Hairy cell leukemia (HCL) is distinguished from other B-cell leukemias by expression of CD25 and annexin A1, as well as a pathognomonic mutation in:

• A MYD88 L265P
• B NOTCH1
• C SF3B1
• D BRAF V600E ✓

Explanation

BRAF V600E is present in virtually all cases of classic hairy cell leukemia and is pathognomonic; it activates MAPK signaling and is the therapeutic target of BRAF inhibitors (vemurafenib) in refractory HCL. MYD88 L265P is characteristic of lymphoplasmacytic lymphoma (Waldenstrom macroglobulinemia) and activated B-cell type DLBCL. NOTCH1 mutations are found in CLL and T-ALL. SF3B1 mutations characterize CLL and myelodysplastic syndrome with ring sideroblasts.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.