AT-rich interactive domain 1A (ARID1A), also known as BAF250a, is a tumor suppressor that is typically mutated in Epstein-Barr virus-positive and microsatellite instability-high (MSI-H) gastric cancer [10, 11], ovarian clear cell carcinoma [12], endometrial cancer [13], and non-small cell lung cancer [14]. The gene discussed is ARID1A; the disease is ovarian clear cell cancer.