Mutations in ARID1A are frequent across carcinomatous types, present in over 30–50% of ovarian and endometrial carcinomas, 10% of hepatocellular and urinary bladder carcinomas, and 5–10% of colorectal, gastric, and non-small cell lung carcinomas [7, 9]. The gene discussed is ARID1A; the disease is urinary bladder carcinoma.