The etiology of cancer of the adnexa is uncertain. Several conditions have been hypothetically considered: incessant ovulation, excessive gonadotropin secretion, retrograde carcinogen transport (asbestos and talc), and estrogen/progesterone imbalance. Familial accumulation constitutes about 10% of the cases while the rest are spontaneous. Obese women have a higher frequency of borderline tumors.
Increasing number of births and use of birth control pills provides a certain degree of protection, which is likely due to the reduced number of ovulations. Use of birth control pills for more than 5 years can reduce the risk of ovarian cancer by > 50%. Longer use reduces the risk even further, likely due to prevention of ovulation. Tobacco smoking may possibly also reduce the risk.
Repeated ovulation with repair of surface epithelium is assumed to be of significance for epithelial ovarian cancer. The risk appears to be related to the number of ovulations during a woman's fertile years.
In a Norwegian study, it was found that 6% of patients with epithelial ovarian cancer had mutations in the BRCA 1 or BRCA 2 genes.
For dysgerminomas, genetic conditions are of significance to a certain degree; around 5% occur in phenotypical women with abnormal gonads such as 46XY (bilateral streak gonads), 46X/46XY (unilateral streak gonad, contralateral testis) or 46XY (testicular feminization).