Bone marrow aspiration in a 58-year-old man with massive splenomegaly yields a dry tap. Trephine biopsy shows interstitial infiltrates of medium-sized cells with abundant pale cytoplasm and a fried egg appearance, accompanied by marked reticulin fibrosis. Which cytochemical finding supports the diagnosis?
- A Myeloperoxidase block positivity
- B Tartrate-resistant acid phosphatase positivity ✓
- C Periodic acid-Schiff block positivity
- D Nonspecific esterase positivity inhibited by sodium fluoride
Correct answer: B. Tartrate-resistant acid phosphatase positivity
Explanation
Hairy cell leukemia presents in middle-aged men with splenomegaly, pancytopenia, a dry tap due to reticulin fibrosis, and fried egg appearing hairy cells. The neoplastic cells characteristically show tartrate-resistant acid phosphatase (TRAP) positivity and express CD11c, CD25, CD103, and annexin B1. Myeloperoxidase positivity is seen in myeloid blasts, PAS block positivity is classic for erythroleukemia blasts, and fluoride-inhibitable nonspecific esterase marks monocytic differentiation, none of which fit hairy cell leukemia.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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