Prompted by recent studies of mutual exclusivity among BRAF mutation and MAP2K1 mutation in Langerhans cell histiocytosis (LCH) [13–15], as well as work showing distinct functional classes of MAP2K1 mutations [16], we probed a database of clinical specimens with comprehensive genomic profiles for the relationship between MAP2K1 mutations and other driver mutations in melanoma. This evidence concerns the gene MAP2K1 and Langerhans cell histiocytosis.