Of the 24 cases of benign ovarian neoplasms and the 21 cases of borderline ovarian neoplasms, only 4 (8.9%) borderline lesions showed p16 immunostaining scores of 4 or more, whereas all 46 (100.0%) cases of malignant ovarian neoplasms showed p16 immunostaining scores of 4 or greater. This evidence concerns the gene CDKN2A and ovarian cancer.