Subsequently, BRAFV600E was also detected in other histiocytic disorders,7,8 and alternative somatic alterations in genes of the mitogen-activated protein kinase (MAPK) signaling pathway were identified in histiocytoses without the BRAFV600E mutation.9, 10, 11, 12, 13, 14, 15, 16, 17 Together, these findings established histiocytic disorders as hematologic neoplasms characterized by a notable dependence on MAPK signaling.18 This evidence concerns the gene WNK2 and hematopoietic and lymphoid system neoplasm.