Gastrointestinal Biopsy – Short surgical Mock Diagnostic Challenge
Clinical Scenario:
A middle-aged individual with prolonged watery diarrhea and weight loss undergoes endoscopic biopsy of the appendix and small intestine.
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CORRECT ANSWER
Histopathological Description (Morphology)
Section shows structure of the appendix with hypertrophy of lymphoid follicles and lamina propria showing prominence of eosinophilic infiltrates. Muscularis propria is attenuated and serosa shows mild congestion. Also seen are 2-3 micron basophilic spherical structures attached to the surface of the mucosa. No malignancy seen in the section studied.
Remarks: Acid fast protozoal infection that causes severe watery diarrhea and treatment resistant in immunocompromised patients. Usually self limiting in immunocompetent.
Interpretation (Diagnosis)
Cryptosporidial infection (in correlation with the history).
Ancillary Tests / Remarks/ Further work up
Giemsa, GMS, Modified acid fast stain and PAS stain.
To check for immunocompromised status of the patient.
Stool examination for acid fast oocyst.
Differentials:
Cyclospora – larger (8–10 µm), autofluorescent
Microsporidia – smaller, intracytoplasmic
Giardia – free-floating in lumen
Quick Comparison Table
| Protozoan | Size | Stain | Intracellular Location | Unique Feature |
|---|---|---|---|---|
| Isospora | 25-30 μm | Acid-fast (+) | Intracellular | Large, oval oocysts |
| Cyclospora | 8-10 μm | Acid-fast (variable) | Intracellular | Double-walled oocysts |
| Crypto- sporidium | 4-6 μm | Acid-fast (+) | Intracellular but extra-cytoplasmic | Attaches to brush border |
| Microsporidia | 1-2 μm | Modified Trichrome (+) | Intra-cytoplasmic | Tiny spores in enterocytes |
Self-Assessment (Out of 5)
| Criteria | 0 | 0.5 | 1.0 | 1.5 |
|---|---|---|---|---|
| Morphological description | ||||
| Diagnostic interpretation | ||||
| Ancillary tests suggested |
Self assessment - score details
3.5 marks: Very good answer – correct diagnosis with most relevant details or insights
3.0 marks: Good answer – correct diagnosis with moderate detail (minor omissions) .
2.5 marks: Adequate answer (Pass) – core diagnosis is correct but answer is incomplete (e.g. missing some features or relying on ancillary tests to confirm) .
2.0 marks: Borderline answer – an incorrect or only partially correct diagnosis without a dangerous error (for example, misidentifying a specific entity but still recognizing benign vs. malignant) .
1.0–1.5 marks: Failing answer – a dangerously wrong diagnosis (major misinterpretation, such as calling a malignant process benign, or vice versa) or no meaningful answer at all
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