[A case of signet-ring cell type cancer of the colon].

A rare case of a primary signet-ring cell carcinoma of the sigmoid colon in a 66-year-old man is reported. Endoscopically, a sessile polyp, 2 cm in diameter, was found in sigmoid colon, consisting mainly of a well differentiated adenocarcinoma and, partially of a signet-ring cell carcinoma. A residual polyp was found at the same site in the sigmoid colon, sixth months after surgery. The resected polyp was histologically confirmed as being a signet-ring cell carcinoma, which had infiltrated into submucosal space by scirrhous invasion. After a polypectomy, a partial colectomy was performed and no carcinoma cells have been identified in the resected colon. We have speculated that this signet-ring cell polyp could develop into Borrmann type 4 advanced colon cancer.