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

BACKGROUND: 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. CASE PRESENTATION: 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 mm(3) 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. CONCLUSIONS: 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.