A 15-year-old boy has a pineal region mass. Biopsy shows large cells with clear cytoplasm and a prominent lymphocytic infiltrate. Which immunohistochemical marker is most likely positive?
- A PLAP ✓
- B GFAP
- C Synaptophysin
- D S-100
Correct answer: A. PLAP
Explanation
The histology is classic for germinoma. Germinomas are positive for placental alkaline phosphatase (PLAP), OCT3/4, and CD117. GFAP marks glial tumors, synaptophysin marks neuronal tumors, and S-100 is seen in schwannomas and melanomas. The lymphocytic infiltrate is a characteristic feature.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.