Synovial chondrosarcoma of the temporomandibular joint: A case report

Synovial chondrosarcoma (SCS) is a rare malignant cartilaginous tumor. Twenty-one cases have been described in the literature.(1-14) SCS may arise in a case of preexisting synovial chondromatosis (SCM) or as a primary malignant tumor of the synovium.(4) A literature review shows that the common sites for the occurrence of synovial chondrosarcoma are the knee, followed by the hip, ankle, groin, and elbow.(12) The age of occurrence ranges between 30 and 70 years, with two thirds of the patients predominately women, in the fifth to the seventh decades of life. Most patients have a soft tissue mass with pain and joint dysfunction. There are similar clinical, radiologic, and histologic features that can create difficulty in distinguishing SCS from SCM. Radiographs of SCS show evidence of a soft tissue mass involving the joint. Some patients have clumps of calcified material within the soft tissue mass and marginal erosion of the articular bone. Grossly, the joint cavity is filled with thickened synovial tissue containing pearly white to blue glistening nodules with areas of mucoid material. Some of the nodules are situated free in the joint cavity, and others are within the adjacent soft tissue. Microscopically, SCS is composed of atypical cartilage. The nodules of chondroid tissue are separated by fibrous septa. The chondrocytes, especially at the periphery of the tumor, show pleomorphism with bizarre, binucleated, and multinucleated cells with large irregular, hyperchromatic nuclei and granular eosinophilic cytoplasm. Mitosis is rare. The cells lie in a basophilic mucoid stroma or in lacunae. Foci of calcification, myxoid degeneration, and necrosis are often present. The chondroid tissue is directly derived from the synovium. The purpose of this report is to describe a rare case of SCS occurring in the temporomandibular joint (TMJ). This appears to be the only reported case of SCS originating in the TMJ.