PTEN and ovarian cancer: Only a few TSG genes acting in a recessive manner have been identified as somatically mutated or methylated in ovarian cancer, including TP53 (48%) [24], PTEN (21% in the endometrioid subtype) [25], RB1 (7-10%) [26], and CDKN2A (79% in the mucinous subtype) [27].