Abstract

Synovial chondromatosis is a rare benign disorder that can closely mimic chondrosarcoma, particularly in the temporomandibular joint (TMJ), where both conditions are uncommon. We report a diagnostically challenging case of an 81-year-old female presenting with preauricular pain, swelling, and limited mouth opening. Radio logic evaluation, including computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography-computed tomography (PET-CT) revealed multiple calcified loose bodies, condylar erosion, and a poorly defined mass, initially suggesting synovial chondromatosis. Surgical intervention was performed under the assumption of a benign lesion. However, histopathologic examination demonstrated high-grade (grade III) chondrosarcoma with marked cellular atypia and increased mitotic activity. This case highlights the limitations of relying solely on clinical and radiologic findings for diagnosis. Accurate differentiation between synovial chon dromatosis and chondrosarcoma requires comprehensive evaluation, including histopathologic confirmation. Clinicians should maintain a high index of suspicion when atypical or aggressive imaging features are present in TMJ lesions. (J Korean Dent Assoc 2026; 64(7): 259-264)