“…At the far ends of their phenotypic spectra, LCH, ECD, and JXG all have distinct clinical and pathologic features; however, this shared categorization was proposed based on similar molecular alterations, mixed LCH/ECD histiocytic presentations in adult cases, and accumulating data supporting a common hematopoietic precursor, at least between adult LCH and ECD [21]. However, pediatric extracutaneous JXG with MAPK molecular alterations as an L-group histiocytosis, has been less studied in relation to its possible shared origins with LCH and pediatric ECD [10, 16, 38, 40, 46, 51] Furthermore, while the BRAF V600E mutation constitutes the majority of molecular alterations in ECD and LCH [3, 5, 30, 53], only three reported JXG neoplasms, all in male pediatric patients with localized central nervous system (CNS) involvement, are known to harbor the BRAF mutation; however, none showed evidence of systemic disease or a prior history of LCH [56].…”