Synovial chondromatosis: Rare involvement of metacarpophalangeal joint and diagnostic challenges in MR imaging.

Synovial chondromatosis (SC) is a rare benign tumor of the cartilaginous tissue that frequently affects large joints intra-articularly. Characteristic imaging findings were reported for the diagnosis of SC. Herein, we report a case of SC of the metacarpophalangeal joint with atypical MRI findings. Considering the clinical presentation, erosion, absence of calcification on X-ray and CT, and low intensity on short tau inversion recovery (STIR), tenosynovial giant cell tumor was the initially diagnosis. However, histopathological findings revealed SC with fibrosis, which was confirmed using Elastica Van Gieson (EVG) staining. In general, low intensity on STIR in SC indicate calcification; however, it can also represent fibrosis in SC. In this case, the diagnosis of SC using MRI was limited highlighting the importance of histopathological findings for an accurate diagnosis of SC.