BRAF and hairy cell leukemia: The detection of a heterozygous mutation in BRAF gene resulting in a V600E variant protein in all 48 patients with classical HCL and none of 195 patients with other B-lymphoid leukemia or lymphomas was a remarkable cornerstone in defining the pathogenesis of this leukemia and led to trials investigating the role of BRAF inhibitors in HCL [9, 11, 39] Initial trials investigated the potential role of monotherapy with the BRAF inhibitor, vemurafenib and demonstrated the significant efficacy of the small molecule inhibitor in treating patients with relapsed HCL [11].