Activating mutations in BRAF were found in CLL (N = 3 of 39 patients; two with BRAF G469A and one with BRAF V600E), multiple myeloma (N = 1 of 17; BRAF V600E), hairy cell leukemia (HCL) (N = 1 of 1; BRAF V600E) and Erdheim Chester disease (ECD) (N = 1 of 1 patient; BRAF V600E). Here, BRAF is linked to hairy cell leukemia.