CD1A and sinus histiocytosis with massive lymphadenopathy: Juvenile xanthogranuloma, which is a non-Langerhans cell histiocytic proliferation, was excluded due to its localization, while Langerhans cell histiocytosis, which is on the other end of the spectrum, is differentiated from RDD with the absence of emperipolesis, the presence of a smaller and notched nucleus, and CD1a positivity.