Rare tumors of the ear, nose and throat: synovial sarcoma of the head and neck.

Synovial sarcoma is a rare neoplasm of mesenchymal origin. Contrary to earlier beliefs, this tumor does not arise from the synovial lining of joints and bursae, but develops from pluripotential mesenchymal cells through abnormal differentiation into synovial neoplasms. Macroscopically there are no distinguishing features. Microscopically the tumor is characterized by a biphasic pattern of pseudoepithelial cells and a spindle cell element with fibrosarcomatous appearance. To establish a diagnosis both features must be present, yet their relative proportions vary markedly. The tumor occurs most frequently in the extremities and rarely in other areas. Only 19 cases of synovial sarcoma of the head and neck have been reported in the literature. Two additional cases, one of the hypopharynx and one of the cheek, are reported herein.