Sinus Histiocytosis with Massive Lymphadenopathy (Rosai-Dorfman Disease) and Anaplastic Large Cell Lymphoma

Sinus histiocytosis with massive lymphadenopathy (SHML) is a rare and benign cause of lymphadenopathy and was first described in 1969. This disease commonly presents in children and young adults with supra-diaphragmatic lymphadenopathy mainly at cervical nodal sites, composed of a population of histiocytes. Since its description, over 400 cases have been described, but there are few reports in the literature on its association with lymphomas. This case report describes a case with co-existing SHML and anaplastic large cell lymphoma (ALCL). The diagnosis of SHML in our patient did not alter the clinical outcome and the patient responded well to treatment for ALCL. Clinicians should maintain a high index of suspicion in cases of infra-diaphragmatic SHML for the presence of occult lymphoma. LEARNING POINTS: A rare presentation of sinus histiocytosis with massive lymphadenopathy (SHML) with anaplastic large cell lymphoma in the same lymph node at the same time is described. SHML has no proven clinical significance. A diagnosis of SHML in the presence of infra-diaphragmatic lymphadenopathy should raise a high index of suspicion for lymphoma.