Two cases of cutaneous Rosai-Dorfman disease

Rosai-Dorfman disease (RDD) or sinus histiocytosis with massive lymphadenopathy (SHML) is a benign, idiopathic histiocytic proliferative disorder affecting lymph nodes as well as extranodal sites. It is accompanied by fever, leukocytosis, elevated erythrocyte sedimentation rate, and polyclonal hypergammaglobulinemia. Although cutaneous involvement in RDD is common, a purely cutaneous disease is very rare. Histologic findings show characteristic large, pale, histiocytic cells exhibiting cytophagocytosis (emperipolesis). Immunohistochemically, these histiocytes are positive for S-100 protein and CD68, but negative for CD1a. The etiology is unknown, although it is thought to be a reactive disorder rather than neoplastic. We report two cases of Rosai-Dorfman disease showing involvement limited to the skin.