Fig. 2.

Details of three cases with discrepant results between the Idylla microsatellite instability (MSI) assay and the standard polymerase chain reaction (PCR) test. (A–C) Case No. 28, MSI-high (MSI-H) according to the Idylla MSI assay. Standard PCR MSI test is consistent with microsatellite stable (MSS) (A). MSH2 and MLH1 expression is shown in immunochemical staining (B), and next-generation sequencing (NGS) results show MSS pattern (C). (D–F) Case No. 131, MSS (0/7) according to the Idylla MSI assay. Two markers show instability in standard PCR MSI test (arrows, D), and MSH6 and PMS2 protein expressions are shown (E). Repeated NGS shows MSS pattern (F). (G, H) Case No. 133, MSS (0/7) according to the Idylla MSI assay. Two markers show instability in standard PCR MSI test (arrows, G), and MSH6 and PMS2 expressions are shown (H). Repeated NGS analysis was failed. Mutation load, the number of total somatic mutations detected by our NGS panel; TMB, tumor mutation burden, the inferred number of somatic mutations per megabase; I index, the number of insertion or deletion mutations divided by the number of all mutations; IHC, immunohistochemistry