Spontaneous regression of colorectal liver metastasis.

A 72-year-old woman with advanced ascending colon cancer and an intraductal papillary mucinous neoplasm (IPMN) of the pancreatic head was treated by right hemicolectomy (RHC) and pylorus-preserving pancreaticoduodenectomy (PpPD). Adjuvant chemotherapy was not administered. Multimodal examinations at 5 months after surgery detected a solitary metastatic liver tumor derived from cancer of the ascending colon. Liver resection proceeded at 7 months after the first surgery. A pathological study of a surgical specimen of the liver identified a necrotic nodule that did not contain viable tumor cells. However, an immunohistological study of the hepatic mass indicated metastasis derived from cancer of the ascending colon. These findings were consistent with total necrosis of a liver metastasis of colorectal cancer. The mechanism of spontaneous regression of tumors remains unexplained. In our case, pancreaticoduodenectomy was performed at the same time as right hemicolectomy, which involved a risk of continuous biliary infection after biliary tract reconstruction. A host immune response to chronic biliary tract infection might have been involved in the spontaneous regression of liver metastasis. Spontaneous regression of colorectal liver metastasis is rare, and the mechanism remains unknown. This needs to be investigated in more tissues from patients who have experienced this phenomenon.