Primary Synovial Sarcoma of the Bone: A Case Report and Literature Review

Synovial sarcoma (SS), a spindle cell sarcoma, typically occurs in the soft tissues of the extremities and rarely develops in the bones as a primary tumor. To our knowledge, no case of SS in the metacarpal bone has been reported.

We report a case of primary SS of the metacarpal bone. Considering the clinical and imaging findings, SS was difficult to diagnose; therefore, we performed an open biopsy. Next, we performed a wide resection following the management guidelines for SS of the soft tissue. Immunohistochemistry (IHC) showed positive staining for SS18:SSX and SSX, and fluorescence in situ hybridization showed positive staining for the SS18 split. Owing to FNCLCC grade 3 tumor and the R1 margin, adjuvant chemotherapy with ifosfamide and doxorubicin was initiated. Finally, SS of the bone was diagnosed. Furthermore, we reviewed a total of 37 published cases of primary bone SS, including our case. Age and sex were almost the same in all cases of bone SS, and the most frequent site was the long bone in the lower extremity.

IHC for SS18::SSX and SSX antibodies are beneficial for diagnosing general SS and SS of the bone. Moreover, SS of the bone should be considered in the differential diagnosis of spindle cell sarcomas of the bone. Wide resection and chemotherapy are recommended as current treatment strategies, although further studies are required regarding treatment validity.