[A case of cystic duct metastasis from rectal cancer]

A 67-year-old man underwent laparoscopic low anterior resection and open medial segmentectomy of the liver for rectal cancer and liver metastasis. During the operation, a cystic duct mass, 1cm in diameter, was found. Therefore cholecystectomy with partial resection of the common bile duct was also performed. The rectal tumor and liver tumor were diagnosed pathologically as moderately differentiated adenocarcinoma. The cystic duct mass was mainly located in the lamina propria and its histological aspects were similar to the rectal cancer. Immunohistochemical staining revealed that rectal, hepatic, and cystic duct lesions were all negative for CK7 but were all positive for CK20. These findings confirmed the diagnosis of rectal cancer with metastases to the liver and the cystic duct. Metastatic cystic duct tumor is extremely rare and has never been reported in the Japanese literature.