The incidence of mismatch repair gene defects in colorectal liver metastases.

Knowledge of the molecular biology of primary colorectal cancer (CRC) has improved in recent years, and one reason for this is the identification of microsatellite instability (MSI), which occurs in up to 15% of sporadic CRC. However, less is known regarding the processes involved in colorectal liver metastases (CRLM). Increasing numbers of patients with CRLM are suitable for curative resection, so the identification of molecular markers may improve patient selection. The aim of the present study was to characterise the incidence of MSI in resected CRLM. Fifty‑one sequentially resected CRLM specimens were selected. Clinicopathologic data was collated and immunohistochemistry for MLH1 and MSH2 was performed on paraffin sections of the CRLM specimens. The association between abnormal staining and the clinicopathological data was examined. The median age of the subjects in the current study was 65 years, the average number of CRLM was 2 and the median overall survival time was 42.1 months post liver resection. None of the 50 resected specimens demonstrated abnormal staining for MLH1 or MSH2. Compared with the previously reported incidence of MSI in primary CRC, the low incidence of MSI in the current cohort of CRLM precludes its use as a marker for use in making clinical decisions regarding this condition.