B-RAF is a member of the RAF-family of kinases which plays an important role in the RAS-RAF-MEK-ERK mitotic signaling pathway. Mutations of B-RAF have been described in up to 40-70% of Langerhans cell histiocytosis and approximately 50% of Erdheim-Chester disease. The hotspot for mutations in BRAF is at codon Val600 and these are activating mutations. The most common activating mutation is p.Val600Glu(V600E). Various B-Raf inhibitors(Vemurafenib, Dabrafenib) have been FDA approved for therapy for some tumor types in certain settings, and clinical trials for advanced BRAF V600 mutation-positive tumors using targeted therapy (often in combination with other therapy) may be available (clinical trials.gov).