Detection of Mismatch Repair Deficiency in Endometrial Cancer: Assessment of IHC, Fragment Length Analysis, and Amplicon Sequencing Based MSI Testing.

Mismatch repair (MMR) deficiency can be indicative of Lynch syndrome (LS) and guide treatment with immune checkpoint inhibitors. Colorectal cancers (CRCs) and endometrial cancers (ECs) are routinely screened to identify LS, primarily using immunohistochemistry (IHC) or microsatellite instability (MSI) testing, but concordance between these methods is variable in ECs. Here, we investigate this variability in 361 ECs from the Ohio OCCPI/OPTEC ( = 196) and Manchester PETALS ( = 165) trials, where concordance between assays differed significantly.