Rosai-Dorfman disease, or sinus histiocytosis with massive lymphadenopathy, is a benign histiocytic proliferation that can cause large lymph node masses, most often cervical. Visceral damage is not rare. Diagnosis requires histologic examination: intrasinus histiocytic proliferation with cells showing emperipolesis or lymphocytophagocytosis. These histiocytes have a normal activated phenotype. Association with immunological abnormalities or autoimmune events, most often autoimmune cytopenia, is possible. This association is a poor prognostic factor. Clinical course is generally spontaneously favorable. There is nonetheless a substantial risk of compression associated with large tumor masses, especially in cases of retro-orbital or epidural involvement. Expectant management is most often appropriate. Treatment is reserved for forms that are directly threatening, progressive, or when poor prognostic factors are present. The treatment, when it is indicated, is not codified. It combines, according to the individual case, surgery, corticosteroids, antimetabolites and interferon alpha.