Appendiceal Pathology

Acute Appendicitis - Inflamed & Irate

• Etiology: Luminal obstruction. Common causes: fecalith (adults), lymphoid hyperplasia (children), carcinoid, parasites.
• Pathogenesis Flow:

• Clinical Features:
  • Pain: Periumbilical (visceral) → RIF (somatic, McBurney's point).
  • Systemic: Anorexia, Nausea/Vomiting, low-grade Fever.
  • Signs: Localized RIF tenderness, Rebound tenderness, Guarding. Special signs: Rovsing's, Psoas, Obturator.
• Diagnosis:
  • Alvarado Score (📌 MANTRELS) aids: Score ≥7 high probability.
    • (M:Migration, A:Anorexia, N:N/V, T:Tenderness RIF, R:Rebound, E:↑Temp(>37.3°C), L:Leukocytosis(>10,000/μL), S:Shift to left(>75%))
  • Labs: ↑WBC (neutrophilic leukocytosis), ↑CRP.
  • Imaging: USG (appendix >6mm diameter, non-compressible, wall thickening, target sign); CT (most accurate: fat stranding, complications).
• Pathology (Gross & Micro):
  • Gross: Swollen, erythematous, dull serosa; fibrinopurulent exudate.
  • Micro:

    ⭐ Neutrophilic infiltration of the muscularis propria is the pathognomonic histological hallmark.

    • Edema, vascular congestion, mucosal ulceration, transmural inflammation and necrosis.
• Complications: Perforation, peritonitis (localized/generalized), appendiceal abscess/phlegmon, pylephlebitis.

Appendiceal Neoplasms - Sneaky Surprises

• Often incidental; may mimic appendicitis or present as mass/PMP.
• Neuroendocrine Tumors (NETs/Carcinoids)
  • Most common; often at appendix tip.
  • Size critical: <1cm excellent prognosis; <2cm & no mesoappendiceal invasion usually benign course.
  • Markers: Chromogranin A, Synaptophysin.
• Mucinous Neoplasms
  • Spectrum: LAMN → HAMN → Mucinous Adenocarcinoma.
  • Low-Grade Appendiceal Mucinous Neoplasm (LAMN):
    • Bland cells, pushing border; risk of Pseudomyxoma Peritonei (PMP) if ruptured.
  • High-Grade Appendiceal Mucinous Neoplasm (HAMN): More atypical cells, higher risk.
  • Mucinous Adenocarcinoma: Invasive, desmoplastic, poorer prognosis.
• Goblet Cell Adenocarcinoma (GCA)
  • Aggressive; mixed glandular & neuroendocrine features. 📌 "Goblet cells gone rogue: a dangerous duo."
• Pseudomyxoma Peritonei (PMP)
  • "Jelly belly" from mucinous ascites, often due to ruptured appendiceal mucinous neoplasm (esp. LAMN).
• Non-Mucinous Adenocarcinoma
  • Colonic-type adenocarcinoma; generally poorer prognosis than NETs.

⭐ Appendiceal NETs <2cm without mesoappendiceal invasion are often cured by appendectomy alone.

Mucocele & Other Lesions - Appendix Oddities

• Mucocele: Grossly dilated appendix, mucin-filled.
  • Types:
    • Simple Mucocele: Obstruction (e.g., fecalith).
    • Mucinous Hyperplasia: No atypia.
    • Mucinous Cystadenoma: Benign, low-grade atypia.
    • Mucinous Cystadenocarcinoma: Malignant, invasive.
  • Risk: Rupture → Pseudomyxoma Peritonei (PMP) - gelatinous peritoneal material.

    ⭐ PMP: Gelatinous ascites from ruptured appendiceal mucinous neoplasms (LAMN/cystadenocarcinoma).

• Neuroendocrine Tumors (NETs/Carcinoids):
  • Most common appendiceal tumor, often at tip.
  • Often incidental. Good prognosis if < 2 cm, non-angioinvasive, no meso-extension.
  • Markers: Chromogranin A, Synaptophysin.
• Adenocarcinoma:
  • Rare, aggressive, colonic type.
• Lymphoma:
  • Rare, usually Non-Hodgkin Lymphoma (NHL).
• Diverticulosis/Diverticulitis:
  • Acquired outpouchings; inflammation can mimic appendicitis.

High‑Yield Points - ⚡ Biggest Takeaways

• Acute appendicitis, the most common cause of acute surgical abdomen, is typically due to luminal obstruction (e.g., fecalith, lymphoid hyperplasia).
• Key signs include periumbilical pain migrating to the RIF (Right Iliac Fossa) and McBurney's point tenderness.
• Major complications are perforation, leading to peritonitis, and appendiceal abscess formation.
• Neuroendocrine tumors (NETs/Carcinoids) are the most common appendiceal neoplasms, usually found incidentally at the tip.
• Appendiceal mucocele (dilatation by mucin) can be benign or malignant; rupture of a mucinous neoplasm can cause pseudomyxoma peritonei (PMP).