Large synovial osteochondromatosis arising from the interphalangeal joint of the thumb: a case report and review of the literature.

A 38-year-old woman presented with a very large synovial chondromatosis arising from the interphalangeal joint of the thumb. The tumor surrounded the interphalangeal joint and its size was approximately 3 cm. The range of motion was almost fused. Plain radiographs showed an extra-osseous tumor shadow with calcifications. The patient had no local recurrence at one year of follow-up after marginal resection of the tumor and synovectomy. Because this case showed no osteoarthritic changes, it can be classified as primary synovial chondromatosis with a tumor-like nature. Based on the clinical course and pathological report, our synovial chondromatosis case can be classified as Milgram stage 3. Our case report is unique in three respects: i) origin from the interphalangeal joint of the thumb, ii) a single lump of mass and iii) extremely large size. To our knowledge, a similar type of synovial chondromatosis has not been previously reported in the English literature.