Skin, Rosai-Dorfman disease, S100 stain

Rosai-Dorfman disease is also known as sinus histiocytosis with massive lymphadenopathy. It is a benign proliferation of histiocytes of unknown etiology. It is most commonly seen in the lymph nodes leading to lymphadenopathy. Skin is the most frequent extranodal site of involvement. Symptoms depend on extent of disease and sites involved. The histiocytes are non-Langerhans type (S100+, CD1a-). Most cases show spontaneous regression. Rare cases are clinically aggressive.

This slide shows S100 stain. See Related Content for H&E stain.