The advent of massively parallel sequencing made it possible in 2011 to discover, starting from the whole-exome analysis of just one patient with HCL,20 that the causal genetic lesion of this cancer was a single somatic, clonal, point mutation in the DNA sequence of BRAF, a kinase-encoding proto-oncogene that, at the time, was little known in hematologic malignancies. The gene discussed is BRAF; the disease is cancer.