The simultaneous sequencing of MMR proteins, such as MLH1, MSH2, and MSH6, can further corroborate some cases of MMR-deficient tumors, although no mutation will be seen in cases of hypermethylation of the MLH1 promoter, a common mechanism of somatic acquisition of MMR deficiency (Baudrin et al., 2018), and PMS2 is difficult to sequence due to extensive pseudogenes and homology throughout the genome. The gene discussed is MLH1; the disease is mismatch repair cancer syndrome 1.