Synovial sarcoma arising in the posterior pharyngeal wall confirmed by molecular detection of SYT gene split: case report

Synovial sarcoma is a primitive mesenchymal tumor which occurs most frequently in soft tissues. Some unusual locations of synovial sarcoma could lead to diagnostic challenges. In this study, we reported a case of primary synovial sarcoma arose in the posterior pharyngeal wall. X-ray examination showed a space-occupying lesion in the post-pharyngeal wall. Frozen section and conventional histopathological diagnosis suggested that it could be mucinous-rich fibroblastic tumor. Immunohistochemistry results showed that vimentin was diffusely expressed in tumor tissue. However, epithelial membrane antigen (EMA) was expressed focally. To further identify the tumor, SYT gene split, a specific characteristic of synovial sarcoma cells was detected using FISH. It was found that over 10% of tumor cells had SYT gene split in the nucleus. In combination with the morphology and immunohistochemistry results, it was finally diagnosed with monophasic synovial sarcoma, which occurs at a very unusual site.