Cutaneous rosai-dorfman disease is a distinct clinical entity

Rosai-Dorfman disease (RDD) is a rare but distinctive clinicopathologic entity of unknown etiology affecting lymph nodes as well as extranodal sites. Although cutaneous involvement in RDD is common, purely cutaneous disease is rare and not well documented. We report 22 patients with cutaneous and superficial subcutaneous RDD. The lesions presented as papules and nodules, often with discoloration (9/22) and frequent multifocality (13/22), without predilection for a specific site of the body. Age distribution was wide and ranged from 15 to 68 years, with a median of 43.5 years. Of the 17 patients for whom information on racial background was available, 7 were Asian, 8 were white, and 2 were black, with a marked female predominance (2:1). The lesions resolved in 6 of 13 patients for whom follow-up data were available, regardless of the treatment given. Lesions persisted or recurred in 7 patients. Histologically, the lesions are invariably characterized by a proliferation of polygonal S100-positive histiocytes showing emperipolesis and a mixed inflammatory infiltrate. This study characterizes the histologic spectrum of cutaneous RDD in regard to variation in the numbers of typical S100-positive histiocytes and emperipolesis, variation in the quality and quantity of the inflammatory response, and the degree of stromal fibrosis, which resulted in a strikingly storiform growth pattern in six lesions and a lobulated pattern in two lesions. Whereas the clinical as well as histologic appearance of the cutaneous and subcutaneous lesions in the purely extranodal forms of RDD is indistinguishable from that of systemic RDD, this study emphasizes that purely cutaneous RDD is a distinct clinical entity in regard to its epidemiology and remains localized to the skin even with long-term follow-up. Patients with purely cutaneous RDD are of an older age at onset of disease (median = 43.5 years), with a reversed male/female ratio. There are no significant systemic extracutaneous or serologic manifestations. Whereas systemic RDD is commonly seen in blacks and only rarely reported in Orientals, the majority of the patients in this series with purely cutaneous RDD are Asians and whites.