A Rare Case of Rosai-Dorfman Disease Affecting the Brachial Plexus: A Case Report.

Sinus histiocytosis with massive lymphadenopathy or Rosai-Dorfman disease is a rare but well-established entity, commonly affecting the lymph nodes of the head and neck. Extranodal presentation, affecting the central nervous system, eye orbit, kidneys, testis, bones, upper respiratory tract, lungs, thyroid, small intestine, and peritoneum, has been reported. We present a case of a rare presentation of Rosai-Dorfman disease affecting the brachial plexus.