In particular, AT-rich interactive domain-containing protein 1A (ARID1A) is the most frequently mutated SWI/SNF subunit in cancer [2], with the highest mutation frequency in gynecologic cancers, i.e. ovarian clear cell carcinomas, ovarian endometrioid carcinomas, and endometrial endometrioid carcinomas [3–7]. The gene discussed is ARID1A; the disease is endometrial endometrioid carcinoma.