MAP2K1 and Langerhans cell histiocytosis: This mutation strongly activates BRAF kinase activity, leading to constitutive activation of the MAPK pathway and subsequent activation of MEK1 and MEK2 proteins, thereby promoting cell proliferation and inhibiting apoptosis.25 As early as 2010, LCH was classified as a neoplastic disorder based on the BRAF V600E mutation.