Therefore, a retrospective analysis of 34 additional non-Langerhans cell histiocytoses (16 JXG, 3 adult xanthogranuloma and 1 benign cephalic histiocytosis, both clinical subtypes of JXG, as well as 13 Rosai-Dorfman and 1 Erdheim-Chester disease) for NTRK1, 2 and 3 aberrations was performed. The gene discussed is NTRK1; the disease is Erdheim-Chester disease.