A primary gastric synovial sarcoma

RATIONALE When a gastric spindle cell tumor is observed, the possibility of synovial carcinoma, besides common mesenchymal tumor, should also be considered. PRESENTING CONCERNS OF THE PATIENT The patient is a 51-year-old American woman who underwent medical check-up at a general hospital. Upper endoscopy showed a 2-cm sized mass covered with intact mucosa, and a central depression located on the posterior wall of the mid body. Biopsy of the mass showed focal atypical cells proliferation in mucosa on hematoxylin & eosin (H&E) staining. Endoscopic ultrasound showed a 17-mm homogenously hypoechoic mass within the submucosal layer. INTERVENTIONS After diagnostic endoscopic submucosal dissection was performed, H&E and immunohistochemical staining showed synovial sarcoma (SS). To confirm the diagnosis, reverse transcriptase-polymerase chain reaction was performed, revealing a chimeric transcript of the SYT-SSX1 fusion gene. The diagnosis of primary gastric SS was confirmed because no evidence of possible primary lesions or metastatic lesions was observed. Therefore, the patient underwent distal gastrectomy. OUTCOMES After surgery, the surgical specimen demonstrated no residual tumor cells. The patient received no adjuvant therapy, and there has been no evidence of local recurrence or distant metastasis for 2 months after the operation. LESSONS When gastric subepithelial tumor is suspicious, we should also consider gastric SS.