Microscopy of a solid ovarian tumour in a 21-year-old woman shows sheets of uniform round cells with clear cytoplasm and central nuclei, scattered mature lymphocytes, and non-caseating granulomas. Immunohistochemistry is most likely positive for:
- A Inhibin and calretinin
- B CD99 and FLI-1
- C PLAP and OCT4 ✓
- D CK7 and PAX8
Correct answer: C. PLAP and OCT4
Explanation
This is dysgerminoma, the female counterpart of testicular seminoma. The primitive germ cells are immunoreactive for PLAP, OCT4, and CD117, and the lymphocytic infiltrate with sarcoid-like granulomas is a classic diagnostic clue. Inhibin and calretinin mark sex cord-stromal tumours, CK7 and PAX8 mark epithelial tumours, and CD99 with FLI-1 suggests Ewing sarcoma, a differential for small round blue cell ovarian tumours.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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