MSH2 and neoplasm: BP0001 had a previous diagnosis of Lynch Syndrome and was found to harbour a germline mutation in MSH6 (p.G39E, rs1042821) and a somatic heterozygous deletion encompassing the region encoding for MSH2 and MSH6, resulting in a hemizygous variant in MSH6. PR0103 had a somatic 10 Mb deletion overlapping MSH2 and MSH6 and a 5 kb somatic deletion across MSH2, leading to biallelic loss of MSH2. IHC of MSH2 and MSH6 in both of these patients showed complete loss of protein expression in the tumours (supplementary Figures S5 and S6, available at Annals of Oncology online).