Diagnosis of microsatellite instability-positive colorectal cancer.

The continuing increase in knowledge regarding the genetic basis of carcinogenesis has led to diverse efforts to exploit this knowledge clinically, primarily in the form of predictive genetic testing. In conjunction with family history, gene tests are intended to improve individual cancer risk assessment. At present, genetic testing for colorectal cancer (CRC) risk--in the form of microsatellite instability (MSI) screening and DNA sequencing--is applied in hereditary nonpolyposis colorectal cancer (HNPCC). In this inherited colorectal tumor syndrome, determining the genetic status may result in an individually tailored surveillance program and prophylactic treatment, reducing cancer morbidity and mortality.