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.

• Keywords: Colorectal neoplasms;Microsatellite repeats;Sequence analysis;