A 73-year-old woman underwent a sigmoidectomy April 30, 1999, after being diagnosed with sigmoid colon cancer. The histopathological diagnosis was moderately differentiated adenocarcinoma (se, INF β, ly2, v1, n0). After the first operation, the serum CEA value increased a second time, and a tumor to the cranial side of a hepatic cyst with a diameter of 10 cm and transformation around the cyst was observed by CT in January 2000. An exploratory aspiration and biopsy of the tumor showed a high CEA value in the cystic fluid (38, 900ng/ml) and a moderately differentiated adenocarcinoma was identified. A right lobectomy, including the hepatic cyst, was performed on March 25. Macroscopically, the tumor measured 6×5cm and was located in segment 8. It pressed against the hepatic cyst. Microscopically, the cancer cells had infiltrated the tissue near the cystic wall but were not found inside the cyst. The serum CEA value decreased to 3.7ng/ml six months after the second operation, and no signs of recurrence have been observed. The relation between serum and hepatic cyst CEA values may be of interest in cases of hepatic metastasis of colon cancer.