A case of cutaneous Rosai-Dorfman disease (CRDD) with underlying calvarial involvement and absence of BRAFV600E mutation

CRDD: cutaneous Rosai-Dorfman disease LCH: Langerhans cell histiocytosis RDD: Rosai-Dorfman disease R osai-Dorfman disease (RDD) is a benign histiocytic proliferation that most commonly presents with painless bilateral lymphadenopathy and constitutional symptoms such as fever, fatigue, and night sweats. RDD is considered by many to be a reaction pattern with several different manifestations, especially as clonality has not been documented to support it representing a neoplasm per se. Classic histologic features include histiocytes that are S100 protein positive, are CD1a , and demonstrate emperipolesis. Cutaneous lesions can occur in about 10% of patients, however, RDD limited only to cutaneous involvement is particularly rare. Moreover, concomitant cutaneous RDD (CRDD) and bone RDD has rarely been reported in the English-language literature. Here, we presented a case of CRDD on the scalp with underlying bony involvement.