PMS2 and Leigh syndrome: However, only in 2017, was the first case of pancreatic NEN and IHC confirmation in LS was reported: a 65-year female with LS and a history of two CRCs, EC, and ductal mammary neoplasia was diagnosed with non-functioning pancreatic NEN (loss of expression of MLH1 and PMS2 was identified via IHC and MSI through PCR) [75].