PIK3CA and neoplasm: Besides MMR gene alterations, analysis of tumor tissue of the ten MMRD cases revealed frequent genetic variants in ATRX (8/10, 80%), NF1 (5/10, 50%), PDGFRA (4/10, 40%), PIK3CA (4/10, 40%), SETD2 (8/10, 80%), and TP53 (10/10, 100%).