A 70-year-old man has progressive cytopenias, splenomegaly, and peripheral blood showing 'hairy' lymphocytes with flow cytometry positive for CD11c, CD25, CD103, and CD123. The BRAF V600E mutation is detected. What is the treatment of choice for this condition?
- A Fludarabine + cyclophosphamide + rituximab (FCR)
- B Cladribine (2-CdA) as a single agent ✓
- C Ibrutinib monotherapy
- D Chlorambucil + prednisolone
Correct answer: B. Cladribine (2-CdA) as a single agent
Explanation
The clinical and immunophenotypic features (CD11c, CD25, CD103, CD123 positivity) with BRAF V600E mutation are diagnostic of hairy cell leukemia (HCL). The treatment of choice is a purine nucleoside analogue — cladribine (2-chlorodeoxyadenosine) as a single course, achieving durable complete remissions in over 85% of cases. FCR is used for CLL. Ibrutinib is used for relapsed/refractory HCL but not first-line. Chlorambucil is ineffective in HCL.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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