Cancer risk after hospital discharge diagnosis of benign ovarian cysts and endometriosis

Background. The aim was to evaluate whether patients with benign ovarian cysts, functional ovarian cysts, or endometriosis have an increased risk of developing gynecologic cancer. Methods. The Swedish Hospital Discharge Register was used to identify a cohort of women discharged from hospital with the diagnoses of ovarian cyst (n = 42 217), functional ovarian cyst (n = 17 998), or endometriosis (n = 28 163). To each case, three controls were matched. The National Swedish Cancer Register matched all incident cancers diagnosed among cases and controls. From the Fertility Register, the date of birth of children born to the cases and controls were obtained. Results. Women with endometriosis had an increased risk for ovarian cancer (OR 1.34; 95% CI 1.03-1.75), but no association was found between ovarian cysts or functional cysts and ovarian malignancy, including all ages. Young women (15-29 years old) discharged from hospital for ovarian cysts and functional cysts showed an increased risk of developing ovarian cancer later in life (OR 2.2; 95% CI 1.3-3.9 and OR 1.8; 95% CI 1.5-2.0), as well as women with ovarian cysts who had undergone ovarian cyst resection or unilateral oophorectomy (OR 8.8; 95% CI 5.2-15). The risk of developing ovarian cancer was inversely related to parity. Mean age at diagnosis was significantly lower in all three study groups. Conclusion. In this study women with endometriosis and young women who had undergone surgery with removal of an ovarian cyst had an increased risk of developing ovarian cancer.