In cases of LCH without the BRAF V600E mutation, other mutations have been reported, including ARAF (one patient of two BRAF wild-type cases) [167] and MAP2K1 (MEK1) mutations [7/21 (33%) to 11/22 (50%) of BRAF wild-type cases] [168,169]. This evidence concerns the gene MAP2K1 and Langerhans cell histiocytosis.