That is why, drugs targeting DNA repair like PARP-inhibitors, that have already found their way into clinical practice in other cancer entities (26, 27), seem to be a logic therapeutic strategy in our MLH1-/PMS2-/MSH6- digestive system cancer cases as all five cases showed simultaneous mutations (up to 6) in MMR as well as HRR-related genes. This evidence concerns the gene PMS2 and digestive system cancer.