The MSI-PCR test developed in this study.

A Workflow of microsatellite PCR analysis. The MSI-PCR test contains five poly-A mononucleotide MS markers. A marker was defined unstable in the tumour if the shift was equal to or larger than 3 bp in the major band or if new minor bands were present compared with those in the corresponding non-tumourous tissue. For the ones showing an inconclusive smearing pattern, the PCR products were re-run in a high-resolution gel to visualize the PCR bands more clearly. MSI-H: two or more of the five microsatellite markers show instability. MSI-L: one of the five microsatellite markers shows instability. MSS: no markers show instability. B Representative images of the MSI-PCR gel electrophoresis. The left panel, the MSS result. The middle panel, an MSI-H result with the major DNA products shifted by 3 bp or larger in the tumour. The sizes of the major DNA products are shown on the bottom of the gel images. The right panel, an MSI-H result with presentation of new minor DNA bands in the tumour, as compared with the non-tumourous region. T, tumour. N, non-tumourous region.