Cutaneous Rosai-Dorfman disease: a case report.

A 40-year-old female presented with a 2-year history of asymptomatic nodules on her lower extremity. Symptoms began with a small dark spot on the right thigh, which progressively enlarged. She then developed similar nodules on her right leg and a lesion on her left buttock. On physical exam, her right proximal lateral thigh revealed a 10 cm x 6 cm indurated, pink-brown, heterogeneous plaque with a hyperpigmented rim. A similar 8 cm x 4 cm indurated plaque was on the distal right thigh. There was also a 3 to 4 cm hyperpigmented, thin plaque on the left posterior lower extremity and on the left inferior lateral buttock. Exam revealed no cervical or supraclavicular lymphadenopathy or organomegaly. Preliminary work-up by her primary physicians included serology for Lyme disease, systemic lupus erythematous, thyroid function tests, blood cultures for mycobacteria, and angiotensin-converting enzyme, which were all negative or within normal limits. Biopsies demonstrated a nodular inflammatory infiltrate within the dermis consisting of histiocytes with local aggregates of plasma cells and lymphocytes. Histiocytes were enlarged with vesicular nuclei. Some plasma cells had prominent Russell bodies, and emperipolesis was observed. Histiocytes stained positively for S-100, CD68 and CD45, while CD1A, CD30, and CD21; microorganism stains were negative.