MSI-H endometrial cancers are enriched for mutations in ARID1A, PTEN, CTCF, PIK3CA, and JAK1 while MSI-H gastric cancers frequently harbor ARID1A, KMT2D, RNF43, KMT2B, and TP53 mutations [11, 13]. The gene discussed is ARID1A; the disease is endometrial cancer.