Rosai-Dorfman disease of the parotid gland: cytologic and histopathologic findings with immunohistochemical correlation.

Rosai-Dorfman disease is a rare histiocytic proliferative disorder of unknown origin and a distinct clinicopathologic entity also known as sinus histiocytosis with massive lymphadenopathy. The disease can involve extranodal tissues and rarely can present as salivary gland enlargement without significant lymphadenopathy. Involvement of the extranodal head and neck sites appears to be more common in patients with immunologic abnormalities. The disease was first described in 4 patients in 1969, and with later descriptions of more patients, the disease was established as a well-defined clinicopathologic entity. The characteristic pathologic feature of this disease is proliferation of distinctive histiocytic cells that demonstrate emperipolesis in the background of a mixed inflammatory infiltrate, consisting of moderately abundant plasma cells and lymphocytes. Fine-needle aspiration biopsy can be helpful in establishing the correct diagnosis, since surgical treatment is not necessary other than obtaining tissue for definitive diagnosis. We describe cytologic, histopathologic, and immunohistochemical features of a case of Rosai-Dorfman disease that involved a major salivary gland without significant lymphadenopathy in a 48-year-old patient with systemic lupus erythematosus. We also briefly discuss possible causes and pathogenesis and review the literature.