Synovial chondromatosis of the temporomandibular joint presenting as a parotid mass: possibility of confusion with benign mixed tumor.

Synovial chondromatosis is a rare metaplastic disorder of synovium in which cartilaginous nodules are produced within joint spaces. An unusual case involving the temporomandibular joint, with extension of the lesion beyond the joint capsule into the parotid gland, is described. The patient had a history of previous superficial parotidectomy for a "benign mixed tumor." Review of the histologic features revealed both lesions to be identical. The reason for confusion between the two diagnoses is discussed.