Primary signet-ring cell carcinoma of the colon at early stage: a case report and a review of the literature.

A 67-year-old man, who had undergone surgery to resect multiple gastric cancers 4 years ago, visited our hospital for surveillance colonoscopy. Colonoscopy revealed a discolored, 7-mm in diameter, flat-elevated lesion with central depression in the transverse colon near the splenic flexure. Although the findings of endoscopy and barium enema were suggestive of submucosal invasion, the patient chose to undergo endoscopic mucosal resection. Pathological examination of the resected specimen revealed signet-ring cell carcinoma and a positive surgical margin. A second operation was performed, and no residual tumor or metastasis to lymph nodes was found in the resected specimens. Primary colorectal cancers composed of signet-ring cell carcinoma detected and treated at an early stage are extremely rare. We present a case and review the literature.