Of note, two participants each had a CRC that showed loss of all four MMR proteins, where one tumor (SLS135) was from a carrier of a germline MSH2 pathogenic variant explaining the loss of MSH2/MSH6 expression but where the loss of MLH1/PMS2 expression was unexplained, while the other tumor (SLS272) had no cause for loss of expression of all four MMR proteins during pre-study clinical investigations. The gene discussed is MSH2; the disease is neoplasm.