Figure 1.

Detection of microsatellite instability (MSI) or mismatch repair (MMR) deficiency is performed by (A1) Immunohistochemistry of the mismatch repair proteins or (A2) PCR amplification of consensus microsatellite repeats that are analyzed with capillary electrophoresis. Inference of MSI/MMR status from next generation sequencing (NGS) is not presented. (B) MSI/MMR status can be predicted from hematoxylin and eosin (H&E) stained slides, without requiring molecular analyses (see Figure 2). Detection of MSI/dMMR has implications for Lynch Syndrome screening and determining eligibility for immune checkpoint blockade in advanced disease. MSS: microsatellite stable. MSI-H: high microsatellite instability. pMMR: proficient mismatch repair. dMMR: deficient mismatch repair.