V-raf murine sarcoma viral oncogene homolog B (BRAF) mutations in hairy cell leukaemia

Hairy cell leukemia (HCL) is a B-cell non-Hodgkin lymphoma with distinct clinical, morphological and immunophenotypic features; however, there are many other B-cell lymphomas, which closely mimic HCL. Accurate diagnosis of HCL is important as treatment with 2-chloro-2'-deoxyadenosine (cladribine) is associated with >80% chance of complete cure. The recent description of BRAF p.V600E mutations in almost all HCL cases in various studies has not only improved the pathogenetic understanding of this entity but also increased the diagnostic accuracy of this disorder.

The aim of the study was to standardize a molecular test for diagnosis of HCL and compare with standard established morphological, cytochemical and immunophenotypic parameters for HCL diagnosis.

The incidence of this mutation was sought in 20 patients with either classical HCL or HCL variant (HCLv) by Sanger sequencing and allele-specific polymerase chain reaction. BRAF p.V600E mutation was present in all HCL cases and absent in the only HCLv case.

A high degree of correlation was noted between the presence of BRAF p.V600E and established diagnostic criteria in 20/20 patients with HCL/HCLv. Our data supports the observation that this mutation is present in all cases of HCL and is absent in HCLv. Hence, detection of the BRAF p. V600E mutation can be a useful adjunct in the diagnostic algorithm.