Origin of ovarian cancer from benign cysts.

In a case-control study of 1031 epithelial ovarian cancers and 2311 controls conducted in Italy, 56 cases and 116 controls reported history of benign ovarian cysts, corresponding to a relative risk of 1.3 (95% confidence interval = 0.9-1.8). In a subset of 255 histologically reviewed cases, mucinous and endometrioid ovarian neoplasms and neoplasms of stage I or II arose more frequently from cysts, while use of oral contraceptives or parity were not significantly related to history of ovarian cysts.