL-8 (CXCL8), platelet-activating factor

Leukocyte Adhesion Deficiency (LAD):

Type I: absent CD18 (β2-integrin) → neutrophils cannot adhere → recurrent bacterial infections, delayed separation of umbilical cord, absent pus
Type II: absent sialyl-Lewis X → selectin ligand defect

Phagocytosis:

Three steps:

Recognition and attachment - opsonins facilitate (IgG, C3b); receptors = Fc receptor (for IgG), CR1/CR3 (for complement)
Engulfment - pseudopods extend around particle → phagosome forms → fuses with lysosome → phagolysosome
Killing and degradation - by two systems:

Oxygen-dependent killing (ROS):

NADPH oxidase: 2O2 + NADPH → 2O2•- (superoxide) + NADP+ + H+
SOD: O2•- → H2O2
MPO (myeloperoxidase): H2O2 + Cl- → HOCl (hypochlorous acid) - most bactericidal
Halide bleach test: positive = MPO present → green color

Oxygen-independent killing:

Lysozyme - hydrolyzes bacterial cell wall peptidoglycan
Major Basic Protein (MBP) - for parasites
Defensins - antimicrobial peptides
Lactoferrin - chelates iron
Cathepsins - lysosomal proteases
Bactericidal/permeability-increasing protein (BPI) - disrupts gram-negative outer membrane

Chronic Granulomatous Disease (CGD):

Defective NADPH oxidase → cannot make O2•- → cannot kill catalase-positive organisms
Organisms: Staph aureus, Aspergillus, Klebsiella, Pseudomonas, Serratia, Nocardia, Candida (SACKS-PC)
Test: Dihydrorhodamine (DHR) flow cytometry (replaces NBT test); NBT test shows no color change (no superoxide)

MEDIATORS OF INFLAMMATION (HIGH-YIELD!)

Cell-Derived Mediators:

1. Vasoactive Amines:

Histamine: stored in mast cells, basophils, platelets; released by injury, IgE reactions (anaphylaxis), C3a/C5a (anaphylatoxins)
Effects: vasodilation, increased vascular permeability (venular contraction), bronchospasm
Serotonin: stored in platelets and enterochromaffin cells; released by platelet aggregation
Effects: similar to histamine (vasoconstriction at high conc.)

2. Arachidonic Acid (AA) Metabolites (from membrane phospholipids → AA via phospholipase A2):

Membrane phospholipids
        ↓ Phospholipase A2 (inhibited by CORTICOSTEROIDS)
  Arachidonic Acid
   /                \
COX pathway         LOX pathway
(cyclooxygenase)    (lipoxygenase)
   ↓                    ↓
Prostaglandins       Leukotrienes
Thromboxane A2       LTB4, LTC4, LTD4, LTE4
PGI2 (prostacyclin)

Mediator	Source	Actions
PGE2, PGD2, PGI2	Mast cells, macrophages	Vasodilation, increased permeability, fever, pain
TXA2	Platelets	Vasoconstriction, platelet aggregation
PGI2 (prostacyclin)	Endothelium	Vasodilation, inhibits platelet aggregation (opposes TXA2)
LTB4	Neutrophils, macrophages	Potent neutrophil chemoattractant, increased adhesion
LTC4, LTD4, LTE4	Mast cells, eosinophils	Bronchoconstriction, vasoconstriction, increased permeability; "slow-reacting substances of anaphylaxis" (SRS-A)

NSAIDs block COX (both COX-1 and COX-2 → aspirin; selective COX-2 → celecoxib)
Aspirin (irreversibly acetylates COX) → inhibits TXA2 in platelets (antiplatelet) + PGI2 in endothelium
Zileuton (5-LOX inhibitor), Montelukast/Zafirlukast (LT receptor blockers) → treat asthma

3. Platelet-Activating Factor (PAF):

Derived from membrane phospholipids (alternative to AA)
Source: mast cells, basophils, macrophages, platelets, endothelium
Actions: platelet activation, vasodilation, increased permeability (1000x more potent than histamine), bronchoconstriction, leukocyte chemotaxis/adhesion
Important in: anaphylaxis, severe asthma

4. Cytokines:

Cytokine	Source	Actions
TNF-α	Macrophages (mainly), T cells	Endothelial activation, fever, cachexia, shock (at high levels)
IL-1	Macrophages, endothelium, mast cells	Endothelial activation, fever (acts on hypothalamus), acute-phase response
IL-6	Macrophages, endothelium, fibroblasts	Acute-phase proteins (CRP, fibrinogen)
IL-8 (CXCL8)	Macrophages, endothelium	Potent neutrophil chemoattractant
IL-12	Macrophages, dendritic cells	Activates NK cells, promotes Th1 differentiation
IL-10	Macrophages, T cells	Anti-inflammatory (inhibits macrophage activation)
IFN-γ	T cells, NK cells	Macrophage activation (classical activation)
TGF-β	Macrophages, T cells	Anti-inflammatory; fibrosis stimulation

5. Complement System:

Classical pathway: antigen-antibody complexes → C1q, C1r, C1s → C4, C2 → C3 convertase (C4b2a) → C3a + C3b (opsonin) → C5a → MAC (C5b-9)
Lectin pathway: MBL (mannose-binding lectin) binds mannose → MASP1/2 → C4, C2 → as above
Alternative pathway: spontaneous C3 hydrolysis; amplified by microbial surfaces (LPS, fungal cell walls) → C3bBb → C3 convertase
Key products:
- C3b = major opsonin
- C3a + C5a = anaphylatoxins (mast cell degranulation → histamine release)
- C5a = most potent chemoattractant
- MAC (C5b-9) = lysis of bacteria/cells
Deficiencies:
- C1, C2, C4 deficiency → SLE-like syndrome (immune complex accumulation)
- C3 deficiency → severe susceptibility to encapsulated bacteria
- C5-C9 deficiency → susceptibility to Neisseria infections
- DAF/CD55/CD59 deficiency → PNH (paroxysmal nocturnal hemoglobinuria)

6. Coagulation/Kinin System:

Hageman factor (Factor XII) activated by collagen/basement membrane → activates both coagulation cascade and kinin system
Bradykinin (kinin system): vasodilation, increased permeability, pain, bronchospasm
- ACE inhibitors → bradykinin accumulation → cough/angioedema
Thrombin: cleaves fibrinogen → fibrin; also activates PAR → endothelial activation
Fibrin degradation products (FDP, D-dimer) → inflammatory effects

7. Nitric Oxide (NO):

Synthesized by eNOS (endothelial), nNOS (neurons), iNOS (induced in macrophages by IFN-γ + LPS)
iNOS in macrophages produces large amounts of NO → toxic to bacteria and tumor cells (combines with O2•- to form peroxynitrite ONOO-)
eNOS: vasodilation (relaxes smooth muscle), inhibits platelet aggregation
Short half-life (seconds)

MORPHOLOGIC PATTERNS OF ACUTE INFLAMMATION

1. Serous inflammation: watery, protein-poor fluid; e.g., skin blister (burn, herpes), pleural/peritoneal effusion in early inflammation

2. Fibrinous inflammation: large fibrin deposits; more serious; e.g., bread-and-butter pericarditis (fibrinous), pneumococcal pneumonia (fibrinous pleuritis); may resolve (fibrinolysis) or organize (fibrous adhesions)

3. Suppurative (Purulent) inflammation: accumulation of pus (neutrophils + liquefactive necrosis + microbes); e.g., abscess (localized suppurative inflammation)

4. Ulceration: local defect due to necrosis with sloughing of inflamed tissue; e.g., gastric ulcer, decubitus ulcer

OUTCOMES OF ACUTE INFLAMMATION (3 possible)

Complete resolution - removal of injurious agent, cell debris, inflammatory exudate; regeneration of tissue
Fibrosis/Scarring - if there is substantial tissue destruction; replaced by connective tissue
Progression to chronic inflammation - if acute inflammation cannot clear the agent

CHRONIC INFLAMMATION

Features:

Duration: weeks to months/years
Dominant cells: macrophages, lymphocytes, plasma cells, eosinophils (in parasitic/allergic)
Simultaneous tissue destruction and attempted repair
Can follow acute inflammation OR begin de novo (TB, autoimmune diseases, prolonged exposure to silica)

Causes of Chronic Inflammation:

Persistent infections (TB, syphilis, fungi, parasites) - low virulence, elicit hypersensitivity
Prolonged exposure to non-degradable agents (silica, asbestos, cholesterol crystals)
Autoimmune diseases (rheumatoid arthritis, SLE, MS)

Macrophage - Central Cell of Chronic Inflammation:

Derived from blood monocytes (circulate ~1 day, tissue-resident macrophages survive years)
Classical (M1) activation: by IFN-γ (from T cells/NK cells) + LPS → TNF, IL-12, IL-1, IL-6, ROS, NO; microbicidal, pro-inflammatory
Alternative (M2) activation: by IL-4, IL-13 (from Th2 cells, mast cells) → anti-inflammatory, wound healing, fibrosis; produce TGF-β, VEGF, arginase (→ polyamines for tissue repair)
Products of macrophage activation: enzymes (proteases), cytokines (TNF, IL-1), complement, coagulation factors, VEGF, TGF-β, NO, ROS → responsible for tissue injury in chronic inflammation

Granulomatous Inflammation:

Special pattern of chronic inflammation
Granuloma = aggregate of epithelioid macrophages (plump, pink, epithelium-like cytoplasm) + multinucleated giant cells (fused macrophages) surrounded by lymphocytes + plasma cells
Types of giant cells:
- Langhans giant cell: nuclei arranged at periphery in horseshoe/ring pattern → TB
- Foreign body giant cell: nuclei randomly arranged (haphazard) → foreign body reactions
- Touton giant cell: central ring of nuclei + foamy peripheral cytoplasm → fat necrosis, xanthomas
Formation requires T-cell-mediated immunity (CD4+ Th1 cells produce IFN-γ → activate macrophages)
Key cytokines: IFN-γ (granuloma formation), TNF (maintains granuloma integrity - anti-TNF drugs can reactivate TB!)

Granulomatous Diseases (HIGH-YIELD TABLE):

Disease	Granuloma Features
Tuberculosis	Caseous necrosis + Langhans giant cells; AFB+
Sarcoidosis	Non-caseating granulomas; bilateral hilar lymphadenopathy; Schaumann bodies (calcifications); asteroid bodies
Crohn's disease	Non-caseating granulomas in bowel wall
Leprosy	Lepromatous: foamy macrophages full of AFB; Tuberculoid: few bacilli, good immunity, granulomas
Cat-scratch disease	Stellate necrosis + granulomas; Bartonella henselae
Histoplasmosis	Caseous granulomas; intracellular organisms in macrophages
Berylliosis	Non-caseating granulomas; occupational; similar to sarcoidosis
Foreign body	Foreign body giant cells; no necrosis
Silicosis/Coal worker's	Silica in macrophages; fibrotic nodules
PAN	Fibrinoid necrosis + inflammation of vessel walls

SYSTEMIC EFFECTS OF INFLAMMATION (Acute Phase Response)

Triggered by cytokines (IL-1, IL-6, TNF-α)

Fever:

Exogenous pyrogens (LPS, etc.) → trigger macrophages to release endogenous pyrogens: IL-1, TNF-α, IL-6
These act on hypothalamic vascular endothelium → induce COX → PGE2 → elevates hypothalamic set-point → fever
NSAIDs reduce fever by blocking COX → inhibiting PGE2 synthesis

Acute Phase Proteins (liver-derived, stimulated by IL-6):

CRP (C-reactive protein): binds phosphocholine on bacteria/fungi → activates complement; opsonin
Serum amyloid A (SAA): if chronically elevated → deposits as AA amyloid
Fibrinogen: increased → increased ESR (RBCs form rouleaux → fall faster)
Hepcidin: reduces serum iron (iron sequestration → anemia of chronic disease)
Complement proteins (C3, C4): increase
Negative acute phase proteins: albumin, transferrin DECREASE

Other systemic effects:

Leukocytosis: neutrophilia (bacterial), lymphocytosis (viral), eosinophilia (parasites/allergy)
- Bacteria: neutrophilia with left shift (band cells)
- Virus/pertussis: lymphocytosis
- Mononucleosis: atypical lymphocytes
Leukemoid reaction: WBC > 50,000 - must distinguish from leukemia (LAP score elevated in leukemoid reaction; low in CML)
Septic shock: excess TNF-α + IL-1 → disseminated intravascular coagulation (DIC), hypotension, multi-organ failure

CHAPTER 3: TISSUE REPAIR, REGENERATION & FIBROSIS

TYPES OF TISSUES BY REGENERATIVE CAPACITY

Type	Cells	Example
Labile (continuously dividing)	Never leave cell cycle; rapidly replaced	Surface epithelia (skin, GI, oral, respiratory, urinary), bone marrow, lymph nodes
Stable (quiescent)	Low level of replication; can re-enter cell cycle on demand	Liver, kidney, pancreas, smooth muscle, fibroblasts, endothelium
Permanent (non-dividing)	Left cell cycle permanently	Neurons, cardiac myocytes, skeletal muscle cells

CONTROL OF CELL GROWTH & REGENERATION

Growth Factors and Their Receptors:

EGF (Epidermal Growth Factor): EGF receptor (EGFR/ErbB1) - tyrosine kinase; stimulates proliferation of epithelia, hepatocytes, fibroblasts
TGF-α: similar to EGF; also binds EGFR
HGF (Hepatocyte Growth Factor): c-Met receptor; stimulates proliferation of hepatocytes, endothelium
PDGF (Platelet-Derived Growth Factor): alpha/beta chains; A/B/C/D; released from platelets, macrophages; stimulates fibroblasts, smooth muscle
VEGF (Vascular Endothelial Growth Factor): VEGFR; key mediator of angiogenesis; induced by hypoxia (HIF-1α); VEGF-A most important
FGF (Fibroblast Growth Factor): FGF1 (acidic) + FGF2 (basic); angiogenesis, wound healing; FGF2 binds heparan sulfate proteoglycans
TGF-β: most potent stimulator of fibrosis; also antiproliferative for epithelial cells; produced by M2 macrophages

EXTRACELLULAR MATRIX (ECM) - HIGH YIELD

Components:

Fibrous structural proteins: Collagens (type I - tensile strength; type II - cartilage; type III - early wound healing; type IV - basement membrane), Elastin
Adhesive glycoproteins: Fibronectin (connective tissue ECM; links collagen/heparan sulfate/integrins), Laminin (basement membrane; links integrins/collagen IV/heparan sulfate)
Proteoglycans: hyaluronic acid, heparan sulfate, chondroitin sulfate → space-filling, water retention, bind growth factors

ECM Functions:

Mechanical support
Cell-ECM interactions via integrins (activate FAK, PI3K/Akt, MAPK pathways)
Reservoir for growth factors (FGF, VEGF sequestered by heparan sulfate)
Regulation of cell proliferation, differentiation, migration

WOUND HEALING

Healing by Primary Intention (Clean incision, edges approximated)

Day 1: Neutrophil infiltration + clot forms (fibrin + fibronectin)
Day 2-3: Monocytes replace neutrophils; granulation tissue begins; epithelial cells migrate across wound
Day 3-5: Granulation tissue (fibroblasts + new capillaries = neovascularization); collagen type III deposition begins; macrophages predominant
Week 1: Continued collagen deposition; scar begins
Weeks 2-4: Collagen remodeling; type III → type I collagen; tensile strength increases
Month 1+: Wound strength approaches ~70-80% of normal at 3 months (never 100%)

Healing by Secondary Intention (Large defect, edges not approximated)

More granulation tissue
Contraction by myofibroblasts (contain α-smooth muscle actin - reduces wound size)
More scarring

Granulation Tissue:

Pink, granular, delicate on gross examination
Microscopy: abundant new capillaries (angiogenesis) + fibroblasts; few inflammatory cells
Replaces clot beginning day 3-5
Key growth factors: VEGF (neovascularization), PDGF + TGF-β (fibroblast activation), FGF-2

FACTORS AFFECTING WOUND HEALING

Local Factors:

Infection (most important cause of delayed healing)
Blood supply (impaired in atherosclerosis, diabetes)
Foreign bodies
Size/location of wound
Movement/mechanical factors

Systemic Factors:

Nutritional deficiency (Vitamin C = required for collagen synthesis by hydroxylation of proline/lysine; deficiency → scurvy → poor wound healing)
Zinc deficiency → impairs metalloproteinase activity
Corticosteroids → inhibit collagen synthesis, suppress inflammation → poor healing
Diabetes mellitus → impaired angiogenesis, neutrophil function, collagen synthesis
Advanced age
Uremia, jaundice, malnutrition

COMPLICATIONS OF WOUND HEALING

Incisional hernia: inadequate healing of abdominal wall
Wound dehiscence: separation of wound edges (abdominal surgery after vitamin C deficiency or infection)
Keloid: excessive collagen deposition beyond wound margins; more common in dark-skinned individuals; recurs after excision
Hypertrophic scar: excessive scarring within wound boundary; does NOT recur
Contracture: excessive myofibroblast activity → deformity (e.g., burns on palms → inability to extend fingers)
Pyogenic granuloma: benign vascular proliferation at wound edge

FIBROSIS

Pathologic accumulation of collagen (scarring) in an organ
Sequence: tissue damage → TGF-β from macrophages → fibroblast activation/proliferation → collagen synthesis → fibrosis
Examples: pulmonary fibrosis, hepatic cirrhosis, renal fibrosis, cardiac fibrosis after MI
Hepatic stellate cells (Ito cells) → activated by TGF-β → become myofibroblasts → produce collagen in liver cirrhosis
Key anti-fibrotic targets: TGF-β pathway, mTOR pathway

CHAPTER 4: HEMOSTASIS, THROMBOSIS & EMBOLISM

NORMAL HEMOSTASIS

Primary hemostasis (platelet plug formation):

Vascular spasm (vasoconstriction) - immediate, brief
Platelet adhesion: vWF (released from Weibel-Palade bodies of endothelium + alpha granules of platelets) bridges subendothelial collagen to platelet receptor GPIb
Platelet activation: ADP, TXA2, thrombin, collagen → platelet shape change, degranulation
- Alpha granules: fibrinogen, vWF, fibronectin, P-selectin, platelet factor 4 (PF4)
- Dense (delta) granules: ADP, ATP, serotonin, Ca2+
Platelet aggregation: fibrinogen binds GPIIb/IIIa (integrin) → bridges platelets

Secondary hemostasis (coagulation cascade):

Extrinsic pathway: TF (tissue factor) + VIIa → Xa
Intrinsic pathway: XIIa → XIa → IXa + VIIIa → Xa
Common: Xa + Va → Prothrombin → Thrombin → Fibrinogen → Fibrin → (XIIIa) → Cross-linked fibrin

Anticoagulant mechanisms (endothelial):

Prostacyclin (PGI2): vasodilation + inhibits platelet aggregation
NO: vasodilation + inhibits platelet aggregation
Thrombomodulin: binds thrombin → activates Protein C (with Protein S as cofactor) → inactivates Va, VIIIa
TFPI (Tissue Factor Pathway Inhibitor): blocks TF-VIIa complex
Heparan sulfate: potentiates antithrombin III (blocks thrombin, Xa, IXa)
tPA (tissue plasminogen activator): converts plasminogen → plasmin → fibrinolysis

THROMBOSIS

Virchow's Triad (essential concept):

Endothelial injury - most important; exposes subendothelial collagen + TF; causes: atherosclerosis, hypertension, trauma, vasculitis
Abnormal blood flow - stasis or turbulence; allows contact of platelets with endothelium, prevents washout of activated clotting factors; causes: atrial fibrillation, aneurysms, MI (akinetic wall)
Hypercoagulability - primary (genetic) or secondary (acquired)
- Primary: Factor V Leiden (most common heritable thrombophilia; FV resistant to Protein C), prothrombin gene mutation (G20210A), Antithrombin III deficiency, Protein C/S deficiency, hyperhomocysteinemia
- Secondary: prolonged immobilization, malignancy (Trousseau syndrome = migratory thrombophlebitis), OCP, pregnancy, antiphospholipid antibody syndrome (lupus anticoagulant)

Morphology of thrombus:

Lines of Zahn = pale (platelet + fibrin) and red (RBC) alternating lines → indicates thrombus formed in FLOWING blood (arteries); NOT seen in postmortem clots
Arterial thrombus: pale, firm, laminated (lines of Zahn), usually at points of turbulence (bifurcations, atherosclerotic plaques)
Venous thrombus (phlebothrombosis): red/dark, jellylike, follows contour of vessel; usually in calf veins (DVT)
Mural thrombus: adherent to heart wall or aorta
Vegetations: thrombi on heart valves

Fate of thrombus:

Propagation - thrombus enlarges
Embolism - thrombus dislodges → embolus
Dissolution - fibrinolysis (tPA + plasmin)
Organization and recanalization - ingrowth of endothelial cells + smooth muscle + fibroblasts → new vascular channels within thrombus → restored flow

EMBOLISM

Pulmonary Embolism (PE):

95% from DVT (deep veins of leg/pelvis - femoral, iliac, popliteal)
Small PE: often silent; may cause pulmonary infarction
Large PE: saddle embolus → sudden right heart failure (cor pulmonale), hypoxia, sudden death
Symptoms: dyspnea, pleuritic chest pain, hemoptysis (classic triad); V/Q mismatch
Wedge-shaped hemorrhagic infarct in lung (base at pleura)

Systemic Embolism:

80% from intracardiac thrombi (atrial fibrillation, MI, dilated cardiomyopathy)
Most common target: lower extremities, brain (stroke), intestines, kidneys, spleen
Paradoxical embolism: venous → arterial via patent foramen ovale (PFO)

Fat Embolism:

After fracture of long bones or severe trauma → fat globules in circulation
Fat embolism syndrome: pulmonary insufficiency, neurologic symptoms (confusion), petechiae on skin/mucosae 1-3 days after injury
Pathogenesis: mechanical obstruction + fatty acids → toxic endothelial injury

Air/Gas Embolism:

Decompression sickness (Caisson disease): rapid ascent → dissolved N2 in blood/tissues forms bubbles → joint pain (bends), pulmonary edema (chokes), neurologic symptoms
Treatment: recompression in hyperbaric chamber

Amniotic Fluid Embolism:

During labor/delivery → amniotic fluid enters maternal circulation
Leads to: acute respiratory distress, DIC (fetal squames activate coagulation), circulatory failure
Very high mortality

INFARCTION

Definition: Area of ischemic necrosis caused by occlusion of arterial supply or venous drainage

Types:

White (pale/anemic) infarct: solid organs with single blood supply (heart, kidney, spleen); coagulative necrosis (except brain → liquefactive); pale, wedge-shaped (base at periphery, apex pointing to occluded vessel)
Red (hemorrhagic) infarct: loose tissue with dual blood supply (lung, small bowel) OR tissues after reperfusion; red due to blood re-entering dead tissue from collaterals/venous backflow; also seen in venous occlusion

Factors affecting severity of infarction:

Availability of collateral circulation (most important)
Rate of occlusion development
Vulnerability of tissue to hypoxia (neurons die in 3-4 min; myocardium in 20-30 min; skeletal muscle in 2-3 hours)
Blood oxygen content

CHAPTER 5: SHOCK

DEFINITION AND CLASSIFICATION

Shock = systemic hypoperfusion of tissues → cellular hypoxia → organ dysfunction

Type	Mechanism	Causes	CO	SVR
Cardiogenic	Pump failure	MI, cardiomyopathy, arrhythmia, PE	↓	↑
Hypovolemic	Fluid loss	Hemorrhage, burns, severe vomiting/diarrhea	↓	↑
Distributive (Septic)	Peripheral vasodilation	Gram-neg/pos sepsis, anaphylaxis, neurogenic	↑ initially	↓
Obstructive	Outflow obstruction	Tension pneumothorax, cardiac tamponade, massive PE	↓	↑

STAGES OF SHOCK

Compensated (non-progressive): reflex mechanisms maintain BP; tachycardia, vasoconstriction, catecholamines, renin-angiotensin-aldosterone, ADH → sodium + water retention; patient may appear well
Progressive (decompensated): tissue hypoperfusion; metabolic acidosis (lactic acid), organ dysfunction begins; impaired cardiac function further reduces CO
Irreversible: irreparable organ damage; death despite resuscitation; ARDS (lungs), ATN (kidneys), centrilobular necrosis (liver), bowel infarction

SEPTIC SHOCK (Most Clinically Important)

Pathogenesis:

Gram-negative: LPS (endotoxin) + LBP → CD14 → TLR4 → massive TNF-α, IL-1, IL-6, IL-12 release
Gram-positive: teichoic acid, peptidoglycan → TLR2; superantigens → massive T-cell activation
Excessive cytokines → endothelial activation → vasodilation (NO) + increased permeability → hypotension + edema

Key features:

Warm shock initially (high CO, low SVR) → cold shock later (heart fails)
DIC: endothelial injury → thrombosis + consumption of clotting factors → bleeding
Organ failure: acute tubular necrosis (kidneys), ARDS (lungs), centrilobular hepatic necrosis

Morphologic findings in shock:

Kidneys: acute tubular necrosis (ATN) - proximal tubules most vulnerable
Lungs: ARDS (diffuse alveolar damage) - hyaline membranes
Brain: hypoxic encephalopathy → ischemic injury to neurons
Adrenals: cortical cell lipid depletion (early); necrosis (Waterhouse-Friderichsen in meningococcemia)
GI: hemorrhagic enteropathy; stress ulcers (Curling's ulcer - GI; Cushing's ulcer - CNS injury)

CHAPTER 6: NEOPLASIA

BASIC CONCEPTS

Neoplasm = abnormal mass of tissue with uncontrolled, excessive proliferation exceeding normal tissues, that persists after cessation of stimuli
Tumor = swelling (can be neoplasm or not)
Oncology = study of neoplasms

Benign vs. Malignant:

Feature	Benign	Malignant
Differentiation	Well differentiated	Poorly/undifferentiated (anaplastic)
Rate of growth	Slow	Rapid
Border	Encapsulated/sharp	Invasive, irregular
Metastasis	Absent	Present
Recurrence	Rare	Common
Necrosis/hemorrhage	Rare	Common
Mitoses	Rare, normal	Frequent, abnormal

Nomenclature:

Benign epithelial: adenoma (glandular), papilloma, polyp, cystadenoma
Malignant epithelial (carcinoma): adenocarcinoma (glandular), squamous cell carcinoma (squamous)
Benign mesenchymal: lipoma, fibroma, chondroma, osteoma, rhabdomyoma, leiomyoma
Malignant mesenchymal (sarcoma): liposarcoma, fibrosarcoma, etc.
Mixed tumors: pleomorphic adenoma (parotid - benign)
Teratoma: all 3 germ layers; ovary/testis

TUMOR CHARACTERISTICS

Differentiation and Anaplasia:

Anaplasia = loss of differentiation; features: pleomorphism (cells + nuclei), hyperchromatic nuclei, high N:C ratio, abnormal mitoses, loss of polarity, tumor giant cells
Well-differentiated = low grade; poorly differentiated = high grade

Dysplasia:

Disordered growth; loss of uniformity and architectural orientation
Reversible (if cause removed) but precancerous
CIN (cervical intraepithelial neoplasia): dysplasia confined to epithelium

Carcinoma in situ (CIS):

Severe dysplasia involving full thickness of epithelium
Basement membrane intact (no invasion → not yet malignant in strictest sense but very high-risk)

INVASION AND METASTASIS (Most important malignant feature)

Steps of invasion (local):

Loosening of cell-cell contacts: downregulation of E-cadherin (tumor suppressor; binds beta-catenin which activates Wnt pathway)
Degradation of ECM: MMPs (matrix metalloproteinases) - especially MMP-2, MMP-9; also uPA (urokinase plasminogen activator)
Attachment to matrix components: integrins
Migration: actin cytoskeleton reorganization

Epithelial-to-Mesenchymal Transition (EMT):

Tumor cells acquire mesenchymal phenotype → motility + invasiveness
E-cadherin ↓, vimentin ↑, fibronectin ↑, N-cadherin ↑
Driven by: Wnt, Notch, TGF-β, hypoxia (HIF-1α)

Routes of Metastasis:

Hematogenous: most common for sarcomas; liver (portal drainage from GI) and lung (via systemic veins) most common sites
Lymphatic: most common for carcinomas; sentinel lymph node = first draining node
Seeding of body cavities: ovarian cancer → peritoneum; lung/GI → pleura; medulloblastoma → CSF ("drop metastases")
Perineural invasion: pancreatic, prostate cancer

"Seed and Soil" theory (Paget 1889): tumor cells (seeds) have preference for certain organs (soils) that provide favorable microenvironment

MOLECULAR BASIS OF CANCER - THE HALLMARKS

Hanahan & Weinberg's Hallmarks of Cancer:

Self-sufficiency in growth signals
Insensitivity to anti-growth signals
Evading apoptosis
Limitless replicative potential (telomerase)
Sustained angiogenesis (VEGF)
Tissue invasion and metastasis
Reprogramming of energy metabolism (Warburg effect - aerobic glycolysis)
Evading immune destruction
Genome instability
Tumor-promoting inflammation

ONCOGENES

Mutations are gain-of-function (dominant - one allele affected)

Oncogene	Mechanism	Associated Cancer
RAS (KRAS, NRAS, HRAS)	GTP-binding protein; mutation → constitutively active; most common in human cancers	Pancreatic (95%), colon (50%), lung adenocarcinoma
MYC (c-myc)	Transcription factor; stimulates cell growth/proliferation	Burkitt lymphoma (t(8;14) - translocation with IgH)
N-myc	Transcription factor	Neuroblastoma (poor prognosis with amplification)
L-myc	-	Small cell lung cancer
ERBB2 (HER2/neu)	EGF receptor (EGFR family member); amplified	Breast, gastric, ovarian cancer; target of trastuzumab
EGFR (ERBB1)	EGF receptor; mutation/amplification	Lung adenocarcinoma (target of erlotinib, gefitinib)
BCR-ABL	Translocation t(9;22) Philadelphia chromosome; constitutively active tyrosine kinase	CML; target of imatinib (Gleevec)
BRAF	Serine-threonine kinase; V600E mutation most common	Melanoma (60%); target of vemurafenib
RET	Tyrosine kinase; point mutation	MEN2A, MEN2B, familial medullary thyroid carcinoma
ALK	Translocation EML4-ALK	Lung adenocarcinoma; target of crizotinib
MET	HGF receptor; amplification	Gastric, lung cancer
CYCLIN D1	Promotes G1→S transition; overexpression	Mantle cell lymphoma t(11;14), breast cancer
CDK4	Works with cyclin D; amplification	Sarcomas, melanoma

TUMOR SUPPRESSOR GENES

Mutations are loss-of-function (recessive - BOTH alleles must be lost = "two-hit hypothesis" - Knudson)

Two-hit hypothesis:

Hereditary cancers: one germline mutation (hit 1) + one somatic mutation (hit 2) → cancer at young age, bilateral/multifocal
Sporadic cancers: two somatic mutations required → cancer at older age, unilateral

Gene	Function	Associated Cancer
RB (retinoblastoma)	Transcription repressor; inhibits E2F (S-phase genes); RB-P = inactive → release E2F → S phase	Retinoblastoma, osteosarcoma
P53 (TP53)	"Guardian of the genome"; transcription factor; arrested cell cycle at G1 checkpoint; stimulates DNA repair; induces apoptosis if repair fails; mutated in ~50% of all human cancers	Li-Fraumeni syndrome (germline) → multiple tumors; colon, breast, lung, leukemia
APC	Inhibits Wnt signaling; degrades beta-catenin; loss → beta-catenin accumulates → MYC, cyclin D1 upregulation	Familial adenomatous polyposis (FAP) → colon cancer; Gardner syndrome
BRCA1/BRCA2	DNA repair (homologous recombination)	Hereditary breast/ovarian cancer; also pancreatic cancer
VHL	Ubiquitin ligase; degrades HIF-1α (prevents angiogenesis under normoxia); loss → HIF-1α accumulates → VEGF	Clear cell renal cell carcinoma; von Hippel-Lindau syndrome
NF1	GAP (GTPase-activating protein) → inactivates RAS	Neurofibromatosis type 1
NF2	Merlin (cytoskeletal protein); connects membrane to actin	Neurofibromatosis type 2 (bilateral acoustic neuromas)
PTEN	Phosphatase; inhibits PI3K/Akt pathway	PTEN hamartoma syndrome (Cowden), prostate, endometrial cancer
CDKN2A (p16/INK4A)	CDK4 inhibitor; keeps RB in active (hypophosphorylated) state	Familial melanoma, pancreatic cancer
SMAD2/SMAD4	TGF-β signaling mediators; normally inhibit cell cycle	Pancreatic (90%), colorectal cancer
WT1	Transcription factor; kidney development	Wilms tumor
DPC4 (SMAD4)	TGF-β signaling	Pancreatic cancer
PATCHED (PTCH1)	Hedgehog receptor; normally inhibits Smoothened	Basal cell carcinoma; Gorlin syndrome

DNA REPAIR GENES ("CARETAKERS")

When mutated → microsatellite instability (MSI) or chromosomal instability

MLH1, MSH2, MSH6, PMS2 (mismatch repair) → hereditary non-polyposis colorectal cancer (Lynch syndrome); also endometrial, ovarian, gastric
BRCA1/BRCA2 (homologous recombination) → hereditary breast/ovarian cancer
XPA-XPG (nucleotide excision repair) → Xeroderma pigmentosum (UV-induced skin cancer)
ATM (checkpoint kinase) → Ataxia-telangiectasia → leukemia/lymphoma + cerebellar ataxia

CARCINOGENESIS: MECHANISMS

Chemical carcinogens:

Direct-acting (do not require metabolic activation): nitrogen mustards, cyclophosphamide, nitrosoureas, acrylate
Indirect-acting (procarcinogens) require activation by P-450:
- PAH (polycyclic aromatic hydrocarbons) - cigarette smoke (benzo[a]pyrene) → lung cancer
- Aromatic amines (β-naphthylamine) → bladder cancer
- Aflatoxin B1 (Aspergillus flavus in contaminated foods) → hepatocellular carcinoma (with HBV); causes G→T mutation in codon 249 of p53
- Benzene → leukemia (AML)
- Asbestos → mesothelioma + lung cancer
- Vinyl chloride → hepatic angiosarcoma
- Nitrosamines → gastric cancer
Initiators + promoters: initiation = irreversible DNA mutation; promotion = expansion of mutated clone (reversible, requires prolonged exposure); promotion alone does NOT cause cancer

Radiation:

UV radiation (UVB most carcinogenic): causes pyrimidine dimers (T-T most common) → if not repaired by nucleotide excision repair → mutations in p53, RAS → skin cancers (SCC, BCC, melanoma)
Ionizing radiation (X-rays, gamma): DNA strand breaks → leukemia (AML, CML), thyroid, breast cancer; latency of years

Viral Carcinogens:

Virus	Mechanism	Cancer
HPV (16, 18)	E6 protein → degrades p53; E7 protein → binds RB, inactivates it	Cervical, anal, oropharyngeal, vulvar carcinoma
EBV (HHV-4)	LMP1 activates BCL-2, NF-κB	Burkitt lymphoma, Hodgkin lymphoma (mixed cellularity), nasopharyngeal carcinoma (non-keratinizing), post-transplant lymphoma
HBV/HCV	Chronic inflammation + cirrhosis → regeneration → mutations; HBX protein of HBV activates growth factors	Hepatocellular carcinoma
HTLV-1	Tax protein → activates NF-κB, cyclin D1	Adult T-cell leukemia/lymphoma (ATL)
HHV-8 (KSHV)	Encodes viral IL-6, viral BCL-2, viral cyclin D	Kaposi sarcoma; primary effusion lymphoma
Merkel cell polyomavirus	T antigen inactivates RB	Merkel cell carcinoma

Bacterial:

H. pylori → chronic gastritis → gastric adenocarcinoma + MALT lymphoma (EBV also in gastric carcinoma)

TUMOR IMMUNOLOGY

Tumor Antigens:

TSA (Tumor-Specific Antigens): unique to tumor cells; mutant RAS, p53, BCR-ABL
TAA (Tumor-Associated Antigens): present in tumor AND some normal cells
- Oncofetal antigens: AFP (hepatocellular carcinoma, germ cell tumors), CEA (colorectal, gastric, pancreatic cancer)
- Differentiation antigens: PSA (prostate), CD20 (B-cell lymphoma)

Anti-tumor effectors:

CTLs (CD8+ T cells) - most effective tumor killers; recognize MHC I + tumor peptides
NK cells - kill cells with low/absent MHC I (tumor evasion strategy backfires)
Macrophages - activated by IFN-γ → tumor cell killing
Antibodies - ADCC (antibody-dependent cell-mediated cytotoxicity)

Tumor immune evasion:

Downregulation of MHC I → avoids CTL recognition
Expression of PD-L1 → binds PD-1 on T cells → T cell anergy/exhaustion
CTLA-4 upregulation → inhibits T cell activation
TGF-β secretion → immunosuppression
FasL expression → induces apoptosis in T cells
Recruitment of Treg cells and MDSCs (myeloid-derived suppressor cells)
Basis for checkpoint inhibitor therapy: anti-PD-1 (nivolumab, pembrolizumab), anti-CTLA-4 (ipilimumab)

PARANEOPLASTIC SYNDROMES

Symptoms caused by tumor products/immune responses, NOT due to direct mass effect or metastasis:

Syndrome	Mediator	Tumor
Hypercalcemia	PTHrP (parathyroid hormone-related protein)	Squamous cell carcinoma of lung, breast cancer, myeloma
Cushing syndrome (ectopic ACTH)	ACTH	Small cell lung cancer
SIADH	ADH	Small cell lung cancer
Polycythemia (erythrocytosis)	EPO	Renal cell carcinoma, hepatocellular carcinoma, cerebellar hemangioblastoma
Hypoglycemia	IGF-2	Retroperitoneal sarcoma, hepatocellular carcinoma
Carcinoid syndrome	Serotonin	Carcinoid tumors (usually with liver mets)
Lambert-Eaton syndrome	Antibodies against presynaptic Ca2+ channels	Small cell lung cancer
Trousseau syndrome	Hypercoagulable state	Pancreatic, gastric cancer
Acanthosis nigricans	TGF-α?	Gastric, lung, uterine cancer

TUMOR GRADING AND STAGING

Grading: degree of differentiation (histologic) - based on N:C ratio, mitoses, pleomorphism

Grade I = well differentiated; Grade IV = anaplastic/undifferentiated

Staging: extent of spread - most important in prognosis

TNM staging: T (tumor size/invasion), N (lymph node involvement), M (distant metastasis)
Clinical staging (cTNM) vs. pathologic staging (pTNM)
Stage I = localized; Stage IV = distant metastasis

CHAPTER 7: IMMUNITY AND IMMUNOPATHOLOGY

INNATE vs. ADAPTIVE IMMUNITY

	Innate	Adaptive
Specificity	Non-specific; pattern recognition	Antigen-specific; enormous repertoire
Speed	Immediate (minutes-hours)	Delayed (days-weeks for primary response)
Memory	No	Yes
Cells	Neutrophils, NK cells, macrophages, dendritic cells, mast cells	T cells, B cells
Receptors	PRRs (TLRs, NLRs)	TCR, BCR (antigen-specific)

HYPERSENSITIVITY REACTIONS (Gell & Coombs)

Type I - Immediate Hypersensitivity (IgE-mediated, Anaphylactic):

1st exposure: antigen (allergen) → Th2 cells → IL-4 + IL-13 → B cells → IgE synthesis → IgE binds FcεRI on mast cells/basophils (sensitization)
2nd exposure: allergen crosslinks IgE on mast cells → degranulation + new mediator synthesis
Preformed mediators (immediate, < 30 min): histamine, tryptase, heparin, chemotactic factors (ECF-A for eosinophils, NCF for neutrophils)
Newly synthesized mediators (late phase, 2-24h after): PGD2, LTC4/D4/E4, PAF, IL-3/4/5, TNF
Effects: vasodilation, increased permeability, smooth muscle spasm, mucus secretion, eosinophil recruitment
Examples: anaphylaxis, asthma (atopic), urticaria, hay fever, food allergy
Skin test: wheal-and-flare reaction (immediate)

Type II - Antibody-Mediated Hypersensitivity:

IgG or IgM antibodies against cell surface or ECM antigens → damage by:
1. Complement-dependent cytotoxicity (MAC)
2. Opsonization + phagocytosis (C3b or IgG Fc receptor)
3. ADCC (antibody-dependent cell-mediated cytotoxicity via NK cells)
4. Antibody-mediated cellular dysfunction (anti-TSH receptor in Graves' = stimulating; anti-AChR in MG = blocking)
Examples: hemolytic transfusion reactions (ABO incompatibility), autoimmune hemolytic anemia, ITP, Goodpasture syndrome (anti-GBM), Graves' disease, myasthenia gravis, pemphigus (anti-desmoglein)

Type III - Immune Complex-Mediated Hypersensitivity:

IgG or IgM + antigen form immune complexes → deposit in vessel walls/tissues → activate complement → neutrophil influx → tissue damage
Complement-mediated: C3a/C5a → mast cell degranulation + neutrophil recruitment → release lysosomal enzymes → fibrinoid necrosis
Arthus reaction: local immune complex reaction (intradermal injection)
Serum sickness: systemic immune complex disease (horse serum, drugs)
- 7-10 days after antigen → fever, arthralgias, glomerulonephritis, urticaria, low complement
Systemic examples: SLE (anti-dsDNA complexes), post-streptococcal GN, cryoglobulinemia, hypersensitivity pneumonitis (farmer's lung, bird-fancier's lung - type III + type IV)

Type IV - Cell-Mediated (Delayed-Type) Hypersensitivity:

T-cell mediated; no antibody
CD4+ Th1 cells: sensitized by APC (dendritic cell) on 1st exposure → activated Th1 cells → IFN-γ → macrophage activation → tissue damage; peak 48-72 hours (delayed)
CD8+ CTLs: direct killing of antigen-bearing cells (viral, transplant rejection)
Mantoux (PPD) test: Type IV reaction; induration at 48-72h = positive
Examples:
- Tuberculin test (PPD) - prototype type IV
- Contact dermatitis (poison ivy, nickel) - Th1/CD8 cells
- Granulomatous inflammation (TB, sarcoidosis, fungal infections) - Th1 cells + IFN-γ
- Type 1 diabetes mellitus - CTL-mediated destruction of beta cells
- Multiple sclerosis - Th1 cells + CTLs destroy myelin

AUTOIMMUNE DISEASES (Overview)

Mechanisms of Autoimmunity:

Failure of central tolerance (thymic deletion of self-reactive T cells; bone marrow deletion of self-reactive B cells) → incomplete → escape
Molecular mimicry - microbial antigen structurally similar to self antigen → immune response also attacks self (rheumatic fever: anti-streptococcal Abs cross-react with cardiac myosin)
Bystander activation - inflammation + tissue damage → release of sequestered self-antigens → autoimmunity
Abnormal TLR signaling - TLR9 responds to self-DNA/RNA released from dying cells
Failure of peripheral tolerance: defective Treg cells (FOXP3 mutation → IPEX syndrome), defective Fas-FasL (ALPS - autoimmune lymphoproliferative syndrome)
Epitope spreading - initial autoimmune damage releases new epitopes → more autoreactive cells
Genetic factors: HLA genes most important; also PTPN22, CTLA4 polymorphisms

HLA Associations (exam favorites):

HLA-B27: ankylosing spondylitis, reactive arthritis (Reiter), IBD arthropathy, psoriatic arthritis
HLA-DR2: SLE, MS, narcolepsy, Goodpasture
HLA-DR3: SLE, Sjögren's, type 1 DM, CAH (21-hydroxylase def.)
HLA-DR4: RA, type 1 DM
HLA-DR5: pernicious anemia, Hashimoto thyroiditis
HLA-DQ2/DQ8: Celiac disease (strongest HLA association)
HLA-DR3/DR4 heterozygote: highest risk for type 1 DM

CHAPTER 8: GENETIC AND PEDIATRIC DISEASES

MUTATIONS AND GENETIC DISEASE

Types of mutations:

Point mutations: single nucleotide change
- Missense → different amino acid (e.g., HbS - valine for glutamate at position 6 of β-globin)
- Nonsense → premature stop codon → truncated protein
- Silent → same amino acid (synonymous)
Frameshift: insertion/deletion of non-multiple-of-3 nucleotides → abnormal downstream sequence + premature stop
Trinucleotide repeat expansions: unstable repetitive sequences that expand with cell division → anticipation (earlier onset in subsequent generations)
- Huntington: CAG repeats in HTT; dominant; striatum (caudate) degeneration; chorea, dementia, psychiatric
- Fragile X (FMR1): CGG repeats; X-linked dominant; most common inherited intellectual disability in males; FMRP protein (synaptic plasticity); premutation carrier females → primary ovarian failure; carrier males → tremor/ataxia syndrome
- Myotonic dystrophy: CTG repeats in DMPK; dominant; myotonia, cataracts, testicular atrophy
- Friedreich ataxia: GAA repeats; recessive; cerebellar ataxia + cardiomyopathy

MENDELIAN DISORDERS

Autosomal Dominant (AD):

Usually structural protein or receptor defects; 50% risk to offspring
Key: new mutations, variable expressivity, incomplete penetrance
Examples:
- Marfan syndrome: FBN1 (fibrillin-1) gene; connective tissue → tall stature, long limbs, arachnodactyly, subluxation of lens (upward), aortic aneurysm/dissection, mitral valve prolapse
- EDS (Ehlers-Danlos syndrome): collagen or lysyl hydroxylase gene defects; hyperextensible joints, fragile skin
- Osteogenesis imperfecta: COL1A1/COL1A2; blue sclerae, brittle bones, hearing loss; Type II = lethal
- Achondroplasia: FGFR3 (constitutively active); most common cause of dwarfism; normal trunk + shortened limbs; 80% new mutations
- Familial hypercholesterolemia: LDL receptor defect; premature atherosclerosis, xanthomas, xanthelasmas; homozygous = MI in childhood
- Huntington: see above
- NF1/NF2: see above
- Von Willebrand disease: most common inherited bleeding disorder; VWF deficiency/dysfunction
- Adult PKD (ADPKD): PKD1 (85%), PKD2; polycystin proteins; bilateral renal cysts; hepatic cysts; berry aneurysms

Autosomal Recessive (AR):

Usually enzyme defects; often consanguinity; 25% risk in each pregnancy (heterozygotes are carriers)
Examples:
- Cystic Fibrosis: CFTR gene (chromosome 7); ΔF508 most common mutation; Cl- channel defect → thick mucus; lung disease (P. aeruginosa), pancreatic insufficiency, infertility (males: bilateral absence of vas deferens), meconium ileus; sweat chloride > 60 mEq/L = diagnostic
- Sickle Cell Anemia (HbSS): valine for glutamate at position 6 of β-globin → HbS polymerizes when deoxygenated → sickle cells → hemolysis + vaso-occlusion
- Thalassemias: α-thalassemia (deletion of α-globin genes on chr 16); β-thalassemia (point mutations → β+/β0)
- PKU: PAH deficiency → phenylalanine accumulates → intellectual disability + fair skin/hair (tyrosine also can't be made); treat with phenylalanine-restricted diet; maternal PKU → fetal damage
- Galactosemia: galactose-1-phosphate uridyl transferase deficiency; galactose-1-P accumulates → liver damage, cataracts, intellectual disability
- Lysosomal Storage Diseases (see table below)
- Glycogen Storage Diseases: see below
- Wilson disease: ATP7B (copper transporter) → copper accumulates in liver, brain, cornea (Kayser-Fleischer rings)
- Hemochromatosis: HFE gene (C282Y most common) → iron overload → liver cirrhosis, diabetes, cardiomyopathy, arthropathy, hypogonadism; Prussian blue stain++

X-Linked Recessive (XLR):

Carrier females (1 mutant allele); affected males (hemizygous); daughters of affected males = obligate carriers
Examples:
- Hemophilia A: Factor VIII deficiency; prolonged PTT, normal PT; treat with recombinant Factor VIII
- Hemophilia B (Christmas disease): Factor IX deficiency
- G6PD deficiency: episodic hemolysis (Heinz bodies - oxidized Hb) triggered by oxidative stress (primaquine, fava beans, infection); favism; most common RBC enzyme deficiency
- Duchenne MD: DMD (dystrophin); frameshift mutation → absent dystrophin; pseudohypertrophy of calves, Gower's sign; elevated CK; death in 20s (respiratory failure)
- Becker MD: in-frame mutation → truncated but functional dystrophin; milder course
- Fragile X: see above

LYSOSOMAL STORAGE DISEASES (HIGH-YIELD!)

Disease	Enzyme Deficiency	Substrate	Key Features
Gaucher (most common LSD)	Glucocerebrosidase (β-glucosidase)	Glucocerebroside	Hepatosplenomegaly, bone marrow involvement (Erlenmeyer flask deformity), "crinkled tissue paper" macrophages; Types 1, 2, 3
Niemann-Pick (A+B)	Sphingomyelinase	Sphingomyelin	Cherry-red spot (Type A), hepatosplenomegaly, Type A = neurologic decline (fatal by age 3)
Niemann-Pick C	Cholesterol transport (NPC1/NPC2)	Cholesterol (sequestered in lysosomes)	Vertical gaze palsy, dementia, hepatosplenomegaly; not really sphingolipidosis
Tay-Sachs	Hexosaminidase A	GM2 ganglioside	Cherry-red spot, progressive neurodegeneration, blindness; no organomegaly
Fabry	α-Galactosidase A	Globotriaosylceramide (Gb3)	X-linked; angiokeratomas, renal failure, cardiomyopathy, stroke
Krabbe	Galactocerebrosidase	Galactocerebroside	Globoid cells, demyelination, peripheral neuropathy
Metachromatic leukodystrophy	Arylsulfatase A	Sulfatide (cerebroside sulfate)	Demyelination; metachromatic granules in urine + tissues
Hurler (MPS I)	α-L-iduronidase	Heparan/dermatan sulfate	Corneal clouding, hepatosplenomegaly, coarse facies, intellectual disability, gargoylism
Hunter (MPS II)	Iduronate sulfatase	Heparan/dermatan sulfate	X-linked; similar to Hurler but NO corneal clouding, less severe
Pompe (GSD II)	α-1,4-glucosidase (acid maltase)	Glycogen	Cardiomegaly, hypotonia, hepatomegaly; ONLY GSD with lysosomal storage
Wolman	Lysosomal acid lipase	Cholesterol esters + TG	Adrenal gland calcification; fatal in infancy

CHROMOSOMAL DISORDERS

Numerical Abnormalities:

Syndrome	Karyotype	Key Features
Down syndrome (Trisomy 21)	47,XX/XY +21	Most common chromosomal disorder; most common cause of intellectual disability (chromosomal); flat facies, epicanthal folds, single palmar crease, Brushfield spots; ASD/VSD; duodenal atresia; increased risk of ALL (children) and AML (newborns); Alzheimer's at early age (APP on chr 21); Hirschsprung's
Edwards syndrome (Trisomy 18)	47,XX/XY +18	Low birth weight; rocker-bottom feet; clenched fists (overlapping fingers); VSD; intellectual disability; death within 1 year
Patau syndrome (Trisomy 13)	47,XX/XY +13	Holoprosencephaly; cyclopia/proboscis; cleft lip/palate; polydactyly; rocker-bottom feet; death within 1 year
Klinefelter syndrome	47,XXY (most common)	Male; most common cause of hypogonadism in males; tall, long legs, gynecomastia; small firm testes; azoospermia; low testosterone, high FSH/LH; Barr body present
Turner syndrome	45,X (most common)	Female; short stature; streak ovaries → primary amenorrhea; webbed neck; shield chest; coarctation of aorta; cystic hygroma (detected antenatally); lymphedema; horseshoe kidney; NO Barr body
47,XYY	47,XYY	Tall males; normal fertility; slightly increased behavioral issues
47,XXX	47,XXX	Females; usually normal phenotype; 2 Barr bodies

IMPRINTING DISORDERS

Genomic imprinting: silencing of one allele based on parent of origin (methylation)

Prader-Willi syndrome: deletion of paternally inherited region of chromosome 15q11-13 (or maternal disomy of chr 15); features: hypotonia at birth, hyperphagia → obesity, hypogonadism, mild intellectual disability
Angelman syndrome: deletion of maternally inherited region of chromosome 15q11-13 (or paternal disomy of chr 15); features: severe intellectual disability, seizures, "happy puppet" (paroxysmal laughter), gait ataxia; UBE3A gene (expressed only from maternal allele in brain)

Mnemonic: PAW-MAW

Prader-Willi = Paternal deletion (or maternal disomy)
Angelman = Maternal deletion (or paternal disomy)

AMYLOIDOSIS

DEFINITION AND CLASSIFICATION

Amyloid: abnormal protein fibrils deposited in extracellular space; all share:

β-pleated sheet secondary structure
Congo red stain → apple-green birefringence under polarized light
SAP (serum amyloid P component) and apolipoprotein E are always present

Types of Amyloid:

Type	Amyloid Protein	Precursor	Disease
AL	Immunoglobulin light chains (λ>κ)	Plasma cell dyscrasias	Primary amyloidosis (multiple myeloma)
AA	SAA (serum amyloid A)	Chronic inflammation	Secondary amyloidosis (RA, TB, FMF, osteomyelitis)
Aβ (A4)	Aβ peptide	APP (amyloid precursor protein)	Alzheimer's disease; Down syndrome
ATTR	Transthyretin (TTR)	Transthyretin	Senile systemic amyloidosis (normal TTR, elderly); familial amyloid polyneuropathy (mutant TTR, Portuguese families)
Aβ2M	β2-microglobulin	β2-microglobulin (filtered by kidney)	Hemodialysis-associated amyloidosis (carpal tunnel)
AIAPP	Islet Amyloid Polypeptide (IAPP)	IAPP (from islet B cells)	Type 2 Diabetes (islets of Langerhans)
AScr	Prion protein (PrPsc)	PrP	Prion diseases (CJD, GSS, kuru, scrapie)
ANF (AANF)	Atrial natriuretic factor	ANF	Isolated cardiac amyloidosis

Morphology of Amyloid:

H&E: homogeneous, acellular eosinophilic material in walls of vessels, glomeruli, between parenchymal cells
Congo red: brick-red; apple-green birefringence under polarized light
EM: non-branching fibrils, 7.5-10 nm diameter

Organs Affected in Systemic Amyloidosis:

Kidney (most common in secondary AA and AL): glomerular deposition → proteinuria → nephrotic syndrome; most common cause of death in secondary amyloidosis
Liver: hepatomegaly; amyloid in Space of Disse
Spleen: "sago spleen" (follicular amyloid - white nodules on cut surface) or "lardaceous spleen" (diffuse amyloid)
Heart: restrictive cardiomyopathy; low voltage on ECG; "ground glass" appearance
Tongue: macroglossia (in AL amyloid/myeloma)
Peripheral nerves: peripheral neuropathy (familial ATTR, AL)

QUICK-REFERENCE SUMMARY TABLE: KEY STAINS IN PATHOLOGY

Stain	Target	Color
H&E	Nuclei/Cytoplasm	Purple/Pink
PAS (Periodic Acid-Schiff)	Glycogen, glycoproteins, fungi, basement membranes	Magenta/Pink
Ziehl-Neelsen (AFB)	Mycobacteria (TB, leprosy)	Red (acid-fast) on blue background
Congo red	Amyloid	Apple-green birefringence (polarized)
Prussian blue (Perl's)	Iron (hemosiderin, ferritin)	Blue
Oil Red O (Sudan)	Lipids	Red (requires fresh/frozen sections)
Masson's trichrome	Collagen/fibrosis	Blue-green (collagen); red (muscle)
Reticulin (Gordon-Sweets)	Reticular fibers (type III collagen), tumor architecture	Black
Von Kossa	Calcium (phosphates)	Black
Alizarin Red	Calcium (direct)	Red
GMS (Grocott-Gomori Methenamine Silver)	Fungi	Black
Mucicarmine	Mucin, Cryptococcus capsule	Red/Pink
Giemsa	Hematology, malaria, H. pylori	Various
Toluidine blue	Mast cells (metachromatic)	Purple-red on blue background
Alcian blue	Acid mucins, GAGs	Blue
Thioflavin T	Amyloid (fluorescence)	Bright yellow-green
Luxol fast blue	Myelin	Blue-green

FINAL RAPID REVIEW - EXAM FAVORITES

Cell Death - Key Comparisons

Feature	Necrosis	Apoptosis
Stimulus	Pathologic	Physiologic or pathologic
Cell size	Enlarged (swelling)	Reduced (shrinkage)
Nucleus	Pyknosis → karyorrhexis → karyolysis	Condensation, fragmentation
Plasma membrane	Disrupted	Intact; blebbing
Cellular contents	Released → inflammation	Enclosed in apoptotic bodies
Inflammation	YES	NO
DNA	Random fragmentation	Internucleosomal (laddering)
Adjacent cells	Multiple (group)	Single cells

Necrosis Types - One-Liners

Coagulative = most organs; dead cells persist as ghost outlines
Liquefactive = brain ischemia; bacterial abscesses → pus
Caseous = TB; cheese-like with granuloma
Fat necrosis = pancreatitis; chalky white saponification
Fibrinoid = vessel walls in vasculitis; immune complex deposition
Gangrenous = limbs; dry (coagulative) vs wet (+ liquefactive)

Mediators - Source and Action

Histamine → vasodilation + permeability (immediate)
C5a → best chemotactic + anaphylatoxin
LTB4 → best lipid chemotactic
LTC4/D4/E4 (SRS-A) → bronchoconstriction
IL-8 → neutrophil chemotaxis
IL-1 + TNF → fever + endothelial activation
TGF-β → fibrosis + anti-inflammatory
IFN-γ → macrophage activation → classical M1
PGE2 → fever + pain + vasodilation
TXA2 → vasoconstriction + platelet aggregation
PGI2 → opposite of TXA2

Oncogenes - One Liners

RAS - most common oncogene mutation in all cancers
P53 - most common tumor suppressor mutated in cancers
BCR-ABL/t(9;22) - CML → imatinib
HER2 - breast cancer → trastuzumab
BRAF V600E - melanoma → vemurafenib
EGFR - lung adenocarcinoma → erlotinib
c-myc/t(8;14) - Burkitt lymphoma
RB - retinoblastoma; paradigm for two-hit hypothesis
APC - FAP/colon cancer; Wnt pathway

Amyloid - Quick Memory

AL = myeloma (light chains)
AA = chronic inflammation (serum amyloid A)
Aβ = Alzheimer's (APP)
ATTR = senile cardiac / familial neuropathy
ALL stain: Congo red → apple-green birefringence under polarized light

Good luck on your exam tomorrow, Waqas! You've got this. This revision covers every major topic in General Pathology from Robbins - Cell Injury, Necrosis, Apoptosis, Inflammation (Acute + Chronic + Granulomatous), Tissue Repair, Hemostasis/Thrombosis/Embolism, Shock, Neoplasia (Oncogenes + Tumor Suppressors + Carcinogenesis + Metastasis + Paraneoplastic), Hypersensitivity, Autoimmunity, Genetic Diseases, Lysosomal Storage Diseases, and Amyloidosis - with all the key tables, mechanisms, and one-liners you need.

Robbins & Kumar Basic Pathology, Blocks 1-8
Robbins, Cotran & Kumar Pathologic Basis of Disease

make pdf of above allong with exact diaghrams of robbin

Reading File

Finding Sources

Reading File

Running Command

grep -n "cdn.orris.care" /textbooks/9780323790185/9780323790185_block1.md | head -60

Finding Sources

Running Command

ls -la /tmp/workspace/ 2>/dev/null || mkdir -p /tmp/workspace && echo "created"

Running Command

mkdir -p /tmp/workspace/waqas-pathology && echo "directory ready"

Running Command

mkdir -p /tmp/workspace/waqas-pathology && ls /tmp/workspace/waqas-pathology

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