A systemic review using pooled case series data reclassified into TCGA subgroups of UDEC (n = 73) found 44.0% of cases with MMR deficiency (MMR-d), 12.4% with POLE mutation, and 18.6% with p53 abnormality [22], for which the proportion of UDEC in the MSI group was lower than the previous report (about 60%) [23,24] under this calculation but was consistently higher than the overall EC (28%) in the TCGA cohort [3]. Here, MRC1 is linked to mismatch repair cancer syndrome 1.