Early-stage multi-differentiated gastric carcinosarcoma and post-resection local recurrence: a case report

Carcinosarcoma is a rare neoplasm with a poor prognosis that is most often discovered at an advanced stage; a gastric carcinosarcoma is even rarer than carcinosarcomas originating in other organs, such as the uterus. We report our experience with an early-stage multi-differentiated gastric carcinosarcoma.

A 68-year-old male patient presented with anemia, and his fecal occult blood test was positive. An endoscopic examination was conducted which revealed a hemorrhagic, irregular, protruding lesion in the stomach. The lesion was diagnosed as an adenocarcinoma by histopathological examination of the biopsy specimen, and a segmental gastrectomy was performed. A 41 × 29 × 18 mm³ protruding lesion was observed in the resection specimen, and histologically confirmed to be a gastric carcinosarcoma with mixed adenocarcinomatous and sarcomatous composition. Tumor invasion was limited to the submucosa. Besides the adenocarcinomatous portion, neuroendocrine differentiation and AFP-positive gastric carcinoma were present in the carcinomatous portion of the tumor; in the sarcomatous portion, chondrosarcomatous, leiomyosarcomatous, and rhabdomyosarcomatous components were observed in addition to the undifferentiated sarcomatous component. Furthermore, the tumor included SALL4-positive germ cell-like cells. Despite early-stage detection, the cancer recurred locally 14 months after tumor resection, which necessitated a total gastrectomy. At the 2-month follow-up after the total gastrectomy, the patient was alive. This patient had developed an esophageal squamous cell carcinoma and primary lung adenosquamous carcinoma, both of which were resected.

Few cases of early-stage gastric carcinosarcoma have been reported, but there are no reports of recurrence to date. Local recurrence as in this patient, and even in early-stage cases, requires cautious surveillance to check for post-resection recurrence and metastasis. The etiopathogenesis of carcinosarcoma has not yet been elucidated; however, in the present case, despite the tumor's relatively small size, it exhibited various types of differentiation in both the carcinomatous and sarcomatous components and a proliferative germ cell-like portion, which suggests that the monoclonal origin hypothesis may be a valid theory for the carcinosarcoma.