Cutaneous Rosai-Dorfman disease.

Sinus histiocytosis with massive lymphadenopathy, or Rosai-Dorfman disease, is a benign idiopathic histiocytic proliferative disorder that commonly involves the lymph nodes but secondarily may involve the skin. However, purely cutaneous disease without lymphadenopathy or internal organ involvement rarely may occur. We present case reports of three patients who presented with asymptomatic nonspecific enlarging skin nodules without evidence of lymphadenopathy or internal disease. Histopathologic examination of skin lesions in all patients showed proliferation of large histiocytes with phagocytosed inflammatory cells characteristic of Rosai-Dorfman disease. However, the diagnoses of dermatofibroma, other spindle cell neoplasm, infectious granulomatous process, and other xanthohistiocytic proliferations were also considered due to the presence of storiform spindle cells and foamy cells in the first case. One patient experienced regression during a course of oral steroids, while another patient cleared spontaneously. In the absence of massive lymphadenopathy characteristic of Rosai-Dorfman disease, the diagnosis of purely cutaneous Rosai-Dorfman disease may be complicated by the rarity, non-specific clinical appearance of skin lesions, and broad histopathological differential diagnosis of this disorder. A high index of suspicion of the clinician and pathologist is often required.