MSH2 and Leigh syndrome: Recent genetic analyses suggest that more than 5–10% of patients with pancreatic cancer carry rare germline variants such as ATM, BRCA1, BRCA2 and Lynch syndrome (LS)-related four DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6 and PMS2) (Solomon et al., 2012; Lucas et al., 2014; Jóri et al., 2015; Hu et al., 2018; Hsu et al., 2021).