Superficial depressed early carcinoma that developed into protuberant advanced carcinoma in the transverse colon

A screening colonoscopic examination in a 70-year-old man revealed a nonpolypoid type superficial depressed early carcinoma, about 2cm in diameter, in the transverse colon. The lesion was not resected and was observed because of coexisting nonresectable hepatocellular carcinoma (HCC). Fifteen months later, follow-up examinations revealed a polypoid type protuberant advanced carcinoma, about 6 cm in diameter, at the same site. Because complete response of the HCC had been induced by transarterial embolization, the colon carcinoma was operatively resected. There is an indefinite concept that colorectal carcinomas develop without substantial morphological changes, and no superficial depressed carcinoma that developed into a protuberant type advanced carcinoma has been reported. The case reported here provides evidence that some polypoid carcinomas arise from superficial depressed precursors. There is some intermingling between the two postulated colorectal carcinogenic pathways, the conventional polypoid pathway named the "adenoma-carcinoma sequence", and the nonpolypoid pathway, including so-called "de-novo" carcinogenesis.