Retroperitoneal synovial sarcoma conirmed by molecular detection of SYT gene rearrangements

The case of a 47-year-old woman with retroperitoneal synovial sarcoma is described. her presenting symptom was severe left upper abdominal and back pain. On radiologic study, bulky retroperitoneal soft tissue mass was detected superior to the left kidney, which showed solid and cystic components. Multiple lung and bone metastases were also detected. Diagnostic surgical resection was performed and the mass was removed en bloc with the left kidney. There was well-deined border between the tumor and the kidney or the adrenal gland. Histologically, the tumor was characterized by a uniform proliferation of small rounded cells and it was dificult to diagnose this on hematoxylin-eosin staining. Immunohistochemical examination was further performed and, because of its immunoreactivity for CD99 and bcl-2, synovial sarcoma was speculated as probable differential diagnosis. Subsequently, luorescence in situ hybridization (FISH) analysis was performed and demonstrated prominent SYT gene rearrangements in the neoplastic cells indicating SYT-SSX1 gene fusion, which is a distinctive inding of synovial sarcoma. Based on these indings, inal diagnosis was primary retroperitoneal synovial sarcoma. Postoperatively, she drastically developed dissemination of metastatic disease and died three months after surgery. retroperitoneal synovial sarcoma is an extremely rare malignant tumor with high mortality and recurrence rates. histological or immunohistological diagnosis of synovial sarcoma is quite dificult, especially in the case of the small rounded cell type. In this report, the differential diagnosis of small rounded cell tumors including retroperitoneal synovial sarcomas are discussed. The gene based diagnostic evolution including FISH analysis is also discussed.