Department of Pathology, The Cancer Institute Hospital of Japanese Foundation for Cancer Research (JFCR), Tokyo, Japan.
Division of Pathology, Cancer Institute, JFCR, Tokyo, Japan.
Pathol Int. 2020 Dec;70(12):1015-1019. doi: 10.1111/pin.13020. Epub 2020 Sep 17.
Synovial sarcoma is a high-grade soft tissue sarcoma that occurs primarily in the deep soft tissue of extremities, and primary colorectal synovial sarcoma is extremely rare. In this report, we present a synovial sarcoma mostly located within the mucosa of the sigmoid colon. The patient was a man in his forties with a germline deletion in the MSH2 gene. He had experienced undifferentiated pleomorphic sarcoma of the left forearm 7 years before and adenocarcinoma of the transverse colon 6 years before, both of which were successfully treated and exhibited no recurrence to date. A surveillance colonoscopy for Lynch syndrome revealed the tumor which had a submucosal tumor-like appearance with central erosion and endoscopic resection was performed. Histologically, it was composed of monotonous proliferation of spindle cells arranged in cellular fascicles; these findings were compatible with monophasic fibrous synovial sarcoma. In the tumor cells, the presence of the SS18-SSX1 fusion gene was confirmed. Protein expression of mismatch repair genes was intact in the tumor cells, indicating the association between microsatellite instability and synovial sarcoma was weak. The present case highlights a rare primary site of synovial sarcoma in a patient with Lynch syndrome.
滑膜肉瘤是一种高级别的软组织肉瘤，主要发生在四肢深部软组织，而原发性结直肠滑膜肉瘤极为罕见。本报告介绍了一例主要位于乙状结肠黏膜内的滑膜肉瘤。患者为一名四十多岁的男性，存在 MSH2 基因种系缺失。他在 7 年前曾患有左前臂未分化多形性肉瘤，6 年前患有横结肠癌，均经成功治疗且至今无复发。林奇综合征的监测性结肠镜检查发现了该肿瘤，其具有黏膜下肿瘤样外观，中央有溃疡，遂进行了内镜下切除。组织学上，由排列成细胞束的单调梭形细胞增殖构成；这些发现与单相纤维滑膜肉瘤相符。在肿瘤细胞中，存在 SS18-SSX1 融合基因。肿瘤细胞中错配修复基因的蛋白表达完整，表明微卫星不稳定性与滑膜肉瘤之间的关联较弱。本病例强调了林奇综合征患者滑膜肉瘤罕见的原发性部位。
