Extranodal Castleman disease of the extremities: a case report and review of the literature.

Castleman disease is a rare lymphoproliferative disorder of unknown etiology that most commonly presents as a mediastinal nodal mass or, in the extranodal form of the disease, a mass located in the mediastinum or retroperitoneum. It is exceptionally uncommon for Castleman disease to present in the extremities. We report a rare case of extranodal Castleman disease presenting as a muscular forearm mass. We compare our case with the seven other reported cases in which Castleman disease presented as an isolated soft tissue mass in the extremities.