TisN0M1 Sigmoid Colon Cancer: A Case Report.

Distant metastasis of a colon carcinoma in situ has not yet been reported. We experienced a case of a sigmoid colon carcinoma in situ with common hepatic lymph node metastasis. After the first operation, we diagnosed dual intramucosal adenocarcinomas of the sigmoid colon without any regional lymph node metastasis. After the second operation, a metastatic adenocarcinoma was found in the common hepatic lymph nodes. We suggest that metastasis in cases of a colonic carcinoma in situ is rare, but possible. The parallel progression model of tumors can explain this early metastasis.