A 54-year-old man has fatigue and abdominal discomfort. Examination shows massive splenomegaly without lymphadenopathy. CBC shows pancytopenia. Bone marrow aspiration yields a dry tap; trephine biopsy shows interstitial infiltrates of mononuclear cells with abundant cytoplasm and circumferential hair-like villous projections. Which finding best confirms the diagnosis?

• A Tartrate-resistant acid phosphatase positivity ✓
• B Nuclear cyclin D1 expression
• C Presence of the Philadelphia chromosome
• D Coexpression of surface CD10

Explanation

Hairy cell leukaemia presents in middle-aged men with splenomegaly, pancytopenia, dry tap, and hairy cells that classically show tartrate-resistant acid phosphatase (TRAP) activity; the disease is now defined by the BRAF V600E mutation. Cyclin D1 identifies mantle cell lymphoma, the Philadelphia chromosome defines chronic myeloid leukaemia, and CD10 marks germinal centre derived lymphomas such as follicular and Burkitt lymphoma.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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