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“ behave like an expert pathologist from now on and explain me the following topics according to 10 marks MBBS 2 year pathology under the following headings: Definition, etiology, pathogenesis, gross and microscopy and also keep it easy for quick grasping ”

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Reading File

All 36 topics from both your images are now covered. Here's a quick orientation guide:

HOW TO USE THESE NOTES FOR 10-MARK ANSWERS

Structure your answer always as:

Definition (2-3 lines) - 1 mark
Etiology (bullet points) - 2 marks
Pathogenesis (sequential steps/flow) - 3 marks
Gross findings (what you see with naked eye) - 2 marks
Microscopy (what you see under microscope) - 2 marks

Topics covered from your list:

✅ Acute & Chronic Inflammation (SAQ & LAQ)
✅ Necrosis & Apoptosis
✅ All types of Anemia + Classification + Lab diagnosis
✅ Hyperemia vs Congestion
✅ Iron Metabolism & Disorders
✅ Hypersensitivity (all 4 types + differences)
✅ Tumor Markers + Clinical use
✅ Phases of Wound Healing
✅ Leukemoid reaction vs Leukemia
✅ Reversible vs Irreversible cell injury
✅ Normal Hemostasis + Coagulation tests
✅ Transfusion reactions (indications + reactions)
✅ Neoplasia + Molecular basis of Carcinogenesis
✅ Dysplasia + Carcinoma in situ
✅ Granulomatous inflammation + Giant cells
✅ Edema (etiopathogenesis)
✅ Platelet disorders + Classification
✅ Shock
✅ Calcification (Dystrophic vs Metastatic)
✅ Generalised Lymphadenopathy
✅ Multiple Myeloma
✅ ESR vs CRP
✅ Metaplasia
✅ Thrombocytopenia
✅ Chemical mediators of inflammation
✅ Fate of Thrombus
✅ Primary & Secondary Amyloidosis
✅ Embolism (SAQ)
✅ Cellular Adaptations
✅ Haemophilia + Types
✅ Infarction - Factors
✅ Red vs White Infarct
✅ Hodgkin's vs Non-Hodgkin's Lymphoma
✅ Leukemias (Define + whole)
✅ Gangrene (Dry vs Wet)
✅ Metastasis (Routes + Pathogenesis)

Good luck with your exams! 🎯

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I can clearly see both lists - these are Systemic Pathology topics. Let me cover all of them comprehensively right away.

🫀 SYSTEMIC PATHOLOGY - MBBS 2nd Year Important Topics

Format: Definition → Etiology → Pathogenesis → Gross → Microscopy Written for 10-mark answers | Quick grasp format

1. MYOCARDIAL INFARCTION (MI)

Definition: Ischemic coagulative necrosis of myocardium due to prolonged occlusion of coronary artery supply (usually >20-40 min of ischemia).

Etiology:

Atherosclerosis + plaque rupture + thrombosis (90% of cases)
Coronary artery spasm (Prinzmetal angina)
Embolism to coronary arteries
Vasculitis (rare)

Risk factors: Hypertension, diabetes, smoking, hyperlipidemia, family history, obesity

Pathogenesis:

Atherosclerotic plaque rupture/fissure → platelet aggregation + thrombus formation → complete coronary occlusion → cessation of blood flow → ATP depletion within 30 min → irreversible cell injury → coagulative necrosis

Types:

STEMI (transmural): Full thickness - plaque rupture + complete occlusion
NSTEMI/NQMI (subendocardial): Inner 1/3 only - incomplete occlusion or demand ischemia

Temporal Gross Changes:

Time	Gross Finding
0-12 hrs	No change (invisible)
12-24 hrs	Pale, yellow area; soft
1-3 days	Yellow-white area with hyperemic border
3-7 days	Yellow-white, soft center; red hyperemic rim (most vulnerable to rupture!)
1-2 weeks	Pale yellow, depressed
2-8 weeks	Gray-white fibrous scar forming
>2 months	White, firm, contracted scar

Temporal Microscopy Changes:

Time	Microscopy
0-6 hrs	Wavy fibers, stretched myocytes
6-24 hrs	Coagulative necrosis begins, eosinophilic cytoplasm, loss of nuclei
1-3 days	Neutrophil infiltration (peak at 2 days)
3-7 days	Macrophage infiltration, phagocytosis of dead cells
1-2 weeks	Granulation tissue (capillaries + fibroblasts)
>2 months	Collagen scar (acellular, pale pink)

Lab markers (Cardiac biomarkers):

Troponin I/T - most sensitive + specific; rises 3-6 hrs, peaks 24 hrs, stays elevated 7-10 days
CK-MB - rises 4-6 hrs, peaks 24 hrs, returns to normal in 48-72 hrs
LDH - rises late (24-48 hrs), stays elevated 10-14 days
Myoglobin - first to rise (2 hrs) but not specific

Complications: Arrhythmia (most common early cause of death), Rupture of free wall/papillary muscle/IVS, Fibrinous pericarditis, Dressler syndrome (autoimmune pericarditis), Mural thrombus, Ventricular aneurysm

2. BARRETT'S ESOPHAGUS

Definition: Metaplastic replacement of normal stratified squamous epithelium of the distal esophagus by specialized intestinal-type columnar epithelium (with goblet cells), as a consequence of chronic gastroesophageal reflux disease (GERD). It is a premalignant condition (risk of esophageal adenocarcinoma).

Etiology:

Chronic GERD (reflux of acid + bile) - main cause
Obesity, hiatus hernia
Smoking, alcohol

Pathogenesis:

Chronic acid exposure → Repeated injury to squamous cells → Healing by stem cell reprogramming → Columnar intestinal metaplasia better survives acid → Barrett's esophagus → Dysplasia → Adenocarcinoma

Gross:

Salmon-pink/red velvety mucosa in distal esophagus (vs normal pale squamous mucosa)
"Tongue-like" projections of red mucosa extending from Z-line upward
Located in distal esophagus (>3 cm above GEJ)

Microscopy:

Replacement of squamous epithelium by columnar epithelium with goblet cells (intestinal metaplasia - HALLMARK)
Goblet cells: Pale blue/lavender vacuolated cells on H&E
Dysplasia (low or high grade) may be superimposed
Alcian blue stain highlights goblet cells (acid mucin - blue)

Risk: 30-40x increased risk of esophageal adenocarcinoma (compared to normal population)

3. PNEUMONIA

Definition: Acute inflammation and consolidation (solidification) of lung parenchyma due to infection or other causes.

Etiology:

Type	Organism
Lobar pneumonia	Streptococcus pneumoniae (Pneumococcus) - most common
Bronchopneumonia	S. aureus, Klebsiella, H. influenzae, gram-negatives (hospital-acquired)
Atypical/Interstitial	Mycoplasma (most common atypical), Chlamydia, Legionella, viruses
Aspiration	Mixed oral flora, anaerobes

Pathogenesis (Lobar Pneumonia - 4 Stages):

Stage 1 - Congestion (Day 1-2):

Bacteria multiply → vascular engorgement → protein-rich edema fluid fills alveoli

Stage 2 - Red Hepatization (Day 2-4):

Alveoli packed with RBCs, fibrin, neutrophils → lung feels like liver (hepatization), red color

Stage 3 - Grey Hepatization (Day 4-8):

RBCs lyse → fibrin + neutrophils remain → grey color, firm

Stage 4 - Resolution (Day 8+):

Macrophages clear exudate → normal structure restored (most favorable)

Gross:

Lobar: Entire lobe consolidated, airless, firm, liver-like; gray or red depending on stage
Bronchopneumonia: Multiple patchy consolidations, scattered throughout lung

Microscopy:

Red hepatization: Alveoli filled with RBCs + fibrin + PMNs; alveolar septa intact
Grey hepatization: Fibrin meshwork + neutrophils + macrophages; RBCs absent
Resolution: Macrophages phagocytosing fibrin; re-aeration of alveoli
Bronchopneumonia: Peribronchial exudate, patchy distribution, alveolar PMN infiltrate

4. OVARIAN TUMORS

Definition: Neoplastic growths arising from the ovary, classified by tissue of origin.

Classification:

Type	Origin	%	Examples
Surface Epithelial	Coelomic epithelium	65-70%	Serous, Mucinous, Endometrioid, Clear cell, Brenner
Germ Cell	Primordial germ cells	15-20%	Teratoma, Dysgerminoma, Yolk sac tumor
Sex Cord-Stromal	Stromal/Sex cord cells	5-10%	Granulosa cell tumor, Thecoma, Fibroma
Metastatic	From GI, breast, uterus	5%	Krukenberg tumor (from stomach)

Serous Cystadenoma/Carcinoma (Most common ovarian tumor):

Etiology: BRCA1/BRCA2 mutations (hereditary), nulliparity, early menarche, late menopause, PCOS

Pathogenesis: Coelomic epithelium → inclusion cysts → neoplastic transformation → TP53 mutations (high grade) or KRAS/BRAF (low grade)

Gross:

Serous cystadenoma: Smooth-walled unilocular cyst, serous fluid, bilateral in 20-30%
Serous carcinoma: Irregular, solid + cystic, papillary projections, bilateral, calcified foci
Mucinous: Multilocular, large cyst filled with thick mucin, usually unilateral

Microscopy:

Serous tumor: Papillary structures lined by tubal-type epithelium (ciliated columnar cells); Psammoma bodies (concentric calcifications) - characteristic
Mucinous tumor: Tall columnar cells with basal nuclei + apical mucin vacuoles; resembles intestinal epithelium
Granulosa cell tumor: Call-Exner bodies (rosette arrangements of granulosa cells around PAS+ material) - PATHOGNOMONIC

Tumor markers:

CA-125: Serous carcinoma
AFP, hCG: Germ cell tumors
Inhibin: Granulosa cell tumor

5. NEPHROTIC SYNDROME

Definition: A clinical syndrome characterized by: Proteinuria (>3.5 g/day in adults), Hypoalbuminemia, Edema, Hyperlipidemia + Lipiduria (frothy urine).

Etiology:

Primary (Idiopathic)	Secondary
Minimal Change Disease (most common in children)	Diabetes (Diabetic nephropathy)
Focal Segmental Glomerulosclerosis (most common in adults/Black race)	SLE (Membranous nephropathy)
Membranous nephropathy (most common in adults overall)	Amyloidosis
Membranoproliferative GN	Hepatitis B/C

Pathogenesis:

Loss of polyanion (heparan sulfate) from GBM → Loss of charge barrier → Proteinuria → Low albumin → Low oncotic pressure → Edema; Liver compensates → Lipoprotein synthesis → Hyperlipidemia → Lipiduria

Gross: Kidneys may be enlarged, pale; frothy protein-rich urine

Microscopy by type:

Minimal Change Disease (MCD):

LM: Normal (hence the name!)
EM: Fusion/effacement of podocyte foot processes (HALLMARK)
IF: Negative
Responds to steroids (excellent prognosis)

Membranous Nephropathy:

LM: Thickened GBM ("spike and dome" pattern on silver stain) - subepithelial deposits
EM: Electron-dense subepithelial deposits
IF: Granular IgG + C3 along GBM

Focal Segmental Glomerulosclerosis (FSGS):

LM: Focal (some glomeruli) and segmental (part of glomerulus) sclerosis + hyalinosis
EM: Foot process effacement
IF: Focal IgM + C3

Membranoproliferative GN:

LM: Lobular glomeruli, mesangial proliferation, tram-track/double contour of GBM
IF: C3 ± IgG in granular pattern

6. OSTEOSARCOMA

Definition: Malignant bone-forming tumor in which the neoplastic cells produce osteoid (immature bone) or bone directly.

Etiology:

Most common primary malignant bone tumor in children/adolescents
Peak age: 10-20 years
RB gene mutation (hereditary retinoblastoma patients - 500x higher risk)
p53 mutations
Paget's disease (older adults - secondary osteosarcoma)
Previous radiation

Pathogenesis:

RB/p53 mutations → uncontrolled osteoblast proliferation → production of malignant osteoid + destruction of cortex → periosteal reaction → metastasis (mainly to lungs via hematogenous route)

Location: Metaphysis of long bones (distal femur > proximal tibia > proximal humerus) - "Around the knee" (60%)

Gross:

Large, destructive metaphyseal mass
Gray-white, gritty (due to osteoid)
Cortical destruction
Soft tissue extension
Codman's triangle: Periosteal elevation at margins of tumor (reactive periosteum)

Microscopy:

Pleomorphic malignant stromal cells (sarcomatous stroma)
Osteoid (pink, lace-like material) produced by tumor cells - DIAGNOSTIC
High mitotic rate, abnormal mitoses
Hemorrhage and necrosis
Cartilage may be present (osteochondrosarcoma variant)

X-ray findings (for completeness):

Bone destruction + new bone formation
Sunburst pattern (perpendicular spicules of new bone)
Codman's triangle (periosteal elevation)

7. FATTY LIVER CHANGES (HEPATIC STEATOSIS)

Definition: Abnormal accumulation of fat (mainly triglycerides) within hepatocytes, >5% of liver weight. Also called hepatic steatosis.

Etiology:

Alcoholic: Chronic alcohol excess (most common cause in developed countries)
Non-Alcoholic Fatty Liver Disease (NAFLD): Obesity, diabetes type 2, metabolic syndrome, hyperlipidemia
Other: Starvation, TPN, drugs (corticosteroids, amiodarone, methotrexate), pregnancy (acute fatty liver of pregnancy)

Pathogenesis (Alcohol-induced):

Alcohol → Acetaldehyde + NADH (by alcohol dehydrogenase) → High NADH ratio → Blocks beta-oxidation of fatty acids → Fat accumulates in hepatocytes + Increased fatty acid synthesis → Steatosis

NAFLD Pathogenesis:

Insulin resistance → Increased FFA mobilization from adipose → Hepatic fat accumulation → Oxidative stress → Inflammation → NASH → Fibrosis/Cirrhosis ("two-hit hypothesis")

Gross:

Enlarged liver (hepatomegaly)
Yellow-orange color (due to fat)
Greasy/soft texture
Rounded edges

Microscopy:

Macrovesicular steatosis (most common): Large fat vacuole displaces nucleus to periphery (like signet ring) - alcoholic/NAFLD
Microvesicular steatosis: Multiple small fat droplets, nucleus remains central - acute fatty liver of pregnancy, Reye's syndrome (more serious)
Special stain: Oil Red O (on frozen section) - fat stains red
Alcoholic Hepatitis additional features: Mallory-Denk bodies (eosinophilic cytoplasmic aggregates of intermediate filaments), neutrophil infiltration, ballooning degeneration

8. BRONCHOGENIC CARCINOMA + PARANEOPLASTIC SYNDROME

Definition: Primary malignant tumor arising from the bronchial epithelium (or bronchiolar/alveolar epithelium).

Classification + Etiology:

Type	%	Key Feature	Etiology
Squamous Cell Carcinoma	25-30%	Central; Cavitates; Keratinization; PTHrP (hypercalcemia)	Smoking (strongest)
Adenocarcinoma	35-40% (most common)	Peripheral; TTF-1+; EGFR mutation (target of therapy)	Smoking, non-smokers too
Small Cell (SCLC)	15-20%	Central; Most aggressive; MOST paraneoplastic syndromes; Never resected	Smoking
Large Cell	10%	Peripheral; Anaplastic; Diagnosis of exclusion	Smoking

Pathogenesis:

Carcinogens (tobacco smoke, asbestos, radon) → DNA damage → Mutations in KRAS, EGFR, p53, RB → Squamous metaplasia → Dysplasia → CIS → Invasive carcinoma

Paraneoplastic Syndromes (especially SCLC):

Syndrome	Mechanism	Tumor Type
SIADH (dilutional hyponatremia)	ADH secretion by tumor	SCLC
Cushing's syndrome	ACTH secretion	SCLC
Hypercalcemia	PTHrP	Squamous cell
Lambert-Eaton Syndrome	Anti-VGCC antibodies	SCLC
Clubbing + HPOA	Unknown	Adenocarcinoma, Squamous
Carcinoid syndrome	5-HT	Carcinoid tumor

Gross:

Squamous/SCLC: Central, endobronchial, cavitating mass
Adenocarcinoma: Peripheral nodule, scar carcinoma (from old scars)
All: Gray-white firm mass, necrosis, hemorrhage

Microscopy:

Squamous: Keratinization (keratin pearls), intercellular bridges, pink squamous cells
Adenocarcinoma: Glandular acini, mucin production, TTF-1 positive
SCLC: Small cells ("oat cells"), scant cytoplasm, dark nuclei, salt-and-pepper chromatin, nuclear molding, no nucleoli, necrosis; Azzopardi effect (DNA encrustation on vessel walls)
Large cell: Sheets of undifferentiated large cells, abundant cytoplasm, no keratinization/glands

9. TUBERCULOSIS (TB)

Definition: Chronic granulomatous infectious disease caused by Mycobacterium tuberculosis, characterized by caseating granuloma formation.

Etiology:

Mycobacterium tuberculosis (acid-fast bacillus, aerobic, slow-growing)
Spread: Airborne droplets
Risk factors: HIV/AIDS, malnutrition, diabetes, poverty, overcrowding, immunosuppression

Pathogenesis:

Primary TB (Ghon Complex):

First exposure → Bacilli inhaled → Phagocytosed by alveolar macrophages → Macrophages cannot kill mycobacteria (waxy mycolic acid capsule) → Bacilli multiply intracellularly → T-cell activation (2-8 weeks) → Granuloma formation

Secondary (Reactivation) TB:

Latent TB reactivates (immunosuppression) → Usually apices of lung → Progressive caseation → Cavity formation → Spread

Ghon Complex = Subpleural focus (Ghon focus) + Ipsilateral hilar lymph node enlargement

Gross:

Caseous necrosis: Cheese-like, yellow-white, crumbly material
Ghon focus: Subpleural consolidation
Progressive disease: Cavities (air-filled spaces) in upper lobes
Healed: Calcified Ghon complex (Ranke complex)
Military TB: Multiple 1-2 mm pale yellow granules throughout lung ("millet seeds")

Microscopy - CLASSIC:

Caseating granuloma: Central eosinophilic (pink) amorphous caseous necrosis
Epithelioid cells (activated macrophages with elongated nuclei, abundant pink cytoplasm)
Langhans giant cells (nuclei arranged in horseshoe/peripheral pattern at margins)
Outer zone: Lymphocytes + fibroblasts (fibrous rim)
ZN (Ziehl-Neelsen) stain: Red/pink acid-fast bacilli on blue background

10. CARCINOMA CERVIX (CA CERVIX)

Definition: Malignant neoplasm arising from the epithelium of the uterine cervix, usually at the squamocolumnar junction (transformation zone).

Etiology:

HPV (Human Papillomavirus) - most important cause; HPV types 16, 18 (high-risk)
HPV 16 → Squamous cell carcinoma (more common)
HPV 18 → Adenocarcinoma
Multiple sexual partners, early sexual activity, smoking, immunosuppression, multiparity

Pathogenesis:

HPV infects transformation zone → HPV E6 protein degrades p53 → HPV E7 protein inactivates RB gene → Loss of tumor suppressors → Uncontrolled cell proliferation → CIN I → CIN II → CIN III → CIS → Invasive carcinoma

Progression: Normal → CIN I (mild dysplasia) → CIN II (moderate) → CIN III (severe/CIS) → Invasive carcinoma

Gross:

Early: Not visible (detected by Pap smear)
Late: Ulcerative/fungating/infiltrating mass at cervix
Barrel-shaped cervix in advanced disease
Bleeds easily on touch

Microscopy:

Squamous cell carcinoma (80%): Nests of squamous cells with keratin pearls, intercellular bridges, invasive through BM
Adenocarcinoma (15-20%): Glandular pattern, mucin-secreting cells
CIN I: Dysplastic cells in lower 1/3 of epithelium; koilocytes (HPV-infected cells - perinuclear halo + hyperchromatic irregular nucleus)
CIN III/CIS: Full thickness dysplasia, BM intact

Koilocyte = HPV cytopathic effect: enlarged cell with perinuclear halo ("halo cells") - PATHOGNOMONIC of HPV

11. ATHEROSCLEROSIS

Definition: A chronic inflammatory disease of large and medium arteries characterized by the formation of fibro-fatty plaques (atheromas) in the intima, leading to luminal narrowing and complications.

Etiology (Risk factors):

Non-modifiable: Age, male sex, family history, genetic factors
Modifiable: Hypertension, hyperlipidemia (LDL), diabetes, smoking, obesity, sedentary lifestyle

Pathogenesis - "Response to Injury" Hypothesis:

Endothelial injury (by LDL, HTN, smoking) → Endothelial dysfunction
Monocyte adhesion to endothelium → Migrate to intima → Become Macrophages
Macrophages take up oxidized LDL (via scavenger receptors) → become Foam cells
Foam cells accumulate → Fatty streak (earliest lesion)
Smooth muscle cells migrate from media → Proliferate in intima → Produce collagen (fibrous cap)
Fibrous plaque forms (lipid core + fibrous cap)
Plaque rupture → thrombosis → MI/stroke

Gross:

Fatty streak: Flat, yellow streaks on intimal surface (earliest lesion, reversible)
Fibrous plaque (atheroma): Raised, white/yellow elevated lesion; may be calcified
Complicated plaque: Ulceration, calcification, hemorrhage into plaque, overlying thrombus

Microscopy:

Foam cells (lipid-laden macrophages) - early lesion
Fibrous cap: SMCs + collagen + proteoglycans
Necrotic lipid core: Cholesterol crystals (needle-shaped clefts), debris, foam cells
Calcification (basophilic deposits)
Lymphocytes in adventitia
Cholesterol crystals (biconvex rhomboid clefts dissolved out during processing - empty spaces)

12. INFLAMMATORY BOWEL DISEASE (IBD)

CROHN'S DISEASE vs ULCERATIVE COLITIS

Feature	Crohn's Disease	Ulcerative Colitis
Location	Any part of GI tract (mouth to anus); most common terminal ileum + colon	Colon only (rectum always involved, extends proximally)
Distribution	Skip lesions (normal areas between affected segments)	Continuous/diffuse (no skip lesions)
Depth	Transmural (full thickness)	Mucosal + submucosal only
Wall thickness	Thickened ("rubber hose" consistency)	Thin
Mucosa	Cobblestone appearance	Granular, bloody mucosa
Ulcers	Deep, linear/knife-like fissures	Shallow, broad ulcers
Fistula/Fissure	Common (due to transmural)	Rare
Rectal involvement	Rectum often SPARED	Rectum ALWAYS involved
Granulomas	Sarcoid-like NON-caseating granulomas (40-60%)	Absent
Malignancy risk	Low	HIGH (cancer risk increases with duration)
Gross	Cobblestoning, skip lesions, creeping fat (mesenteric fat wrapping around bowel)	Pseudopolyps (islands of inflamed mucosa), continuous ulceration

Etiology (Both): Genetic (NOD2 mutation - Crohn's), abnormal gut microbiome, dysregulated immune response, smoking (Crohn's worse; UC better), environment

Pathogenesis: Dysregulated mucosal immunity → Th1/Th17 response (Crohn's) or Th2 (UC) → Cytokine cascade (TNF-α, IL-6, IL-23) → Mucosal inflammation and destruction

Microscopy - Crohn's:

Transmural inflammation
Non-caseating granulomas (40-60%)
Fissures extending through wall
Lymphoid aggregates throughout bowel wall

Microscopy - UC:

Mucosal/submucosal inflammation only
Crypt abscesses (neutrophils filling crypts) - characteristic
Goblet cell depletion
Mucosal ulceration
Pseudopolyps (regenerating mucosa)
Dysplasia in longstanding disease

13. EMPHYSEMA

Definition: Permanent abnormal enlargement of the airspaces distal to the terminal bronchiole, accompanied by destruction of alveolar walls, WITHOUT significant fibrosis.

Etiology:

Cigarette smoking (most common) - causes centriacinar emphysema
Alpha-1 antitrypsin deficiency (A1AT) - causes panacinar emphysema
Age (senile emphysema)

Pathogenesis - Protease-Antiprotease Imbalance:

Smoking → Neutrophil/macrophage influx → Release of elastase (destroys elastin) + MMP (destroys collagen) → Antiproteases overwhelmed (A1AT normally inhibits elastase) → Alveolar wall destruction → Air trapping

Types:

Type	Location of Destruction	Cause
Centriacinar (most common)	Proximal acinus (respiratory bronchioles)	Smoking
Panacinar	Entire acinus	A1AT deficiency
Paraseptal	Distal acinus (subpleural)	Can cause spontaneous pneumothorax
Irregular	Adjacent to scars	Scarring/post-inflammatory

Gross:

Enlarged, hyperinflated lungs (barrel chest)
Pale, voluminous
Lungs don't collapse when chest opened
Large bullae (>1 cm air spaces) visible on surface (especially in A1AT deficiency)

Microscopy:

Enlarged airspaces with destruction of alveolar walls
Loss of alveolar septa (septa appear as floating wisps)
Thin, attenuated walls
No significant inflammation or fibrosis (unlike UIP)
Loss of pulmonary capillary bed (contributes to cor pulmonale)

14. PYELONEPHRITIS

Definition: Suppurative (pus-forming) inflammation of the kidney and renal pelvis due to bacterial infection, involving the parenchyma, tubules, and interstitium.

Etiology:

E. coli (most common - 85%) - due to P-fimbriae adhesin
Proteus, Klebsiella, Enterococcus, Staphylococcus
Risk factors: Female sex, urinary obstruction, urinary catheter, pregnancy, diabetes, vesicoureteric reflux

Pathogenesis:

Ascending route (most common): Bacteria from fecal flora colonize perineum → urethra → bladder → ureter → kidney (facilitated by VUR in children)
Hematogenous (descending): Bacteremia → kidneys (less common; Staphylococcus)

ACUTE PYELONEPHRITIS:

Gross:

Enlarged kidney
Abscesses: Small, yellow, raised streaks/wedge-shaped foci extending from medulla to cortex
Purulent exudate in pelvis
Hyperemic (red) cortex

Microscopy:

Suppurative inflammation - neutrophils in tubular lumina and interstitium
Tubular necrosis with PMN casts
Glomeruli and vessels relatively spared (early)
Focal abscesses

CHRONIC PYELONEPHRITIS:

Gross:

Asymmetric, irregular coarse scarring (unlike diffuse fine scarring in glomerulonephritis)
Broad U-shaped cortical scars overlying dilated, clubbed calyces
Contracted, shrunken kidney

Microscopy:

Thyroidization (most characteristic): Tubules filled with pink homogeneous casts resembling thyroid colloid
Interstitial fibrosis
Glomerulosclerosis
Lymphocytic interstitial infiltrate
Periglomerular fibrosis

15. NEPHRITIC vs NEPHROTIC SYNDROME

Feature	Nephritic	Nephrotic
Proteinuria	Mild (<3.5 g/day)	Massive (>3.5 g/day)
Hematuria	Yes (RBC casts)	No (or minimal)
Edema	Mild-moderate	Massive, periorbital, pitting
Hypertension	Yes (fluid retention)	Yes
Hypoalbuminemia	No/mild	Severe
Hyperlipidemia	No	Yes
Mechanism	Inflammatory destruction of GBM	Loss of charge/size barrier → protein leak
Examples	Post-strep GN, IgA nephropathy, RPGN	MCD, Membranous, FSGS, Diabetic nephropathy

Post-Streptococcal GN (Classic Nephritic):

2-3 weeks after strep throat/skin infection
Mechanism: Type III hypersensitivity (immune complex deposition)
Gross: Enlarged, flea-bitten kidney (petechiae on surface)
Microscopy: Diffuse hypercellular glomeruli (endothelial + mesangial proliferation); sub-epithelial humps (immunoglobulin deposits); neutrophil infiltrate; "humps" on EM
IF: Granular IgG + C3 ("starry sky" pattern)

16. INFECTIVE ENDOCARDITIS

Definition: Infection of the endocardium, typically involving the heart valves, characterized by vegetations (masses of fibrin, platelets, and microorganisms on valve surfaces).

Etiology:

Acute IE: Staphylococcus aureus (most virulent, attacks normal valves)
Subacute IE (SBE): Streptococcus viridans (less virulent, attacks damaged valves)
Risk factors: Rheumatic heart disease, congenital heart disease, IV drug users, prosthetic valves, dental procedures

Pathogenesis:

Endothelial damage (turbulence, rheumatic disease) → Platelet + fibrin thrombus (sterile vegetation) → Bacteremia → Bacteria seed the thrombus → Infected vegetation forms → Valve destruction + emboli

Gross:

Acute IE: Large, bulky, destructive vegetations; valve leaflet perforation; abscess formation
Subacute IE: Smaller vegetations; less destructive
Vegetations on mitral valve (most common) then aortic valve
IV drug users: Tricuspid valve (right-sided)

Microscopy:

Vegetations: Fibrin + platelets + bacteria + inflammatory cells
Underlying valve: Necrosis, ulceration, inflammatory infiltrate
Acute: Acute suppurative inflammation, abscess
Subacute: Granulation tissue + chronic inflammation at base of vegetation

Clinical signs:

Osler's nodes (painful tender nodules on fingers/toes)
Janeway lesions (painless hemorrhagic spots on palms/soles)
Roth's spots (retinal hemorrhages)
Splinter hemorrhages (nail beds)

17. PYOGENIC vs TUBERCULAR OSTEOMYELITIS

Feature	Pyogenic Osteomyelitis	Tubercular Osteomyelitis
Organism	Staph. aureus (most common), Salmonella (sickle cell)	Mycobacterium tuberculosis (from lung via hematogenous)
Age	Children (hematogenous)	Any age
Location	Metaphysis of long bones (rich blood supply)	Spine (Pott's disease - vertebral TB), ends of long bones
Inflammation	Suppurative (pus-forming)	Granulomatous (caseating)
Sequestrum	Yes (dead bone surrounded by pus)	Rare
Involucrum	Yes (new bone around sequestrum)	Less common
Draining sinus	Pyogenic draining sinus	"Cold abscess" (no heat/redness - chronic, no acute signs)
Gross (Pyogenic)	Bone destruction, pus, periosteal elevation, sequestrum + involucrum	Caseous necrosis, caries sicca (dry/dry necrosis), cold abscess, gibbus deformity (spine)
Microscopy	Suppurative - neutrophils, abscess, bone destruction, reactive new bone	Caseating granuloma, Langhans giant cells, epithelioid cells

18. GLOMERULONEPHRITIS

Definition: Bilateral, inflammatory disease of the glomeruli, usually immunologically mediated.

Mechanisms:

Immune complex deposition (Type III HSR) - most common
Anti-GBM antibodies (Type II HSR) - Goodpasture's disease
Pauci-immune (ANCA-associated)

Quick Summary Table:

Type	LM	EM	IF	Syndrome
Post-strep GN	Hypercellular glomeruli, PMNs	Subepithelial humps	Granular IgG+C3	Nephritic
IgA Nephropathy (Berger's)	Mesangial expansion	Mesangial deposits	IgA dominant	Nephritic (hematuria)
Goodpasture's	Crescents	Subendothelial deposits	Linear IgG+C3	Nephritic/RPGN
Minimal Change	Normal	Foot process fusion	Negative	Nephrotic
Membranous	Spike and dome	Subepithelial deposits	Granular IgG+C3	Nephrotic
MPGN	Tram-track GBM, lobular	Subendothelial + mesangial	C3 ± IgG	Mixed

19. PEPTIC ULCER

Definition: A mucosal defect (ulcer) extending through the muscularis mucosa into submucosa or deeper, occurring in areas exposed to acid-pepsin.

Etiology:

H. pylori infection (70-90% of duodenal ulcers; 65-75% of gastric ulcers) - most important
NSAIDs (inhibit PGs → reduce mucus/bicarbonate → mucosal damage)
Stress ulcers (Curling's ulcer - burns; Cushing's ulcer - head injury)
Zollinger-Ellison syndrome (gastrinoma → massive acid secretion)

Pathogenesis:

H. pylori → Urease → NH3 → Neutralizes acid around bacteria → Survival → Releases toxins (VacA, CagA) → Disrupts mucosal barrier → Gastritis → Ulcer

Gastric vs Duodenal Ulcer:

Feature	Gastric Ulcer	Duodenal Ulcer
Acid secretion	Normal/Low	HIGH
H. pylori	Yes (65-75%)	Yes (90%)
Malignant potential	Small risk of cancer	Almost never malignant
Pain	Eating WORSENS pain	Eating RELIEVES pain
Location	Lesser curvature (most common)	First part of duodenum (anterior wall)

Gross:

Round/oval punched-out ulcer with CLEAN edges
Perpendicular (vertical) walls
Smooth, flat base (due to granulation tissue)
Surrounding mucosa folds radiate toward ulcer (contrast with malignant ulcer: raised everted edges, necrotic base)

Microscopy (4 zones from surface to depth):

Necrotic zone (top) - fibrinous exudate + necrotic debris
Inflammatory exudate zone - neutrophils
Granulation tissue zone - vessels + fibroblasts
Fibrous scar zone (base) - dense collagen

20. GASTRIC vs DUODENAL ULCER (COMPARISON)

(Covered in point 19 above - see comparison table)

21. PROSTATE CARCINOMA - GRADING + GLEASON GRADING

Definition: Adenocarcinoma arising from prostatic acinar cells (posterior zone predominantly).

Etiology:

Most common cancer in men (>65 years)
Risk factors: Age, Black race, family history, BRCA2 mutations, high-fat diet, testosterone

Pathogenesis:

Androgen receptor signaling → Prostate epithelial cell proliferation → PTEN loss, ETS gene fusion (TMPRSS2-ERG) → Carcinoma development

Gross:

Firm, gritty, gray-white nodular mass
Posterior zone of prostate (peripheral zone)
Early: Not visible grossly; detected by biopsy
Advanced: Hard, stony prostate on PR exam; spread to seminal vesicles, bladder, rectum

Microscopy:

Small glands, closely packed, back-to-back (no intervening stroma)
Single cell lining (loss of basal cell layer - important diagnostic feature)
Prominent nucleoli
Intraluminal crystalloids (eosinophilic)
Perineural invasion (diagnostic of malignancy)

GLEASON GRADING SYSTEM:

Based on glandular architecture (not cytology)
Grade 1-5 assigned to the two most common patterns (primary + secondary)
Gleason Score = Primary grade + Secondary grade (range 2-10)

Gleason Score	Prognosis	Features
2-6 (low)	Good	Well-formed glands, closely packed
7	Intermediate	Poorly formed glands
8-10 (high)	Poor	No gland formation, solid sheets/cords

Grade 1: Uniform, round, well-separated glands
Grade 3 (most common): Infiltrating separate glands, variable size
Grade 4: Fused/ill-defined glands, cribriform pattern
Grade 5: No gland formation, single cells, solid sheets

Tumor marker: PSA (Prostate Specific Antigen) - elevated in carcinoma, BPH, prostatitis

22. WILMS' TUMOR (NEPHROBLASTOMA)

Definition: Malignant embryonal neoplasm of the kidney, recapitulating different stages of normal nephrogenesis (kidney development). Most common renal tumor of childhood.

Etiology:

Peak age: 3-4 years
WT1 gene mutation (Wilms tumor gene 1 - chromosome 11p13)
Associated syndromes:
- WAGR syndrome: Wilms tumor + Aniridia + Genitourinary anomalies + mental Retardation
- Beckwith-Wiedemann syndrome
- Denys-Drash syndrome

Pathogenesis:

WT1 gene (tumor suppressor) mutation → Failure of normal nephroblast differentiation → Persistent embryonal tissue → Nephrogenic rests → Wilms tumor

Gross:

Large, solitary, well-encapsulated renal mass
Soft, gray-white, fish-flesh cut surface
Hemorrhage, cysts, necrosis
Replaces most of kidney
Unilateral in 95%

Microscopy - CLASSIC TRIPHASIC PATTERN (PATHOGNOMONIC):

Blastemal component: Small, round, blue cells (primitive, undifferentiated - like small round blue cell tumor)
Epithelial component: Tubules and glomeruloid structures (attempted differentiation)
Stromal component: Spindle cells (mesenchyme-like)

All three components = classic Wilms' tumor (Triphasic)

Anaplasia (unfavorable histology): Nuclear enlargement, hyperchromasia, abnormal mitosis → Worse prognosis

23. CELIAC DISEASE (GLUTEN-SENSITIVE ENTEROPATHY)

Definition: Immune-mediated inflammatory disorder of the small intestine triggered by ingestion of gluten (gliadin fraction of wheat/barley/rye) in genetically susceptible individuals (HLA-DQ2/DQ8).

Etiology:

Gluten/gliadin exposure
Genetic: HLA-DQ2 (90%) or HLA-DQ8
Autoimmune: Anti-tissue transglutaminase (anti-tTG) antibodies

Pathogenesis:

Gliadin → Deamidated by tissue transglutaminase → Presented by HLA-DQ2/DQ8 on APCs → CD4 T-cell activation → Th1 cytokines (IFN-γ, TNF) → Villous atrophy + Crypt hyperplasia → Malabsorption

Gross:

Small intestine: Loss of visible mucosal folds (flattened, smooth mucosa)
Atrophic appearance

Microscopy - CLASSIC TRIAD:

Villous atrophy (short, blunted, or absent villi - reduced surface area)
Crypt hyperplasia (deep, elongated crypts - compensatory)
Intraepithelial lymphocytes (IELs) >30 per 100 epithelial cells - most sensitive finding

Lamina propria: Plasma cells, lymphocytes, eosinophils

Lab: Anti-tTG IgA (most sensitive), Anti-endomysial IgA, Anti-gliadin Ab; HLA typing

Responds to gluten-free diet → reversal of histology Complication: T-cell lymphoma of small intestine (enteropathy-associated T-cell lymphoma)

24. BRONCHIECTASIS

Definition: Permanent, irreversible dilation of the bronchi and bronchioles due to destruction of the bronchial wall components (muscle + elastic tissue), caused by recurrent/chronic infection and inflammation.

Etiology:

Post-infectious: TB, whooping cough (most common causes globally), measles
Cystic fibrosis (most common cause in developed countries)
Immunodeficiency (recurrent infections)
Bronchial obstruction (foreign body, tumor)
Congenital: Kartagener's syndrome (immotile cilia - situs inversus + sinusitis + bronchiectasis)

Pathogenesis:

Persistent infection → Inflammation → Neutrophil elastase/MMP release → Destruction of bronchial wall elastic tissue and muscle → Bronchial dilation → Pooling of secretions → More infection ("vicious cycle")

Gross:

Dilated bronchi extending to pleural surface (normally don't reach pleura)
Filled with purulent mucus
Types: Cylindrical, Varicose, Saccular (most severe) dilation
Lower lobes predominant (gravity-dependent pooling)

Microscopy:

Dilated bronchi with inflammatory exudate in lumen
Destruction of bronchial wall: Loss of cartilage, smooth muscle, elastic tissue
Ulceration of bronchial mucosa
Squamous metaplasia of epithelium
Peribronchial fibrosis
Lymphocytic inflammation in wall

25. ENDOMETRIAL HYPERPLASIA

Definition: Proliferation of endometrial glands with increased gland-to-stroma ratio (>1:1), caused by excess estrogenic stimulation.

Etiology:

Unopposed estrogen (no progesterone counterbalance)
Anovulatory cycles (PCOS), obesity (peripheral estrogen from fat), exogenous estrogen
Estrogen-secreting tumors (granulosa cell tumor of ovary)
Tamoxifen use (partial agonist at uterus)

Pathogenesis:

Excess estrogen → Continuous proliferative phase → Gland crowding → Hyperplasia → If PTEN mutation → Endometrial intraepithelial neoplasia (EIN) → Endometrioid carcinoma

Classification (WHO):

Simple hyperplasia without atypia - cystic glands, low malignant potential (1%)
Complex hyperplasia without atypia - crowded glands, low risk (3%)
Simple hyperplasia with atypia - cytologic atypia, moderate risk (8%)
Complex hyperplasia with atypia - crowded + atypical cells; 29% risk of carcinoma

Gross: Thickened, polypoid endometrium (>4 mm on ultrasound in post-menopausal women)

Microscopy:

Simple: Dilated (cystic) glands lined by columnar epithelium, normal stroma
Complex: Back-to-back glands ("gland-in-gland"), reduced stroma
Atypical: Round cells, prominent nucleoli, loss of polarity, increased N:C ratio

26. EWING'S SARCOMA

Definition: Malignant primitive neuroectodermal tumor (PNET) of bone, composed of uniform small round blue cells.

Etiology:

Peak age: 5-20 years (teenage boys most common)
2nd most common malignant bone tumor in children (after osteosarcoma)
t(11;22) translocation → EWSR1-FLI1 fusion gene - PATHOGNOMONIC

Location: Diaphysis (midshaft) of long bones (femur most common), flat bones (pelvis, ribs, scapula)

Pathogenesis:

EWSR1-FLI1 fusion → Abnormal transcription factor → Primitive mesenchymal cell transformation → Small round blue cell tumor

Gross:

Destructive, gray-white soft mass in diaphysis
Cortical destruction with periosteal elevation
Soft tissue extension
"Onion-skin" periosteal reaction (layers of reactive periosteum) - X-ray finding

Microscopy:

Small, round, blue cells (uniform, dark nuclei, scant cytoplasm)
Arranged in lobules/sheets
Homer-Wright pseudorosettes (cells arranged around central neurofibrillary core - in PNET component)
PAS positive (glycogen in cytoplasm - important diagnostic feature)
CD99 (MIC2) positive - immunohistochemistry
No osteoid formation (unlike osteosarcoma)

27. HEPATITIS B

Definition: Viral hepatitis caused by Hepatitis B virus (HBV), a DNA virus (Hepadnaviridae family), causing acute or chronic liver inflammation.

Etiology/Transmission:

Parenteral: Blood transfusion, needle sharing (IV drug use), needlestick injury
Sexual transmission (unprotected sex)
Vertical (perinatal): Mother to child (most common mode in endemic areas)
Hemodialysis patients, healthcare workers

Pathogenesis:

HBV infects hepatocytes → Cell-mediated immunity (CTLs) attack infected hepatocytes → Liver cell injury (NOT direct cytopathic; immune-mediated)
Chronic infection → Cirrhosis → Hepatocellular carcinoma (HCC)
HBsAg → If remains positive >6 months = Chronic carrier

HBV Markers:

Marker	Significance
HBsAg	Surface antigen; Present in infection + carriers
HBeAg	High infectivity, active viral replication
HBcAb (IgM)	Acute infection ("window period" marker)
HBcAb (IgG)	Past infection or chronic
HBsAb	Immunity (vaccination or recovery)
HBV DNA	Viral load

Gross:

Acute: Enlarged, yellow-green liver (jaundice); soft
Chronic/Cirrhosis: Shrunken, nodular, firm liver

Microscopy - ACUTE:

Hepatocyte swelling (ballooning degeneration)
Acidophil bodies (Councilman bodies) = apoptotic hepatocytes (rounded, eosinophilic)
Lobular disarray
Lymphocytic infiltration in portal tracts

Microscopy - CHRONIC:

Ground glass hepatocytes (HBsAg accumulation in SER - pale, homogeneous, pink cytoplasm) - PATHOGNOMONIC of HBV
Portal tract fibrosis
Interface hepatitis (piecemeal necrosis)
Cirrhosis (bridging fibrosis → regenerative nodules)

Orcein stain: Stains HBsAg in ground glass cells - brown color

28. ACUTE APPENDICITIS

Definition: Acute inflammation of the vermiform appendix, usually due to obstruction followed by bacterial infection.

Etiology:

Obstruction by fecalith (hardened feces) - most common in adults
Lymphoid hyperplasia - most common in children
Foreign body, worms (Oxyuris/Enterobius)

Pathogenesis:

Obstruction → Mucus secretion continues → Intraluminal pressure increases → Venous occlusion → Bacterial proliferation (E. coli, Bacteroides, others) → Inflammation → Neutrophil infiltration → Gangrene → Perforation → Peritonitis

Gross:

Early: Red, congested, swollen appendix; serosal surface dull
Acute suppurative: Enlarged, tense, red-purple; fibrinopurulent exudate on serosa
Gangrenous: Black-green discoloration; about to perforate
Perforated: Hole visible, fecal peritonitis

Microscopy:

Neutrophil infiltration of the muscularis propria - DIAGNOSTIC (minimal diagnostic criterion)
Congestion of submucosal vessels
Ulceration of mucosa
Edema of wall
Fibrinopurulent periappendicitis on serosa
Gangrenous appendicitis: Transmural necrosis, hemorrhage, bacteria in wall

29. COPD (CHRONIC OBSTRUCTIVE PULMONARY DISEASE)

Definition: Preventable and treatable lung disease characterized by persistent airflow limitation that is not fully reversible, associated with chronic inflammation of the airways and lung parenchyma. Includes Chronic Bronchitis + Emphysema.

Etiology:

Smoking (most important cause - 90% of cases)
Air pollution, occupational dust, biomass fuel
Genetic: Alpha-1 antitrypsin deficiency (emphysema component)

Chronic Bronchitis (Clinical Definition):

Productive cough for at least 3 months in 2 consecutive years
Mechanism: Smoking → Mucus hypersecretion → Infection → Chronic inflammation

Gross (Chronic Bronchitis):

Thickened, edematous bronchial walls
Mucus plugging
Enlarged airways, purulent secretions

Microscopy (Chronic Bronchitis):

Reid Index >0.5 (DIAGNOSTIC): Ratio of mucous gland thickness to bronchial wall thickness (normally <0.4; elevated due to mucous gland hypertrophy)
Goblet cell hyperplasia (in small airways)
Squamous metaplasia of bronchial epithelium
Chronic inflammatory infiltrate (lymphocytes, macrophages)
Smooth muscle hypertrophy

Emphysema: (See point 13 above)

Blue Bloater (Chronic Bronchitis): Obese, cyanotic, edematous, productive cough Pink Puffer (Emphysema): Thin, pursed lips breathing, hyperinflated chest, minimal cyanosis

30. TYPE I vs TYPE II DIABETES MELLITUS

Feature	Type I DM	Type II DM
Mechanism	Autoimmune destruction of beta cells	Insulin resistance + relative insulin deficiency
Onset	Childhood/young (<30 yrs)	Adults (>40 yrs), increasingly in obese young
Body habitus	Lean	Obese
Insulin levels	Absent/very low	Normal or high initially
Ketoacidosis	Common (DKA)	Rare (HONK = hyperosmolar state)
HLA association	HLA-DR3, DR4	No HLA association
Autoantibodies	Anti-islet, Anti-insulin, Anti-GAD	Absent
Beta cells	Destroyed	Decreased, amyloid deposition

Pancreatic Microscopy:

Type I: Insulitis (lymphocytic infiltration of islets), loss/absence of beta cells
Type II: Amyloid deposition in islets (islet amyloid polypeptide = IAPP), reduced beta cell mass

Complications of DM (same for both types):

Microvascular: Diabetic nephropathy, Diabetic retinopathy, Diabetic neuropathy
Macrovascular: MI, stroke, peripheral vascular disease
Others: Recurrent infections, cataracts, Charcot's joint

Diabetic Nephropathy (Microscopy):

Kimmelstiel-Wilson lesion (nodular glomerulosclerosis) - PATHOGNOMONIC of DM
Diffuse glomerulosclerosis (more common but less specific)
GBM thickening

31. RHEUMATIC FEVER + RHEUMATIC HEART DISEASE

Definition: Rheumatic fever is an acute, recurrent, immunologically mediated multisystem inflammatory disease occurring 2-4 weeks after Group A Streptococcal pharyngitis.

Etiology:

Group A beta-hemolytic Streptococcus (Strep. pyogenes) pharyngeal infection
Autoimmune (molecular mimicry): Streptococcal M-protein antigens mimic cardiac proteins

Pathogenesis:

Strep pharyngitis → Antibodies form against M-protein → Cross-react with cardiac antigens (sarcolemmal proteins, tropomyosin) → Type II + IV HSR → Carditis, arthritis, chorea

Jones Criteria (Diagnosis):

Major: Carditis, Migratory polyarthritis, Sydenham's chorea, Erythema marginatum, Subcutaneous nodules
Minor: Fever, elevated ESR/CRP, prolonged PR interval, previous RF

ASCHOFF BODY (PATHOGNOMONIC of RF):

Focal collection of inflammatory cells around central area of fibrinoid necrosis
Aschoff cells (Caterpillar/Owl-eye cells): Large macrophage-derived cells with distinctive nuclei
- "Caterpillar" (Anitschkow cells): Ribbon-like chromatin in owl-eye arrangement
Surrounded by lymphocytes + plasma cells
Located in myocardium (interstitial) - myocarditis

Gross (Rheumatic Heart Disease - Chronic):

Mitral stenosis (most common valve lesion in RHD)
"Fish mouth"/"Buttonhole" deformity of mitral valve (stenotic orifice)
Thickened, fused, calcified valve leaflets
Fusion of commissures
Leaflets shortened, rigid; chordae tendineae fused + shortened

Microscopy:

Aschoff bodies in myocardium (acute phase)
Fibrous thickening of valve leaflets
Neovascularization of valve (new capillaries)
Calcification (chronic)
Vegetations on valve closure line (small, warty, 1-2mm - on ATRIAL surface of mitral valve)

32. PORTAL HYPERTENSION

Definition: Sustained elevation of portal venous pressure above 12 mmHg (normal: 5-10 mmHg), due to obstruction to blood flow through the portal system.

Etiology:

Pre-hepatic	Intra-hepatic (Most common)	Post-hepatic
Portal vein thrombosis	Cirrhosis (most common cause overall)	Budd-Chiari syndrome
Splenic vein thrombosis	Schistosomiasis, sarcoidosis	Right heart failure
AV fistula	Primary biliary cirrhosis	Constrictive pericarditis

Pathogenesis:

Obstruction → Portal pressure rises → Portosystemic collateral vessels open → Varices → Complications

Consequences:

Consequence	Site	Significance
Esophageal varices	Esophagus	Rupture → Massive fatal hematemesis
Hemorrhoids	Rectum (anorectal varices)	Bleeding PR
Caput medusae	Paraumbilical veins (superficial abdominal wall)	Cosmetic + sign
Splenomegaly	Spleen	Hypersplenism → Pancytopenia
Ascites	Peritoneum	Discomfort, SBP, respiratory compromise

Gross (Liver in Cirrhosis): Shrunken, nodular, firm, tough liver; micronodular (<3mm - alcoholic) vs macronodular (>3mm - viral)

Microscopy (Cirrhosis):

Regenerative nodules surrounded by fibrous septa (bridging fibrosis)
Loss of normal lobular architecture
Fatty change, hepatocyte necrosis, inflammation
Reticulin stain highlights fibrosis; Masson's Trichrome stains collagen blue

33. SALIVARY GLAND TUMORS

Definition: Tumors arising from the major (parotid, submandibular, sublingual) or minor salivary glands.

Classification:

Tumor	Gland	Benign/Malignant	Key Feature
Pleomorphic Adenoma (mixed tumor)	Parotid (most common salivary gland tumor)	Benign	Most common salivary tumor overall
Warthin's Tumor (cystadenolymphoma)	Parotid (bilateral 10%)	Benign	Associated with smoking; in older males
Mucoepidermoid Carcinoma	Parotid	Malignant (most common malignant)	Mucous + epidermoid + intermediate cells
Adenoid Cystic Carcinoma	Minor salivary glands (palate)	Malignant	Perineural invasion; cribriform pattern

Pleomorphic Adenoma:

Etiology: Most common salivary gland tumor; parotid gland; 4th-6th decade; PLAG1 gene rearrangement

Gross: Well-encapsulated, lobulated, firm, gray-white; "rubbery" texture; mobile

Microscopy:

"Pleomorphic" = Two-component tumor:
- Epithelial component: Duct-like structures (inner luminal cells)
- Myoepithelial component: Outer myoepithelial cells
Mesenchymal/stromal component: Chondroid (cartilage-like), myxoid, osteoid areas - MIXED/PLEOMORPHIC
No atypia in benign form
Incomplete encapsulation → recurrence if inadequate excision

34. ASTHMA

Definition: Chronic inflammatory disorder of the airways characterized by airway hyper-responsiveness, episodic, reversible bronchoconstriction, and chronic inflammation.

Etiology:

Extrinsic (Allergic) - 70%	Intrinsic (Non-allergic) - 30%
Type I HSR (IgE-mediated)	Non-immune triggers
Allergens: pollens, dust mites, animal dander	Aspirin, cold air, exercise, infections
Atopic individuals	Non-atopic
Childhood onset	Adult onset

Pathogenesis:

Early phase (minutes): Allergen → IgE on mast cells → Mast cell degranulation → Histamine + LTC4/D4/E4 + Prostaglandins → Bronchoconstriction + Mucus secretion + Vasodilation

Late phase (4-8 hrs): Eosinophil + T-cell recruitment → Cytokines (IL-4, IL-5, IL-13) → Sustained inflammation → Airway remodeling

Gross:

Lungs hyperinflated, don't fully deflate
Mucus plugs throughout airways
Thickened bronchial walls

Microscopy:

Curschmann spirals (whorled mucus plugs in airways)
Charcot-Leyden crystals (crystallized eosinophil proteins - diamond-shaped)
Eosinophilic infiltration of airway wall - HALLMARK
Thickened basement membrane (subepithelial fibrosis)
Smooth muscle hypertrophy
Mucous gland hyperplasia
Goblet cell hyperplasia

35. DIABETIC NEPHROPATHY

Definition: Kidney disease secondary to diabetes mellitus, the most common cause of end-stage renal disease (ESRD) worldwide.

Etiology: Chronic hyperglycemia in DM Type I or II

Pathogenesis:

Hyperglycemia → Non-enzymatic glycosylation of GBM proteins → GBM thickening → Loss of anionic charge → Proteinuria
Hyperfiltration → Glomerular hypertrophy → Eventually scarring
AGE (Advanced Glycation End-products) → Mesangial expansion

Gross:

Early: Enlarged kidneys (hyperfiltration)
Late: Shrunken, scarred (sclerosis)
Waxy cortex

Microscopy:

Diffuse glomerulosclerosis: Diffuse increase in mesangial matrix (most common)
Nodular glomerulosclerosis (Kimmelstiel-Wilson lesion): Ovoid/spherical hyaline nodules in peripheral mesangium - PATHOGNOMONIC
GBM thickening
"Capsular drop" lesion (hyaline deposit between Bowman's capsule and parietal epithelium)
"Fibrin cap" lesion (hyaline on glomerular capillary wall)
Arteriolosclerosis (hyaline arteriosclerosis) - affects BOTH afferent AND efferent arterioles (unique to DM)

36. ANEURYSM

Definition: Localized abnormal dilation of a blood vessel (or heart chamber) involving all 3 layers of the vessel wall (true aneurysm) or only adventitia/surrounding tissue (false/pseudoaneurysm).

Types:

Type	Description	Cause
True aneurysm	All 3 layers dilate	Atherosclerosis, syphilis, Marfan's
False (Pseudo) aneurysm	Breach in wall; hematoma contained by adventitia/perivascular tissue	Trauma, post-MI free wall rupture
Dissecting aneurysm	Blood splits into media	Hypertension, Marfan's (cystic medial necrosis)

Common Types:

Abdominal Aortic Aneurysm (AAA): Below renal arteries; >3 cm; Atherosclerosis; Risk of rupture (>5 cm)
Berry (Saccular) Aneurysm: Circle of Willis; Congenital; Rupture → Subarachnoid hemorrhage
Mycotic Aneurysm: Infected vessel wall (from bacteremia, IE)
Syphilitic Aneurysm: Ascending aorta; Obliterative endarteritis of vasa vasorum → Media ischemia

Gross:

Saccular (berry-shaped, local bulge) or Fusiform (spindle-shaped, diffuse)
May contain laminated thrombus
Atherosclerotic plaque in wall

Microscopy:

Thinning + fibrosis of media
Loss of elastic fibers (elastin breakdown)
Atherosclerosis of intima
Cystic medial necrosis (Marfan's): Loss of smooth muscle cells + elastic fibers in media; filled with mucoid material ("cystic" spaces)

37. FIBROADENOMA (BREAST)

Definition: Most common benign tumor of the female breast, composed of both epithelial (glandular) and stromal (fibrous) components.

Etiology:

Young women (15-35 years)
Estrogen-sensitive (may enlarge in pregnancy)
Lobular origin

Gross:

Well-encapsulated, mobile, rubbery, firm nodule
"Breast mouse" (moves freely on palpation)
Gray-white, whorled cut surface
1-3 cm usually

Microscopy:

Two patterns (intracanalicular vs pericanalicular):
- Intracanalicular: Stroma compresses ducts into slit-like spaces ("antler-horn" pattern)
- Pericanalicular: Stroma surrounds open, round ducts
Benign epithelial cells lining glands (no atypia)
Abundant fibrous stroma
No mitoses

38. CARCINOMA BREAST

Definition: Malignant neoplasm arising from the ductal or lobular epithelium of the breast.

Etiology:

BRCA1 (chromosome 17q) + BRCA2 (chromosome 13q) mutations - hereditary (5-10%)
Female sex, age, family history, early menarche, late menopause, nulliparity, obesity
HER2/neu amplification, hormone receptor status

Types:

Invasive Ductal Carcinoma (IDC) - NOS: Most common (75%) - no special features
Invasive Lobular Carcinoma (ILC): 10%; Single-file ("Indian file") pattern; bilateral
Ductal Carcinoma In Situ (DCIS): Pre-invasive; Comedo type has central necrosis
Lobular CIS (LCIS): Marker of risk; not treated as cancer

Gross:

Hard, gritty, gray-white mass
Irregular, stellate (star-shaped) outline (due to fibrotic reaction)
Poorly defined borders
Skin dimpling (ligament of Cooper involvement)
Nipple retraction

Microscopy:

IDC: Irregular nests/cords/sheets of carcinoma cells in desmoplastic stroma; nuclear pleomorphism + mitoses
ILC: Single-file arrangement (Indian file), targetoid pattern around ducts; small cells
DCIS: Ductal structures filled with carcinoma cells, BM intact; Comedo type has central necrosis + calcification

Grading (Nottingham/Bloom-Richardson Grade): Based on:

Tubule formation
Nuclear pleomorphism
Mitotic count (Grade 1 = well; Grade 3 = poorly differentiated)

39. BENIGN PROSTATIC HYPERPLASIA (BPH)

Definition: Non-malignant enlargement of the prostate gland due to hyperplasia of both stromal (smooth muscle/fibroblastic) and epithelial (glandular) components.

Etiology:

Age-related (>50 years; present in 90% men >80 years)
Androgens (DHT - Dihydrotestosterone) - main driver (5-alpha reductase converts testosterone → DHT)
Estrogen may sensitize tissue to DHT

Location: Periurethral zone (central/transition zone) - compresses urethra (Contrast: Prostate carcinoma = peripheral/posterior zone)

Gross:

Enlarged prostate (normal: 20g; BPH: 60-100g+)
Multiple firm, rubbery nodules in central zone
Cut surface: White-yellow nodules + cystic spaces

Microscopy:

Stromal hyperplasia: Increased fibromuscular stroma
Glandular hyperplasia: Large irregular glands lined by two cell layers (inner columnar + outer basal)
Papillary infoldings into gland lumina
Corpora amylacea (concentric, calcified, laminated bodies in gland lumina) - characteristic but not specific

40. AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE (ADPKD)

Definition: Most common hereditary renal disease, causing progressive bilateral renal cyst formation leading to renal failure.

Etiology:

ADPKD1: PKD1 gene (chromosome 16) - encodes Polycystin-1 (85% of cases; more severe)
ADPKD2: PKD2 gene (chromosome 4) - encodes Polycystin-2 (15% of cases; milder)
Autosomal dominant inheritance (50% chance per child)

Pathogenesis:

Mutant polycystin → Abnormal ciliary signaling in renal tubular cells → Tubular cell proliferation + fluid secretion → Cyst formation and growth → Compression of normal parenchyma → Renal failure

Gross:

Massively enlarged bilateral kidneys (can weigh >4 kg each!)
Replaced by innumerable cysts of varying sizes
Normal kidney architecture destroyed
Cysts contain clear serous or hemorrhagic fluid

Microscopy:

Large cysts lined by flat to cuboidal epithelium
Intervening compressed normal renal parenchyma
Fibrosis in areas of compressed tissue

Associated extrarenal manifestations:

Liver cysts (most common extrarenal - 30%)
Berry aneurysms (intracranial - rupture = subarachnoid hemorrhage)
Mitral valve prolapse
Pancreatic cysts

41. ADULT RESPIRATORY DISTRESS SYNDROME (ARDS)

Definition: Life-threatening form of acute respiratory failure resulting from diffuse alveolar damage (DAD), characterized by severe hypoxemia, non-cardiogenic pulmonary edema, and bilateral infiltrates.

Etiology:

Direct (pulmonary) injury: Pneumonia, aspiration, inhalation of toxic gases, drowning
Indirect (systemic) injury: Sepsis (most common cause overall), major trauma, burns, DIC, pancreatitis, massive transfusion

Pathogenesis:

Injury to alveolar epithelium (type I pneumocytes) + capillary endothelium → Increased permeability → Protein-rich fluid floods alveoli → Surfactant destroyed → Alveolar collapse → Hypoxemia → Cytokine storm perpetuates damage

Stages:

Exudative phase (Day 1-7): DAD with edema + inflammation
Proliferative phase (Day 7-21): Type II pneumocyte proliferation (repair attempt)
Fibrotic phase (>21 days): Fibrosis replaces damaged tissue

Gross:

Heavy, wet, red-purple lungs ("liver-like")
No airspace visible
No foam (non-cardiogenic)

Microscopy (DAD - Hallmarks):

Hyaline membranes (pink, glassy membranes lining alveolar ducts - PATHOGNOMONIC of ARDS)
Intra-alveolar edema + fibrin
Type I pneumocyte necrosis
Type II pneumocyte hyperplasia (repair phase - cuboidal cells replace normal flat type I)
Interstitial inflammation

42. GLIAL TUMORS OF CNS

Definition: Tumors arising from glial cells (astrocytes, oligodendrocytes, ependymal cells) of the central nervous system.

WHO Classification (2021):

Tumor	Grade	Key Feature
Diffuse Astrocytoma (IDH mutant)	II	Slow-growing, IDH mutation
Anaplastic Astrocytoma (IDH mutant)	III	Increased mitoses
Glioblastoma (GBM) (IDH wild-type)	IV	Most malignant brain tumor; Adults
Oligodendroglioma (IDH mutant, 1p/19q co-deletion)	II/III	"Fried egg" cells
Ependymoma	II/III	Perivascular pseudorosettes
Pilocytic Astrocytoma	I (most benign)	Children, cerebellum; BRAF V600E

Glioblastoma (GBM) - Most Important:

Gross:

Butterfly glioma (crosses corpus callosum)
Variegated appearance: Gray-white + areas of hemorrhage (red) + yellow necrosis
Infiltrative, no defined border

Microscopy:

Pseudopalisading necrosis (tumor cells lining up around necrotic areas) - PATHOGNOMONIC
Glomeruloid microvascular proliferation (new vessel formation)
High cellularity, pleomorphism, abundant mitoses
Serpiginous necrosis

Oligodendroglioma:

"Fried egg" cells = Round nuclei with clear cytoplasm (artifact of fixation)
Chicken-wire vasculature (delicate branching capillaries)
Calcifications (psammoma-like)
IDH mutation + 1p/19q deletion = better prognosis + chemoradiant sensitive

43. ASCHOFF BODIES + CARDIAC LESIONS (RHEUMATIC FEVER)

(Covered in detail in Point 31 - Rheumatic Fever)

Quick Summary of Cardiac Lesions in RF:

Phase	Lesion	Location
Pericarditis	Fibrinous "bread-and-butter" pericarditis	Pericardium
Myocarditis	Aschoff bodies	Myocardium (interstitial)
Endocarditis	Verrucous vegetations (1-2mm, warty) on valve closure line	Mitral valve (atrial surface)
Chronic	Fish-mouth/buttonhole mitral stenosis	Mitral valve

Aschoff Body Components:

Central fibrinoid necrosis
Surrounding Anitschkow cells (caterpillar cells) - pathognomonic
Lymphocytes + plasma cells
Aschoff giant cells (multinucleate macrophages)

44. PYOGENIC vs TUBERCULAR MENINGITIS

Feature	Pyogenic (Bacterial) Meningitis	Tubercular Meningitis
Organisms	N. meningitidis, Strep. pneumoniae, E. coli (neonates), H. influenzae	Mycobacterium tuberculosis
Exudate	Purulent (pus) in subarachnoid space	Gelatinous/fibrinous
Location	Subarachnoid space → especially basal + convexities	Basal meningitis (especially basal cisterns)
CSF - cells	PMNs (neutrophils) dominant	Lymphocytes dominant
CSF - glucose	Very LOW (<40 mg/dL)	Low
CSF - protein	HIGH	High
CSF - opening pressure	HIGH	High
Gross	Yellow-green pus on meningeal surface; "exudate fills sulci"	Gelatinous exudate at base of brain; miliary granules
Microscopy	Suppurative - neutrophils in subarachnoid	Granulomatous - caseating granulomas, Langhans giant cells
Complications	Waterhouse-Friderichsen syndrome (N. meningitidis), brain abscess	Hydrocephalus (most common), cranial nerve palsies, arteritis

45. DM → COMPLICATIONS

(Covered in Point 30 - diabetic complications)

Quick visual summary:

DIABETES → 
├── MICROVASCULAR
│   ├── Nephropathy → Kimmelstiel-Wilson lesions → ESRD
│   ├── Retinopathy → Cotton-wool spots → Neovascularization → Blindness
│   └── Neuropathy → Peripheral + Autonomic neuropathy
├── MACROVASCULAR
│   ├── Atherosclerosis (accelerated) → MI, Stroke
│   └── Peripheral vascular disease → Diabetic foot + Gangrene
└── OTHERS
    ├── Infections (impaired immunity)
    ├── Cataracts + Glaucoma
    ├── Charcot's joint (neuropathic)
    └── Acanthosis nigricans (Type II DM)

46. HEPATOCELLULAR CARCINOMA (HCC)

Definition: Primary malignant tumor of hepatocytes; most common primary liver malignancy.

Etiology:

Hepatitis B + C (most common causes worldwide)
Cirrhosis (from any cause)
Aflatoxin B1 (from Aspergillus flavus in stored grains - especially in Africa/Asia)
Alcohol, NAFLD, Hemochromatosis, Wilson's disease
Tumor marker: AFP (Alpha-fetoprotein) elevated in 75%

Pathogenesis:

Chronic hepatocyte injury → Regeneration → Accumulation of mutations (TP53, CTNNB1/β-catenin, TERT) → HCC
HBV: HBx protein disrupts p53; integrates into genome

Gross:

Usually on background of cirrhosis
Solitary or multinodular mass
Yellow-green (bile-staining), soft, hemorrhagic
Vascular invasion common (portal vein thrombosis)

Microscopy:

Cells resemble hepatocytes (large polygonal cells, prominent nucleoli, abundant granular cytoplasm)
Trabecular (plate-like) pattern - most common
Bile production by tumor cells (diagnostic)
Mallory-Denk bodies may be present
Vascular invasion (distinguishes from benign adenoma)
CD10+, AFP+, HepPar-1+ (hepatocyte paraffin-1) on IHC

47. GASTRITIS

Definition: Inflammation of the gastric mucosa.

Types:

ACUTE GASTRITIS:

Etiology: NSAIDs (most common - reduce PGs), alcohol, stress, H. pylori (acute)
Gross: Congested, edematous mucosa; superficial erosions; hemorrhagic streaks
Microscopy: Neutrophilic infiltration of lamina propria + superficial epithelium; edema; mucosal erosion

CHRONIC GASTRITIS:

Type A (Autoimmune - rare, 10%):

Autoantibodies against parietal cells and intrinsic factor
Affects body/fundus → Loss of parietal cells → Achlorhydria → Pernicious anemia (B12 deficiency)
Gross: Atrophic, thinned gastric body mucosa
Microscopy: Loss of parietal + chief cells; lymphocytic/plasma cell infiltrate; intestinal metaplasia; enterochromaffin-like cell hyperplasia

Type B (H. pylori - common, 90%):

H. pylori infects antrum preferentially
Gross: Antral mucosa with thickened, nodular folds or erosions
Microscopy: Neutrophils in crypts (cryptitis - active gastritis), H. pylori organisms visible on surface (curved rods), lymphoid follicles (lymphoid follicles = hallmark of H. pylori chronic gastritis)
Giemsa/Warthin-Starry stain to identify H. pylori

48. GIANT CELL TUMOR OF BONE (GCT)

Definition: Locally aggressive, potentially malignant tumor of bone composed of proliferating mononuclear stromal cells and abundant osteoclast-like giant cells.

Etiology:

Young adults (20-40 years; after skeletal maturity)
Slightly more common in females
Most common site: Epiphysis of long bones (distal femur, proximal tibia, distal radius)
"Around the knee" most common

Pathogenesis:

Neoplastic stromal cells express RANKL → Recruit and activate osteoclast precursors → Osteoclast-like giant cells → Bone destruction
H3F3A mutations in stromal cells (p.Gly34Trp)

Gross:

Epiphyseal + metaphyseal lytic lesion extending to subchondral bone
"Soap bubble" appearance on X-ray (expansile, multiloculated)
Red-brown, soft, friable mass
Hemorrhage and cystic spaces
No clear margins (locally aggressive)

Microscopy:

Osteoclast-like giant cells (multinucleate, abundant cytoplasm, 50-100 nuclei/cell)
Mononuclear stromal cells (spindle-shaped; the neoplastic component!)
Evenly distributed giant cells throughout the stroma (not clustered around necrosis)
Hemosiderin deposits
No osteoid formation
Reactive bone at periphery

Key point: The giant cells are REACTIVE (they're just osteoclasts recruited by the neoplastic stromal cells)

QUICK STAIN REMINDER FOR SYSTEMIC PATHOLOGY

Stain	What to look for	Disease
ZN stain	Red AFB bacilli	TB
Giemsa / Warthin-Starry	H. pylori curved rods	Chronic gastritis
Oil Red O (frozen section)	Fat (red droplets)	Steatosis
PAS stain	Glycogen in Ewing's	Ewing's sarcoma
Orcein stain	Ground glass hepatocytes (brown)	Hepatitis B
Congo Red	Apple-green birefringence	Amyloid
Masson's Trichrome	Collagen (blue)	Cirrhosis, fibrosis
Reticulin	Loss of architecture	HCC vs adenoma, cirrhosis
Alcian blue	Goblet cells (blue)	Barrett's esophagus
Silver (Methenamine)	Spike + dome pattern	Membranous GN
Oil Red O	Lipid in foam cells	Atherosclerosis
Von Kossa	Calcium (black)	Dystrophic calcification
CD99/MIC2	Positive	Ewing's sarcoma
TTF-1	Positive	Adenocarcinoma lung
CD10, HepPar1	Positive	HCC

HISTOPATH DIAGRAMS TO REMEMBER (As noted in your image - ★ MUST)

These are the most commonly asked diagrams in practicals and theory:

Coagulative necrosis - ghost cells, anucleate
Granuloma with Langhans giant cell - horseshoe nuclei
Reed-Sternberg cell - owl-eye nucleolus
Auer rods in AML
Kimmelstiel-Wilson lesion - nodular mesangial deposits
Hyaline membrane in ARDS
Pseudopalisading necrosis in GBM
Triphasic Wilms' tumor
Psammoma bodies in ovarian serous tumor
Call-Exner bodies in granulosa cell tumor
Indian file arrangement in lobular carcinoma breast
Barrett's esophagus with goblet cells
Crypt abscess in UC
Non-caseating granuloma in Crohn's/Sarcoidosis
Ground glass hepatocytes in Hepatitis B
Fried egg cells in oligodendroglioma
Aschoff body in rheumatic fever
Thyroidization of tubules in chronic pyelonephritis

Exam Tip from your note: 5 marks = 8-9 points | 10 marks = 15 points | Histopath diagrams are a MUST ★

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