Four of the 30 (13%) OCSs lacked evidence of TP53 mutation by genetic and IHC analyses, and three of the four tumors harbored mutations involving KRAS (one G12A and one G12D), RPL22 (one frameshift), ARID1A (one frameshift), and/or CTNNB1 (one with S37C) that are often seen in non-HGSC ovarian carcinomas. The gene discussed is ARID1A; the disease is ovarian carcinoma.