“…According to the 2016 histiocytoses classification criteria, RDD, including classical, extranodal, RDD associated with neoplasia or immune disease, and unclassified RDD types, belongs to the R group of histiocytoses ( 8 ). RDD occurs mainly in the lymph nodes, with about 40% in extranodal organs ( 9 ). RDD has a predominantly single systemic involvement, in which skin, bone, and soft tissue are most frequently involved.…”