Cutaneous rosai-dorfman disease: a clinical and histopathologic study of 25 cases in China.

Cutaneous Rosai-Dorfman disease (CRDD) is a rare proliferative disorder of histiocytes with unknown etiology, broadly different from systemic Rosai-Dorfman disease. We present the largest series of CRDD, describing the clinical manifestation, histopathology, immunohistochemistry, and follow-up course of 25 cases in China. Clinically, 39 skin lesions in 25 patients were divided into 3 main types: papulonodular type (79.5%), indurated plaque type (12.8%), and tumor type (7.7%). Extremities were the most frequently involved, followed by trunk and face. None of the patients was found to have visceral organ involvement or lymphadenopathy. Microscopically, CRDD was characterized by scattering, clusters or sheets of large polygonal histiocytes intermingled with a florid, mixed inflammatory infiltrate. The most important feature was emperipolesis, which can be highlighted by S-100 protein stain. Patch and bandlike infiltrate of numerous mature plasma cells around glands and vessels was a constant finding in all lesions. Neutrophils existed in all cases to a variable degree with 2 cases forming microabscess. Four cases were remarkable for fibrosis, and xanthomatous change was observed in 2 cases. Coexistence of localized Langerhans cell histiocytosis and CRDD was interestingly found in case 7, which was evidenced by CD1a stain. Clinical follow-up in 22 patients, ranging from 2 to 55 months, indicated that surgical excision was the exclusive effective treatment for CRDD. Partial or complete spontaneous remission was achieved in 7 patients within 6 to 55 months. Owing to its favorable outcome, CRDD should be differentiated from a variety of benign and malignant lesions. Recognition of its wide clinical spectrum and histologic features combined with S-100 protein stain can help to establish the correct diagnosis.