Real-world experience of BRAF V600E mutation testing in hairy cell leukaemia

Hairy cell leukaemia (HCL) is a rare, mature, B-cell malignancy characterised clinically by fatigue, splenomegaly, pancytopenia and recurrent opportunistic infections. Morphologically, hairy cells have prominent cytoplasmic projections with classical HCL (HCLc) cells immunophenotypically expressing CD11c, CD19, CD25 and CD103. A variant form (HCLv), that lacks CD25 expression, exhibits a more aggressive clinical course and may not respond to standard HCLc therapies.1 The discovery of the acquired BRAF V600E mutation (c.1799T\u003eA; p.Val600Glu) in nearly all cases of HCLc in 2011, but absent in those patients with HCLv, has added an additional level to the diagnostic algorithm with current guidelines recommending molecular testing for the BRAF V600E in the diagnostic work-up.1–4 In order to establish adherence to guidelines, a retrospective audit was performed on a series of patients with HCL …