Sigmoid colon carcinoma that developed from a sessile-type cancer in a short period of time

We report a case of sigmoid colon carcinoma that developed from a sessile-type cancer in a short period of time. An 83-year-old man was found to have a round sessile polyp, about 2 cm in diameter, in the sigmoid colon. Because he had taken anticoagulants, immediate endoscopic mucosal resection and biopsy were not performed. Forty-three days later, the apical surface of the sessile polyp had become depressed and ulcerated, and we judged that an endoscopic resection was not indicated for this lesion. The histologic diagnosis of the biopsy specimens was a well-differentiated adenocarcinoma. We recommended surgical treatment; however, the patient was not in favor of surgical treatment and would not consent to surgery. Two more examinations were performed and the tumor was found to have developed into an invasive cancer with ulcerated, nodular margins involving 3/4 of the colonic lumen. At 271 days after the initial examination, the patient finally consented to surgery and a partial resection of the sigmoid colon was performed. The tumor was classified as stage I (T2N0M0). The several examinations performed from presentation within a short time span provide evidence of the morphologic changes that occur when a sessile-type cancer develops into an ulcerating invasive cancer. We hypothesize that remarkable configuration changes and development take place when a tumor becomes invasive in the muscularis propria from massive submucosal invasion. Our findings suggest that among the tumors discovered as typical ulcerating invasive type colon cancers are those that developed from protuberant tumors in a short period of time.