Fig. 1.

Comparison between deficient mismatch repair (dMMR) by immunohistochemistry (IHC) and microsatellite instability (MSI) status by polymerase chain reaction (PCR) analysis in 3800 cancers (according to Jaffrelot et al. [10], more study data: Tab. S1, online). IHC classic: Concordant findings between dMMR (complete loss of MLH1/PMS2 or MSH2/MSH6) and MSI-PCR (evidence of MSI-H). IHC abnormal: Unusual findings, e.g., isolated loss of MMR protein or contradictory findings between MMR-IHC and MSI-PCR analysis. PCR-FN (false negative): MSS/MSI‑L PCR finding despite classic dMMR determined by IHC. [values in columns: % of the respective tumor group] CRC colorectal cancer, EC endometrial cancer, other GI non-colorectal gastrointestinal tumors (9 × stomach, 5 × small intestine, 4 × duodenum, 3 × bile duct, 2 × pancreas, 1 × hepatocellular); other: 12 × sebaceous skin tumors, 6 × ovarian and 4 × urothelial cancer, and 1 × each of glioblastoma, sarcoma, melanoma, and neuro-endocrine tumor