NRAS and Langerhans cell histiocytosis: RAS isoform mutations, such as NRAS and KRAS, occur in 3–7% of ECD, 18% of JXG, 12.5–25% of RDD, and very rarely in LCH patients, while HRAS mutations are rare but are observed in HS patients with concurrent BRAF F595L mutation [11, 26–29].