Slide 4 - MD Pathology Histological Description & Diagnosis

Stain

LOW POWER (Scanner/4x) Features

• Section shows a polypoid fragment of endometrial tissue with a pedunculated or sessile architecture
• The overall tissue is composed of an irregular admixture of endometrial glands, fibrous stroma, and prominent blood vessels
• Altered gland-to-stroma ratio compared to normal cycling endometrium - stroma appears expanded and fibrous
• Glands are widely and irregularly distributed, varying markedly in size - some are cystically dilated while others are smaller and compressed
• The background stroma is dense, fibrous, and hypocellular - sharply contrasting with the loose, cellular stroma of normal endometrium
• A central fibrotic core with thick-walled blood vessels is visible

HIGH POWER (10x/40x) Features

Glandular Architecture

• Glands show variable shapes: round, ovoid, irregularly branching, and cystically dilated
• Some glands display intraluminal epithelial infoldings and papillary tufting (particularly in the larger dilated glands)
• No "back-to-back" crowding or cribriform architecture (ruling out hyperplasia/malignancy)
• Gland lumina contain pale eosinophilic secretory debris

Epithelial Cell Details

• Glands lined by a single layer of columnar to cuboidal epithelium (simple columnar)
• Nuclei are uniform, oval, basally placed - no significant stratification
• No nuclear atypia, pleomorphism, or prominent nucleoli
• No mitotic figures identified
• Cytoplasm is moderately eosinophilic; some glands show inactive/resting appearance (not corresponding to current cycle day) - this mismatch with surrounding endometrium is diagnostically important

Stromal Details

• Stroma is dense fibrous/collagenous with spindle-shaped fibroblasts
• Lacks the normal compact cellular spindle-cell endometrial stroma
• No decidualization of stromal cells
• Stroma does not respond normally to hormonal stimulation (functionally inert stroma - key diagnostic feature of endometrial polyp)

Vascular Features

• Prominent thick-walled, hyalinized blood vessels - both arterioles and medium-sized vessels - present within the fibrotic stroma
• Thick-walled vessels (often described as "thick-walled vessels with hyalinized walls") are a hallmark diagnostic feature of endometrial polyp
• Small thin-walled vessels and capillaries also present

KEY DIAGNOSTIC FEATURES (Summary for Viva)

DIAGNOSIS

Endometrial Polyp

Diagnostic Criteria (for MD exam):

1. Polypoid architecture - localized overgrowth within the endometrial cavity
2. Irregular glands - varying sizes including cystic dilatation; often show inactive or proliferative pattern out-of-phase with surrounding endometrium
3. Fibrous stroma - hypocellular, collagenous, does not respond to progesterone (unlike normal endometrial stroma)
4. Thick-walled blood vessels (most characteristic feature) - hyalinized walls distinguishing it from normal endometrium
5. Absence of significant cytological atypia (if present, consider atypical endometrial polyp or malignancy)

Differential Diagnoses to Know:

• Endometrial hyperplasia - crowded glands, cellular stroma, responds to hormones; no thick vessels
• Secretory endometrium - sawtooth glands with subnuclear vacuoles, stromal edema, spiral arterioles (not hyalinized)
• Endometrial carcinoma - back-to-back glands, nuclear atypia, mitoses, stromal invasion
• Adenomyosis - endometrial glands/stroma deep within myometrium, no polypoid projection

Clinical Correlation:

• Most common cause of abnormal uterine bleeding in perimenopausal women
• May be estrogen-driven (associated with tamoxifen use, obesity, polycystic ovary)
• Small malignant transformation risk (~1-3%), higher in postmenopausal women
• Treatment: hysteroscopic polypectomy

Exam tip (MD Pathology viva): The single most distinguishing feature of endometrial polyp from normal endometrium or hyperplasia is the thick-walled, hyalinized blood vessels within a fibrous stroma, combined with glands that are out-of-phase (non-responsive to hormonal cycling).

• The images are uploaded as IMG_3239, 3240, 3241, 3242, 3243, 3244, 3245, 3246
• The 4th image in the sequence = IMG_3242

🔬 SLIDE 4 — MD PATHOLOGY COMPLETE HISTOLOGICAL DESCRIPTION

STAIN

GROSS / SCANNER VIEW (Low Power - 4x)

• Section shows a polypoid fragment of endometrial tissue
• Irregular, variably-sized glands randomly distributed within an altered stroma
• Altered gland-to-stroma ratio - stroma appears expanded, fibrous, and distinctly different from adjacent normal endometrium
• Some glands show cystic dilatation, others show branching and budding
• A prominent central fibrotic core with thick-walled blood vessels is visible
• No surface epithelium disruption or necrosis

LOW POWER (4x - 10x) FEATURES

HIGH POWER (40x) FEATURES

A. Glandular Architecture

• Glands show highly variable shapes: round, ovoid, elongated, irregularly branching, and some show "antler-like" or stellate profiles
• Some glands show cystic dilatation with intraluminal epithelial infoldings
• Intraluminal papillary tufting visible in larger dilated glands
• No back-to-back crowding or cribriform pattern (rules out carcinoma)
• No gland fusion or stromal disappearance (rules out complex hyperplasia)

B. Epithelial Cell Details

• Glands lined by simple columnar to pseudostratified columnar epithelium
• Endometrioid type lining
• Epithelial appearance: largely inactive to proliferative - notably OUT OF PHASE with surrounding endometrium (this mismatch is a key diagnostic clue)

C. Nuclear Features

• Nuclei are oval to elongated, regularly spaced
• Basally to mid-cell located (perpendicular to basement membrane)
• Chromatin is finely dispersed - no hyperchromasia
• No significant nuclear atypia, pleomorphism, or prominent nucleoli
• No mitotic figures

D. Cytoplasmic Features

• Cytoplasm is moderately eosinophilic
• No subnuclear glycogen vacuoles (rules out secretory phase)
• No mucin secretion
• No squamous metaplasia visible in this field

E. Stromal Details (Most Diagnostic Feature)

• Stroma is dense, fibrous, and hypocellular - collagenous
• Lacks the normal compact spindle-cell endometrial stroma of cycling endometrium
• NO decidualization of stromal cells (unlike late secretory phase)
• Stroma does NOT respond to progesterone - it is functionally inert
• Contains scattered bland spindle-shaped fibroblasts in collagenous background
• Some areas show myxoid change

F. Vascular Features (Pathognomonic Finding)

• Prominent thick-walled blood vessels with hyalinized walls - most distinctive hallmark
• Both arterioles and medium-sized vessels within fibrotic stroma
• These thick-walled vessels do NOT resemble normal spiral arterioles
• Represent chronic, non-cycling vessels - central diagnostic feature

KEY DIFFERENTIATING FEATURES

DIAGNOSIS

✅ ENDOMETRIAL POLYP

DIAGNOSTIC CRITERIA (for Exam/Viva)

1. Irregular, variably-sized glands - often cystically dilated, showing inactive/proliferative lining that is OUT OF PHASE with surrounding endometrium
2. Fibrous, hypocellular stroma - dense collagenous, functionally inert (does not respond to hormonal changes unlike normal endometrial stroma)
3. Thick-walled, hyalinized blood vessels within the stroma - this is the MOST DISTINCTIVE and PATHOGNOMONIC feature

DIFFERENTIAL DIAGNOSIS (Viva Points)

CLINICAL CORRELATION

• Most common cause of abnormal uterine bleeding (AUB) in peri- and postmenopausal women
• Pathogenesis: Estrogen-driven focal overgrowth; associated with tamoxifen use, obesity, PCOS, hypertension
• Age: 40-60 years most common
• Presentation: Menorrhagia, intermenstrual bleeding, postmenopausal bleeding
• Investigation: Transvaginal ultrasound + Saline infusion sonography + Hysteroscopy
• Treatment: Hysteroscopic polypectomy (definitive)
• Malignant transformation risk: ~1-3% (higher in postmenopausal, larger polyps, associated atypia)
• On immunohistochemistry: PTEN mutation often seen; ER/PR receptor expression present but discordant with cycle phase

Key Exam Tip (MD Pathology Viva): The single most distinguishing histological feature of an Endometrial Polyp is the thick-walled hyalinized blood vessels within fibrous, functionally inert stroma, combined with glands that are out-of-phase with the rest of the endometrium. In the MCQ/viva, if you see "irregular glands + fibrous stroma + thick-walled vessels" - the answer is Endometrial Polyp.

🔬 SLIDE 4 — COMPLETE MD PATHOLOGY DESCRIPTION

Clinical History: 48-year-old female | Bilateral solid-cystic ovarian masses

STAIN

GROSS CORRELATION

• Bilateral solid-cystic ovarian masses in a perimenopausal woman
• Grossly: cyst walls with increased papillary projections inside the cyst cavity
• No bulky solid tumor mass or capsular fixation (which would suggest frank malignancy)

LOW POWER (4x) FEATURES

• Section shows complex papillary and cystic architecture
• Hierarchical branching papillae - large primary papillae giving rise to progressively smaller secondary and tertiary projections, projecting into cystic spaces
• Fibrovascular stromal cores are present supporting each papilla
• No solid sheets of tumor cells
• No areas of necrosis
• No destructive stromal invasion - epithelial-stromal interface is maintained with clear basement membrane

HIGH POWER (10x/40x) FEATURES

A. Papillary Architecture

• Hierarchically branching papillae with a central fibrovascular core in each
• Papillary projections show increasing complexity compared to benign serous cystadenoma
• Some detached epithelial cell clusters visible floating in cystic spaces (characteristic feature)
• Focal areas of micropapillary budding - small papillae without fibrovascular cores arising directly from epithelial surface

B. Epithelial Cell Details

C. Nuclear Features

• Nuclei are round to oval, relatively uniform
• Mild to moderate nuclear atypia - mild loss of polarity, some crowding
• Chromatin: finely granular, evenly distributed
• Nucleoli: small, not prominent
• Mitoses: Occasional/rare - increased compared to benign but not brisk
• No marked pleomorphism, no bizarre nuclei, no atypical mitoses

D. Stromal Features

• Fibrovascular cores: edematous to mildly fibrous
• NO destructive stromal invasion - the hallmark distinguishing this from carcinoma
• No desmoplastic stromal reaction
• No inflammatory infiltrate

E. Special Features

• Detached epithelial cell clusters in luminal spaces (characteristic of borderline)
• Psammoma bodies: not identified in this field (though associated with serous tumors)
• No necrosis
• Basement membrane intact between epithelium and stroma throughout

THE CRITICAL DIFFERENTIATING CRITERION

"Epithelial hyperplasia with pseudostratification and tufting + branching papillae + mild nuclear atypia + NO destructive stromal invasion"

DIAGNOSIS

✅ SEROUS BORDERLINE TUMOR OF THE OVARY

(Atypical Proliferative Serous Tumor - APST)

DIAGNOSTIC CRITERIA (Berek & Novak's Gynecology / Robbins Pathology)

• Berek & Novak's Gynecology, p. 2307: "Approximately 10% of all ovarian serous tumors fall into the category of a borderline tumor... The criteria for diagnosis include epithelial hyperplasia in the form of pseudostratification, tufting, cribriform and micropapillary architecture, mild nuclear atypia and mild increased mitotic activity, detached cell clusters, and absence of destructive stromal invasion."
• Robbins Pathology: "Serous borderline tumors exhibit increased complexity of the stromal papillae, stratification of the epithelium, and mild nuclear atypia, but invasion of the stroma is not seen."

CLINICAL CORRELATION - WHY BILATERAL?

• Bilaterality occurs in ~30% of serous borderline tumors (vs 20% benign, 66% carcinoma) - Robbins
• Patient is 48 years (perimenopausal) - peak age for borderline tumors
• 50% of serous borderline tumors occur before age 40, but a significant proportion present in the 4th-5th decade

DIFFERENTIAL DIAGNOSIS

PROGNOSIS & MANAGEMENT (Viva Points)

• 5-year survival: ~95% for stage I disease
• Up to 40% can have spread beyond the ovary at diagnosis - but this alone does NOT equal malignancy
• 10% may have invasive peritoneal implants (= low-grade serous carcinoma) → worse prognosis (~50% 5-year survival)
• Most peritoneal implants are non-invasive → do NOT worsen prognosis significantly
• Treatment: Fertility-sparing surgery (cystectomy/salpingo-oophorectomy) in young women; bilateral salpingo-oophorectomy + staging in perimenopausal women
• No benefit from chemotherapy for borderline tumors without invasive implants
• Recurrence: Can occur even decades later; mostly as borderline recurrences

MOLECULAR/IHC NOTES (for Advanced Viva)

• BRAF V600E and KRAS mutations - present in ~60-70% of serous borderline tumors
• This links them to low-grade serous carcinoma (NOT high-grade)
• High-grade serous carcinoma is a SEPARATE entity arising from STIC (Serous Tubal Intraepithelial Carcinoma) with TP53 mutations
• ER/PR - may be positive
• WT1, PAX8 - positive (confirming serous Mullerian origin)

Key Exam Summary: Slide 4 from a 48F with bilateral solid-cystic ovarian masses shows Serous Borderline Tumor (Atypical Proliferative Serous Tumor). The diagnostic hallmarks are: hierarchically branching papillae + pseudostratified serous epithelium with tufting + mild nuclear atypia + detached cell clusters + NO stromal invasion. It sits between benign cystadenoma and frank serous carcinoma in the biologic spectrum, with an excellent prognosis for stage I disease.

📋 MD PATHOLOGY SLIDE DISCUSSION

Slide 4 — Serous Borderline Tumor of the Ovary

🔴 SECTION 1: IDENTIFICATION & DESCRIPTION

• WHO 2020 Classification: ICD-O code 8442/1 (borderline/low malignant potential)
• It sits between benign serous cystadenoma and low-grade serous carcinoma on the biologic spectrum

1. Epithelial hyperplasia - pseudostratification, tufting, cribriform, and/or micropapillary architecture
2. Mild nuclear atypia and mildly increased mitotic activity
3. Detached epithelial cell clusters floating in cystic spaces
4. Absence of destructive stromal invasion - this is the DEFINING criterion separating it from carcinoma

• In SBT: epithelium proliferates on papillae but does NOT invade the stroma; basement membrane is intact
• In serous carcinoma: irregular, haphazard invasion of stroma with desmoplastic reaction
• This single feature determines the diagnosis, regardless of how complex the papillary architecture appears

• Hierarchically branching papillae - large primary papillae branch into smaller secondary and tertiary projections
• Each papilla has a central fibrovascular stromal core
• Surface lined by pseudostratified columnar epithelium 2-3 layers deep
• Epithelial tufting and budding from papillary surfaces
• Detached epithelial cell clusters floating freely in luminal spaces
• No back-to-back crowding or cribriform pattern

🔴 SECTION 2: CLINICAL DISCUSSION

• Bilaterality occurs in ~30% of serous borderline tumors (Robbins Pathology)
• Compared to: 20% in benign cystadenoma, 66% in serous carcinoma
• Bilaterality in SBT is related to its Mullerian origin and the shared hormonal milieu affecting both ovaries
• In this 48-year-old perimenopausal patient, bilaterality with solid-cystic morphology raises concern and mandates thorough sampling of both ovaries and peritoneal surfaces to exclude invasive foci

• Represent ~10% of all ovarian serous tumors
• 50% occur before age 40 (younger than serous carcinoma)
• Peak incidence: 3rd to 5th decade
• This patient at 48 years fits the upper end of the typical age range
• More common than low-grade serous carcinoma
• No strong association with BRCA1/2 mutations (unlike high-grade serous carcinoma)

• Pelvic/abdominal pain or discomfort
• Abdominal distension or palpable pelvic mass
• Bilateral solid-cystic adnexal masses on transvaginal ultrasound or CT scan
• CA-125 may be mildly to moderately elevated (but non-specific)
• Ascites may be present if peritoneal spread
• Many cases are incidental findings on imaging

• Up to 40% of serous borderline tumors may have spread beyond the ovary at diagnosis (Berek & Novak's)
• NO - this does NOT automatically mean carcinoma
• The diagnosis of SBT vs. serous carcinoma is based entirely on histological features of the primary tumor, NOT on stage
• Extraovarian spread may be in the form of:
  • Non-invasive peritoneal implants (majority, ~90%) - favorable prognosis
  • Invasive peritoneal implants (~10%) - these are reclassified as low-grade serous carcinoma, worse prognosis

🔴 SECTION 3: PATHOGENESIS & MOLECULAR BIOLOGY

• Includes: Low-grade serous carcinoma, borderline tumors, mucinous carcinoma, endometrioid carcinoma, clear cell carcinoma
• Arises from ovarian surface epithelium or inclusion cysts via stepwise progression
• KRAS, BRAF, PTEN, PIK3CA, ARID1A mutations
• Chromosomally stable

• Includes: High-grade serous carcinoma (most common), undifferentiated carcinoma, carcinosarcoma
• Arises from STIC in fallopian tube fimbriae
• TP53 mutation (virtually universal), BRCA1/2 germline/somatic mutations
• Highly chromosomally unstable
• Presents at advanced stage

• Psammoma bodies are concentric laminated calcifications formed by dystrophic calcification around necrotic cells or secretions
• They are seen in all types of serous ovarian tumors - benign, borderline, and malignant
• In this slide: not identified in the field examined
• They are NOT specific for malignancy - Robbins: "Concentric calcifications (psammoma bodies) are common in all types of serous tumors but are not specific for neoplasia"
• When abundant, psammoma bodies are more characteristic of papillary serous carcinoma
• Also seen in: papillary thyroid carcinoma, meningioma, papillary renal cell carcinoma

🔴 SECTION 4: ADVANCED PATHOLOGY

• Designated when the tumor shows an exuberant micropapillary architecture - small papillae WITHOUT fibrovascular cores arising directly from larger papillae ("Medusa head" pattern)
• Papillae have a non-hierarchical branching pattern lined by a monomorphous population of cells (Fig. 39-2, Berek & Novak's)
• Clinical significance: These tumors are more frequently:
  • Bilateral
  • Exophytic (growing on ovarian surface)
  • Higher stage at presentation
  • More likely to have invasive peritoneal implants
  • Considered by some to be a precursor to low-grade serous carcinoma

• Definition: Small foci of individual cells or cell clusters invading into the papillary stroma, measuring <3 mm or <10 mm² - below the threshold for carcinoma
• Occurs in a minority of SBTs
• Increased ~9-fold in pregnant women with SBT (Berek & Novak's)
• Associated with lymphovascular space invasion in the primary tumor
• Critically: Stromal microinvasion is NOT associated with an aggressive clinical course
• Management: Patients with stromal microinvasion should be managed the same way as those without it - no escalation of therapy needed

• Marked nuclear pleomorphism - 3-fold variation in nuclear size
• Numerous mitoses - >12 per 10 HPF
• Atypical mitotic figures
• Multinucleated giant cells
• Solid sheets of tumor cells effacing stroma
• Widespread stromal infiltration/effacement
• No hierarchical papillary architecture
• TP53 mutation (>96%)
• Associated with STIC in fallopian tube
• Far more aggressive - Stage III/IV at presentation in most cases

🔴 SECTION 5: PROGNOSIS & MANAGEMENT

• Important caveat: "5-year survival is NOT synonymous with cure" - SBTs can recur after many years, sometimes decades later
• Recurrences are usually as borderline tumors (not frank carcinoma)
• Late recurrences (>10 years) do occur

• For a 48-year-old perimenopausal woman (fertility no longer a concern):
  • Bilateral salpingo-oophorectomy (BSO) + hysterectomy
  • Complete surgical staging: peritoneal washings, omental biopsy, pelvic/para-aortic lymph node sampling, multiple peritoneal biopsies
  • Appendectomy (if mucinous component suspected)
• For younger women desiring fertility:
  • Unilateral salpingo-oophorectomy + thorough staging
  • Cystectomy alone (higher recurrence risk)
• NO role for adjuvant chemotherapy in SBT without invasive implants
• If invasive implants present → reclassify as low-grade serous carcinoma → platinum-taxane chemotherapy

• HGSOC IHC pattern: p53 mutant (either diffuse strong >75% OR complete null), p16 block positive, WT1 positive, high Ki-67

🔴 BONUS VIVA RAPID-FIRE

Pro tip for MD Pathology viva: Always lead with the KEY criterion - "The diagnosis of serous borderline tumor requires absence of destructive stromal invasion. Without this criterion being satisfied, no matter how complex the papillae are, you cannot call it borderline - it becomes carcinoma once invasion appears."

🔬 EMERGENCY APPENDECTOMY SPECIMEN

Complete MD Pathology Description — All 9 Slides

📋 SLIDE-BY-SLIDE IDENTIFICATION

🏥 COMPLETE HISTOLOGICAL DESCRIPTION

STAIN

LOW POWER (4x) SURVEY — Overall Impression

1. Mucosa - Colonic-type crypts lined by columnar epithelium with goblet cells (Slide 9/IMG_3255) - focal ulceration in advanced area
2. Submucosa - Loose connective tissue with lymphoid aggregates
3. Muscularis propria - Inner circular and outer longitudinal smooth muscle layers (Slides 1-3, 7-8)
4. Serosa + Mesoappendix - Adipose tissue with peritoneal covering (Slides 4, 6)

HIGH POWER DESCRIPTION — Layer by Layer

🔴 A. MUCOSA (Slide 9 - IMG_3255)

• Colonic-type crypts lined by tall columnar epithelium with goblet cells - regular, parallel arrangement
• Lamina propria contains the normal appendiceal lymphoid tissue (abundant MALT - Mucosa-Associated Lymphoid Tissue)
• In more severely affected areas: mucosal ulceration with sloughing of the superficial epithelium
• Fibrinopurulent exudate filling the lumen (Slide 5) - composed of neutrophils, fibrin strands, and cellular debris
• The crypt architecture at the mucosal surface in Slide 9 appears relatively preserved, suggesting this is a less-affected region sampled for comparison

🔴 B. MUSCULARIS PROPRIA (Slides 1, 2, 3, 7, 8 — IMG_3247, 3248, 3249, 3253, 3254)

• Smooth muscle bundles: Spindle-shaped cells with cigar-shaped blunt-ended nuclei, eosinophilic cytoplasm, arranged in interlacing fascicles
• THE DIAGNOSTIC CRITERION: Dense neutrophilic infiltration between and within smooth muscle bundles
• Neutrophils identified by: small size, multilobed (3-5 lobes) dark nuclei, scant cytoplasm
• Distribution: Transmural - neutrophils permeating between individual muscle fibers and between fascicles
• Interstitial edema: Clear, optically empty spaces separating muscle bundles - a sign of acute vascular permeability change
• Vascular congestion: Dilated capillaries and venules stuffed with red blood cells, visible in Slide 2
• Margination of neutrophils along vessel walls (early emigration pattern) - Slide 2

🔴 C. MESOAPPENDIX / PERIAPPENDICEAL FAT (Slides 4, 6 — IMG_3252, IMG_3250)

• Disrupted adipocyte membranes - cells lose their sharp, polygonal borders
• Foamy macrophages (lipophages) infiltrating - clearing released lipid
• Dense neutrophilic infiltrate permeating between fat lobules
• Vascular congestion + micro-hemorrhages - extravasated erythrocytes in interstitium
• Nuclear dust (karyorrhexis) - degenerating neutrophil remnants
• This constitutes acute periappendicitis / mesoappendicitis - inflammation has breached the muscularis propria and spread to surrounding structures

DIAGNOSIS

✅ ACUTE SUPPURATIVE APPENDICITIS WITH PERIAPPENDICITIS

Stage: Suppurative (Phlegmonous)

PATHOLOGICAL STAGING OF ACUTE APPENDICITIS

PATHOGENESIS (Current Surgical Therapy 14e)

1. Luminal obstruction → bacterial overgrowth + mucus accumulation
2. Increased intraluminal pressure → visceral afferent nerve stretch → periumbilical pain (early)
3. Venous congestion → arterial compromise → ischemia
4. Transmural inflammation → neutrophil infiltration of muscularis propria
5. Serosal involvement → parietal peritoneum irritation → pain migrates to RLQ (McBurney's point)
6. Gangrene → perforation → peritonitis/abscess

📚 MD PATHOLOGY DISCUSSION QUESTIONS & ANSWERS

🔴 SECTION 1: IDENTIFICATION & DIAGNOSIS

• Gold-standard histological criterion: Presence of neutrophils within the muscularis propria
• This single criterion distinguishes true acute appendicitis from:
  • Normal appendix (neutrophils only in lumen or mucosa)
  • Lymphoid hyperplasia (no muscle wall infiltration)
  • Resolving appendicitis (mixed infiltrate, fibrosis)

• Mucosa (colonic-type crypts, goblet cells, MALT) → IMG_3255 (Slide 9)
• Muscularis propria (interlacing smooth muscle, diagnostic layer) → IMG_3247, 3248, 3249, 3253, 3254
• Mesoappendix/periappendiceal fat (adipose tissue) → IMG_3250 (normal fat), IMG_3252 (inflamed fat)
• Lumen (fibrinopurulent exudate, ulcerated mucosa) → IMG_3251

• Small, round cells (8-10 µm)
• Multilobed nucleus (3-5 lobes connected by thin chromatin filaments) - also called polymorphonuclear leukocytes (PMNs)
• Pale pink/eosinophilic granular cytoplasm (primary granules contain myeloperoxidase, elastase; secondary granules contain lactoferrin)
• Lobation distinguishes them from lymphocytes (single round nucleus) and macrophages (kidney-shaped nucleus, more cytoplasm)
• Nuclear dust (karyorrhexis): Fragmented neutrophil nuclei in necrotic areas

• Periappendicitis: Extension of acute inflammation beyond the muscularis propria into the serosa and mesoappendix (periappendiceal adipose tissue)
• Demonstrated in IMG_3252 (Slide 4): neutrophils infiltrating periappendiceal fat + fat necrosis + vascular congestion + micro-hemorrhages
• Indicates the inflammatory process has become transmural and is spreading beyond the appendix wall
• Clinically corresponds to: serosal inflammation causing parietal peritoneal irritation → localized peritonitis / RLQ rebound tenderness

• Fibrinopurulent exudate = fibrin + neutrophils + cellular debris filling the appendiceal lumen
• Components:
  • Fibrin: Coagulation cascade activated by tissue injury and vascular leak
  • Neutrophils: Primary responders; emigrated from congested vessels
  • Cellular debris/pus: Dead neutrophils (pus cells), sloughed mucosal epithelium
• This is termed empyema appendicis when the lumen is completely filled with pus
• The presence of mucosal ulceration here indicates progression beyond the early catarrhal stage

🔴 SECTION 2: PATHOGENESIS

• Lymphoid hyperplasia (especially in children - most common in age 5-15)
• Parasitic infections (e.g., Enterobius vermicularis, Ascaris)
• Neoplasm (e.g., carcinoid tumor - most common appendiceal neoplasm)
• Foreign body

1. Obstruction of appendiceal lumen
2. Continued mucus secretion → increased intraluminal pressure
3. Venous and lymphatic obstruction → mucosal edema and congestion
4. Bacterial proliferation (E. coli, Bacteroides fragilis, Klebsiella, Streptococcus)
5. Mucosal breach → submucosal and muscular wall invasion by bacteria and neutrophils
6. Muscularis propria neutrophilic infiltration = diagnostic threshold
7. Arterial compromise → ischemia → gangrene → perforation

• Early pain (periumbilical): Caused by distension of the appendix stretching visceral afferent nerve fibers → visceral pain → poorly localized, periumbilical/central
• Later pain (RLQ / McBurney's point): As inflammation becomes transmural and reaches the serosa, it irritates the somatically innervated parietal peritoneum → well-localized, sharp RLQ pain
• This pain migration is the classic hallmark of acute appendicitis
• McBurney's point: 1/3 of the distance from the right ASIS to the umbilicus

• E. coli (most common)
• Bacteroides fragilis (most common anaerobe; especially in gangrenous/perforated cases)
• Klebsiella pneumoniae
• Streptococcus spp.
• Enterococcus
• Pseudomonas aeruginosa
• In gangrenous and perforated appendicitis: E. coli and Bacteroides spp. in the majority

🔴 SECTION 3: CLINICAL CORRELATION

• A negative (normal) appendectomy occurs when the removed appendix shows no histological evidence of acute appendicitis
• Histologically: neutrophils in mucosa only (reactive), OR lymphoid hyperplasia, OR completely normal mucosa and muscularis
• IMPORTANT: Neutrophils in the mucosa/submucosa alone are NOT sufficient for diagnosis - only muscularis propria infiltration counts
• Rate: Has declined significantly with CT imaging. Historically ~20%, now <5% with CT-guided selection
• False positive histology pitfall: Luminal mucous accumulation or fecal material can cause focal mucosal neutrophilia without true appendicitis

• Score ≥7: High probability, proceed to surgery
• Score 5-6: Equivocal, CT/ultrasound recommended
• Score <5: Low probability, observe

1. Gangrenous appendicitis - full-thickness necrosis
2. Perforation - free rupture → generalized peritonitis
3. Pericolic/appendiceal abscess - if omentum/bowel walls off the perforated area
4. Phlegmon - mass of inflamed tissue without discrete abscess
5. Pylephlebitis - septic thrombophlebitis of the portal vein (rare, serious)
6. Liver abscess (secondary to pylephlebitis)
7. Intestinal obstruction - from adhesions (late complication)

• Carcinoid tumor (Well-Differentiated Neuroendocrine Tumor) is the most common appendiceal neoplasm
• Most occur at the tip of the appendix
• Small carcinoids (<2 cm) are almost never malignant
• Can cause luminal obstruction → secondary acute appendicitis
• This is why appendiceal specimens should always be examined histologically for an underlying tumor
• Gross: Firm, yellow-tan nodule, usually at tip
• Histology: Nests and trabeculae of uniform cells with round nuclei, "salt and pepper" chromatin, scant cytoplasm
• IHC: Chromogranin A, synaptophysin, CD56 positive

🔴 RAPID FIRE VIVA

📝 SECTION: STUDIES SHOW — HISTOPATHOLOGY DESCRIPTIONS

CASE 1 — Serous Borderline Tumor of the Ovary

CASE 2 — Emergency Appendectomy

CASE 3 — Endometrial Polyp (Slide 4, prior session)

CASE 4 — Fibroadenoma of Breast (Two slides)

CASE 5 — Secretory Phase Endometrium

FORMAT TEMPLATE — For Any Slide

Studies show sections from [organ/specimen] revealing [architecture at low power]. The [specific layer/component] shows [key feature]. [Cellular details at high power]. [Special features — inflammation/atypia/invasion]. [Negative findings — what is absent].

Diagnosis: [Condition] — [WHO classification if applicable]

• "Studies show sections from..."
• "The muscularis propria demonstrates dense neutrophilic infiltration..."
• "No destructive stromal invasion is identified..."
• "Thick-walled hyalinized vessels are conspicuously present..."
• "The epithelium shows pseudostratification and tufting..."
• "Subnuclear vacuolation is noted consistent with early secretory change..."
• "These features are consistent with a diagnosis of..."

📖 THEORY DISCUSSION — MD PATHOLOGY

All Slides: Emergency Appendectomy + Gynaecological & Breast Pathology

TOPIC 1: ACUTE APPENDICITIS

1.1 Anatomy of the Appendix

• Mucosa: Colonic-type crypts + abundant MALT (Mucosa-Associated Lymphoid Tissue) - the appendix is sometimes called the "intestinal tonsil"
• Submucosa: Loose connective tissue, lymphoid follicles often extending here
• Muscularis propria: Inner circular + outer longitudinal smooth muscle
• Serosa/Mesoappendix: Peritoneal covering + periappendiceal adipose tissue

1.2 Aetiology and Pathogenesis

• E. coli (most common)
• Bacteroides fragilis (predominant in gangrenous/perforated cases)
• Klebsiella pneumoniae, Streptococcus, Enterococcus, Pseudomonas aeruginosa

1.3 Pathological Stages — Morphology

Your slides represent predominantly Stage 2 (Suppurative) with periappendicitis (serosal extension)

1.4 The Gold Standard Histological Criterion

"The presence of neutrophil polymorphs within the muscularis propria"

• Neutrophils in the lumen alone = luminal contents contamination, not diagnostic
• Neutrophils in the mucosa alone = reactive change, may be seen in non-appendicitis conditions
• Neutrophils in the muscularis propria = TRUE acute appendicitis — irreversible inflammatory process

1.5 Periappendicitis

• Extension of acute inflammation through the full thickness of the appendiceal wall into the mesoappendix and serosa
• Histologically: neutrophilic infiltration of periappendiceal adipose tissue + fat necrosis + vascular congestion + micro-haemorrhages
• Clinical significance: The inflamed serosa makes contact with and irritates the somatically innervated parietal peritoneum → this is what causes the classic migration of pain to McBurney's point (RLQ)

1.6 Clinical Features

1. Periumbilical/central pain (visceral) → vague, colicky, poorly localised
2. Anorexia + nausea/vomiting (after pain onset - important diagnostic sequence)
3. Pain migrates to RLQ at McBurney's point (somatic, sharp, well-localised)
4. Fever (low-grade initially; high fever = perforation/gangrene)
5. Leukocytosis with neutrophilia

• McBurney's sign: Tenderness at McBurney's point
• Rovsing's sign: LLQ palpation causes RLQ pain (sensitivity 30-68%, specificity 58-91%)
• Psoas sign: RLQ pain on right hip extension (retrocaecal appendix) - sensitivity 16-39%
• Obturator sign: RLQ pain on internal rotation of right hip (pelvic appendix) - sensitivity 21-34%
• Guarding and rebound tenderness: Peritoneal involvement

1.7 Complications of Untreated Appendicitis

1. Gangrenous appendicitis - vascular thrombosis, full-thickness necrosis
2. Perforation - free rupture, faecal peritonitis
3. Localised appendiceal abscess - omentum/bowel walls off the site
4. Phlegmon - inflammatory mass without liquefaction
5. Generalised peritonitis - if walling-off fails
6. Pylephlebitis - septic portal vein thrombophlebitis (rare, grave)
7. Liver abscess - haematogenous spread via portal vein
8. Intestinal obstruction - late adhesion formation

1.8 Important Entities in Differential of Appendicitis

TOPIC 2: SEROUS BORDERLINE TUMOUR OF THE OVARY

2.1 WHO Classification of Ovarian Tumours (Robbins & Cotran)

1. Surface epithelium/fallopian tube epithelium → Epithelial-stromal tumours (most common - 65-70%)
2. Germ cells → Germ cell tumours
3. Sex cord-stromal cells → Sex cord-stromal tumours

2.2 Pathogenesis of Serous Tumours (Robbins & Cotran)

• Nulliparity (more ovulatory cycles = more epithelial disruption/repair)
• Family history of ovarian/breast cancer
• BRCA1/BRCA2 germline mutations
  • BRCA1 mutations in ~5% of patients <70 years with ovarian cancer
  • Estimated lifetime risk of ovarian cancer: 20-60% with BRCA1/BRCA2 mutations
• Protective factors: Oral contraceptives (suppress ovulation), tubal ligation, multiparity

2.3 Morphology of Serous Tumours (Robbins & Cotran)

• Borderline tumours: increased papillary projections within cysts, may grow on ovarian surface
• Malignant: large bulky solid-cystic mass, capsular nodularity and fixation

2.4 Psammoma Bodies — Theory

• Definition: Concentrically laminated calcifications formed by dystrophic calcification around necrotic cells
• Seen in: All types of serous ovarian tumours (benign, borderline, malignant)
• Also seen in: Papillary thyroid carcinoma, Meningioma, Papillary renal cell carcinoma
• NOT specific for malignancy - Robbins: "Psammoma bodies are common in all serous tumours but are not specific for neoplasia"
• Mechanism: Ca²⁺ deposition around dead tumour cells in papillary tips

2.5 Prognosis (Robbins & Cotran)

Borderline tumours may recur after many years — 5-year survival is NOT synonymous with cure

TOPIC 3: ENDOMETRIAL POLYP

3.1 Definition and Epidemiology

• Most common in perimenopausal women (40-50 years)
• Often presents with abnormal uterine bleeding (AUB) - inter-menstrual, post-menopausal, or menorrhagia
• Prevalence: 7-35% of women undergoing evaluation for AUB

3.2 Pathogenesis

• Driven by unopposed oestrogen stimulation → focal overgrowth of endometrium
• Associated with:
  • Obesity (peripheral aromatisation of androgens → oestrogen)
  • Tamoxifen use (paradoxical oestrogenic effect on endometrium)
  • Hypertension, diabetes
  • Polycystic ovarian syndrome (PCOS)
• The polyp stroma becomes fibrotic and oestrogen-insensitive over time → glands go out of phase with surrounding endometrium

3.3 Histological Features — Three Pathognomonic Criteria

1. Irregular variably-sized glands — cystically dilated, architecturally disorganised, out-of-phase (proliferative glands in secretory endometrium or vice versa)
2. Dense fibrous hypocellular stroma — functionally inert, does not respond to progesterone (unlike normal cycling stroma)
3. Thick-walled hyalinised blood vessels — pathognomonic finding; irregular, ectatic vessels with hyaline thickening of walls

3.4 Malignant Transformation

• Risk of malignancy in endometrial polyps: <1-5% (generally low)
• Higher risk if:
  • Post-menopausal women
  • Symptomatic (bleeding)
  • Polyp >1.5 cm
  • Tamoxifen-associated polyps (higher risk of endometrial carcinoma)
• Malignancy arising: Usually endometrioid adenocarcinoma or serous carcinoma within the polyp

TOPIC 4: FIBROADENOMA OF BREAST

4.1 Definition and Epidemiology

• Peak age: 15-35 years (young women) — responds to oestrogen
• Accounts for ~75% of all breast biopsies in women <30 years
• Usually solitary, but can be multiple (20%)
• Increases in size during pregnancy/lactation, regresses after menopause

4.2 Pathogenesis

• Oestrogen-dependent benign proliferation of both epithelial and stromal elements
• Driven by increased stromal sensitivity to oestrogen
• PTEN, MED12 mutations reported in some cases
• NOT considered a premalignant lesion in most cases

4.3 Gross Pathology

• Well-circumscribed, rubbery, firm, mobile ("breast mouse")
• Grey-white cut surface with whorled appearance
• Sharp borders — easily shelled out from surrounding breast tissue
• Size: usually 1-3 cm (can grow larger as "giant fibroadenoma" >5 cm)

4.4 Histological Patterns

• Bilayered duct epithelium: Inner luminal epithelial cells + outer myoepithelial layer (confirms benign)
• No nuclear atypia, no mitoses in epithelium
• Stroma: bland spindle cells, loose to myxoid, no pleomorphism

4.5 Important Differential — Phyllodes Tumour

4.6 Risk of Malignancy in Fibroadenoma

• Standard fibroadenoma: NO increased risk of breast cancer
• Complex fibroadenoma (with sclerosing adenosis, cysts >3mm, papillary apocrine change, epithelial calcification): 1.5-2× increased risk
• Fibroadenoma with adjacent proliferative disease + family history: ~3× increased risk

TOPIC 5: SECRETORY ENDOMETRIUM (Slide 2)

5.1 Normal Endometrial Cycle — Theory

Your slide (Slide 2/IMG_3240) shows early secretory phase Day 17-18: Subnuclear vacuoles with nuclei pushed toward lumen — the EARLIEST definitive sign of ovulation/progesterone response

5.2 Clinical Use of Endometrial Dating

• Endometrial dating was historically used to assess luteal phase adequacy and ovulatory status in infertility workup
• A discrepancy of >2 days between expected and actual histological date = "out-of-phase endometrium" (suggests luteal phase defect)
• Now largely replaced by progesterone assays but histology remains confirmatory

📊 INTEGRATED SUMMARY TABLE — ALL SLIDES

KEY EXAM THEORY POINTS TO MEMORISE

Acute Appendicitis: Gold standard = neutrophils in muscularis propria. Most common cause = fecalith. Most common organism = E. coli. Pain migration: visceral (periumbilical) → somatic (McBurney's) when serosa involved.

Serous Borderline Tumour: 10% of serous tumours. Hierarchical papillae + pseudostratification + NO invasion. BRAF/KRAS mutations. 30% bilateral. 5-year survival ~100% (stage I), NOT synonymous with cure.

Endometrial Polyp: Unopposed oestrogen. Triad: irregular glands + fibrous stroma + thick-walled hyalinised vessels. <5% malignant risk.

Fibroadenoma: Most common breast tumour in young women. Oestrogen-dependent. Biphasic. Pericanalicular + intracanalicular patterns. Bilayered epithelium confirms benign. NOT premalignant.

Secretory Endometrium: Subnuclear vacuoles = Day 16-17. First and most reliable sign of ovulation/progesterone effect.