Studies performed by Pettirossi et al to confirm the mechanism of BRAF inhibition in HCL. (Left) Before and (right) after BRAF inhibition with vemurafenib. From top to bottom: (A) phosphorylated ERK and MEK; (B) HCL-related genes with large differences in expression before and after vemurafenib (each column, 1 of 6 patients); (C) bone marrow immunohistochemistry for cyclin D1 and CD20; (D) flow cytometry of the bone marrow aspirate; and (E) confocal microscopy of HCL cells showing loss of hairy morphology. See Figures 1A, 2B, 3A,C, and 4C-D in the article by Pettirossi et al that begins on page 1207.