After conditional depletion of either ARID1A (n = 10) or simultaneously ARID1A and PTEN (n = 12), the mice with knock-out of only ARID1A did not develop histological alterations, whereas 40% of the mice with double knock-out of ARID1A and PTEN developed poorly differentiated ovarian tumors disseminating in the peritoneal cavity and ascites. Here, ARID1A is linked to ovarian neoplasm.