Testing tumors for microsatellite instability.

The methods for determining microsatellite instability in tumors are highly heterogeneous. Recently a 5-marker panel of microsatellites was suggested for this purpose. In this review attention is drawn to the fact that microsatellite instability can be assessed by analyzing tumor DNA with a single marker, BAT-26, and that normal tissue DNA from the same individual needs to be analyzed only when an aberrant allele is seen in the tumor. Whilst this simple procedure does not distinguish between different types and degrees of instability, it should be sufficient for many purposes, such as screening colorectal cancers for mismatch repair deficiency.