Synovial sarcoma (SS) is a malignant soft tissue neoplasm that occurs in various parts of the human body, but most commonly affects the extremities. Its diagnosis of synovial sarcoma often requires adjunctive techniques such as immunohistochemical staining and molecular studies, especially for synovial sarcoma at unusual locations. SS at a gastrointestinal location is exceedingly rare. We report here three cases of primary gastric synovial sarcoma. Malignant gastric mesenchymal tumor has many differential diagnoses other than synovial sarcoma, such as gastrointestinal stromal tumor (GIST), leiomyosarcoma, schwannoma, malignant peripheral nerve sheath tumor (MPNST) and so on. In our three cases, using reverse transcription polymerase chain reaction (RT-PCR) and direct sequencing, we detected an SS18-SSX1 fusion gene, which is specific to synovial sarcoma. In addition, we found the reduced expression of SMARCB1/INI1 in the tumor cells in two of the three cases. Through histopathological, immunohistochemical, and molecular analyses, we confirmed the diagnosis of primary gastric synovial sarcoma.
Keywords: INI1; SS18-SSX1; Stomach; Synovial sarcoma.
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