Simultaneous colonic metastasis of advanced gastric cancer: a case report

BACKGROUND: Although distant metastasis in gastric cancer can be present at the time of the initial diagnosis, colonic metastasis is extremely rare. This report describes a case of simultaneous colonic metastasis of advanced gastric cancer. CASE PRESENTATION: The patient was a 78-year-old woman with nausea and epigastric pain. Upper gastrointestinal endoscopy revealed an advanced invasive ulcerative tumor in the lesser curvature of the stomach extending from the anterior to the middle portion. Colonoscopy revealed a 4-mm polyp-like lesion in the mid-transverse colon; therefore, a polypectomy was performed. Both gastric and colonic tumors showed poorly differentiated adenocarcinoma with signet ring cell carcinoma. After providing informed consent, the patient underwent a total gastrectomy. Histologic examination showed similar morphologic features of both gastric and colonic tumors. Immunohistochemistry staining showed that these tumor cells were positive for cytokeratin (CK) 7 and negative for CK20. CONCLUSIONS: This was an extremely rare case of simultaneous colonic metastasis of advanced gastric cancer. Because missed metastasis can result in a poorer prognosis, we propose a systemic search including colonoscopy for patients with advanced gastric cancer, especially cases involving poorly differentiated adenocarcinoma or signet ring cell carcinoma. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40792-023-01622-x.