Gastrointestinal Tract Cytology

GIT Cytology: Basics - Scope & Smears

• Scope: Rapid diagnosis: neoplasia, inflammation, infections (H. pylori, CMV, Candida). Guides therapy.
• Specimen Types:
  • Exfoliative: Brushings (esophagus, stomach, bile duct), washings, ERCP-guided.
  • Aspiration: FNA (palpable/intraop), EUS-FNA (deep lesions: pancreas, LNs - gold standard).
• Smear Prep: Direct (quick), Cytospin (concentrates cells), Liquid-Based Cytology (LBC - uniform, less debris).
• Stains: Pap (nuclear detail), MGG/Diff-Quik (cytoplasmic, matrix), special (PAS-mucin, Grocott-fungi).

⭐ EUS-FNA offers high diagnostic yield (>85% sensitivity, >95% specificity) for solid pancreatic lesions.

Esophageal Cytology: Lesions - Gullet Gazing

• Normal Cells: Predominantly superficial squamous cells; few parabasal/intermediate.
• Benign Conditions:
  • Infections:
    • Candida: Pseudohyphae, budding yeasts. Inflammatory background.
    • HSV: 📌 3 'M's (Multinucleation, Molding, Margination), Cowdry type A inclusions.
    • CMV: Large cells with "owl's eye" intranuclear inclusions; granular cytoplasmic inclusions.
  • Reflux Esophagitis: Neutrophils, eosinophils, reactive squamous atypia, parakeratosis.
  • Barrett's Esophagus: Intestinal metaplasia: presence of goblet cells. Precursor to adenocarcinoma.

    ⭐ Goblet cells are the diagnostic hallmark of Barrett's esophagus, indicating intestinal metaplasia.

• Malignant Tumors:
  • Squamous Cell Carcinoma (SCC):
    • Cellular smears; pleomorphic squamous cells (single/clusters).
    • Irregular, hyperchromatic nuclei, ↑N/C ratio.
    • Keratinization (dense orangeophilic cytoplasm), "tadpole" or "fiber" cells. Tumor diathesis.
  • Adenocarcinoma (AdenoCa):
    • Glandular clusters, acini, or papillae.
    • Pleomorphic columnar cells, vacuolated cytoplasm, prominent nucleoli.
    • Signet ring cells may be present. Typically arises from Barrett's.

Gastric Cytology: Findings - Stomach Stories

• Normal Gastric Cells:
  • Superficial columnar: Honeycomb sheets, bland nuclei.
  • Deep glandular: Smaller, rounder, tight clusters.
• Inflammation & Reactive Changes:
  • Neutrophils, lymphocytes, plasma cells.
  • Nuclear enlargement, prominent nucleoli, reparative atypia.
  • Helicobacter pylori: Curved/S-shaped bacilli on mucus or epithelial surface.
• Intestinal Metaplasia:
  • Presence of goblet cells (key diagnostic feature).
  • +/- Brush border.
• Dysplasia (Pre-malignant):
  • ↑ N/C ratio, hyperchromasia, irregular nuclear membranes, pleomorphism.
  • Loss of cellular polarity, architectural disarray.
  • Graded: Low-grade (LGD) vs. High-grade (HGD).
• Gastric Adenocarcinoma:
  • Intestinal type: Glandular/acinar structures, pleomorphic cells, dirty necrotic background.
  • Diffuse type (Signet-ring cell carcinoma): Discohesive cells, large intracytoplasmic mucin vacuole pushing nucleus to periphery.
• MALT Lymphoma:
  • Monotonous population of small to medium-sized atypical lymphocytes.
  • Lymphoepithelial lesions (infiltrating glands).

⭐ > Signet-ring cells in gastric cytology, with their eccentric nucleus and mucin-filled cytoplasm, are a hallmark of diffuse-type gastric adenocarcinoma, often associated with linitis plastica.

Pancreato-Biliary Cytology: FNA & Brushings - Deep Dive Diagnostics

• Sampling: Endoscopic Ultrasound-guided FNA (EUS-FNA) for pancreas; Endoscopic Retrograde Cholangiopancreatography (ERCP)-brushings/FNA for biliary tree.
• Pancreatic Ductal Adenocarcinoma (PDAC):
  • Cellular smears: 3D clusters, single malignant cells.
  • Nuclear atypia: Pleomorphism, irregular membranes, prominent nucleoli, hyperchromasia.
  • Often mucinous background.
  • 📌 Mnemonic: "Pancreatic Pleomorphism, Prominent nucleoli".
• Cholangiocarcinoma:
  • Atypical glandular cells: Sheets, clusters, or single cells.
  • Nuclear features: Crowding, hyperchromasia, irregular contours.
  • Often less cellular & pleomorphic than PDAC.
• Other Lesions:
  • Pancreatic Neuroendocrine Tumors (PNETs): Plasmacytoid cells, "salt-and-pepper" chromatin.
  • Cystic lesions (e.g., IPMN, MCN): Mucin, variable epithelial atypia.
• Challenges: Differentiating reactive atypia from low-grade malignancy.

⭐ KRAS mutations are detected in >90% of pancreatic ductal adenocarcinomas and can be assessed on cytology samples.

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High‑Yield Points - ⚡ Biggest Takeaways

• Barrett's esophagus: goblet cells confirm intestinal metaplasia in esophageal samples.
• H. pylori: identifiable in gastric cytology, linked to gastritis and ulcers.
• Gastric adenocarcinoma: features signet ring cells, high N:C ratio, nuclear atypia.
• Esophageal SCC: shows keratinization, pleomorphism, and orangeophilic cytoplasm.
• GISTs: spindle cells and CD117 (c-KIT) positivity are diagnostic hallmarks.
• NETs: "salt and pepper" chromatin; positive for synaptophysin & chromogranin.
• Viral cytopathy: CMV (owl's eye inclusions), HSV (multinucleation, molding).