Department of Pathology, Cancer Research Institute and Department of Surgery, Seoul National University College of Medicine, Seoul 110-799, Korea. woohokim@snu.ac.kr
ABSTRACT
BACKGROUND: Microsatellite instability (MSI), which is caused by a deficient mismatch repair system, is seen in most of the hereditary non-polyposis colon cancers and a portion of sporadic colorectal cancers.
METHODS: Two hundreds forty-six consecutive sporadic colorectal cancer patients were analyzed for MSI using an ABI 377 automatic sequencer and fluorescent dye-labelled primers (BAT-25 and BAT-26).
RESULTS: The overall incidence of MSI in studied cases was 9.8% (24/246). This incidence is lower than most of the reported incidences in western countries. The incidence of MSI tumors in the proximal colon was 29.6%, while that of the distal colon was only 4.2% (p<0.001). MSI in sporadic colorectal cancers was more prevalent in poorly differentiated adenocarcinoma. In contrast to western countries, mucinous carcinoma did not show higher incidence of MSI.
CONCLUSION: The results suggest that MSI frequently occurs in cancers of the proximal colon and in tumors with poorly differentiated histology.