Synovial Chondromatosis of the Temporomandibular Joint With Intracranial Extension

A 52-year-old man presented with an extremely rare case of synovial chondromatosis in the temporomandibular joint (TMJ) with extension into the middle cranial fossa manifesting as swelling and exacerbation of pain. He had a long history of right TMJ disorders. Computed tomography and magnetic resonance imaging showed a mass in the right TMJ with extension into the intracranial part through the destroyed temporal skull base. The preoperative diagnosis was chondrosarcoma or osteosarcoma. The patient underwent surgery via combined trans-zygomatic temporal skull base and pre-auricular approaches and the mass was totally removed. Histological examination found an enormous number of closely packed loose bodies of various sizes, consisting of hyaline chondrocytes. The histological diagnosis was synovial chondromatosis. This rare lesion is difficult to discriminate from chondrosarcoma, so total removal is essential for correct diagnosis and cure.