We report the case of a man in his 60s with a history of hypertension and having soft stools for 3 months. Colonoscopic examination revealed a type 5 rectal tumor. Histopathological examination partially revealed signet-ring cell carcinoma (SRCC) and tubular adenocarcinoma. He underwent intensity-modulated radiotherapy with capecitabine. Thereafter, robot-assisted rectal amputation was performed. His Helicobacter pylori infection had been eradicated; thereafter, he underwent esophagogastrododenoscopy annually. One year and 8 months postoperatively, esophagogastroduodenoscopy revealed multiple verrucous-like elevated lesions in the stomach. Histopathological examination confirmed SRCC. Immunohistochemical analysis showed CK7 negative and CK20 positive. We diagnosed metastatic gastric cancer derived from rectal cancer. FOLFIRI (leucovorin, fluorouracil, and irinotecan) plus ramucirumab therapy was administered; unfortunately he died of peritonitis carcinomatosa after 7 months of gastric metastasis.
