Risk of borderline ovarian tumors among women with benign ovarian tumors: A cohort study

Objective. A growing number of studies suggest that some ovarian cancers can arise from benign and borderline ovarian tumors. However, studies on the association between benign and borderline ovarian tumors are lacking. We studied the overall-and histotype-specific risk of borderline ovarian tumors among women with a benign ovarian tumor. Methods. This nationwide cohort study included all Danish women diagnosed with a benign ovarian tumor (n = 139,466) during 1978-2012. The cohort was linked to the Danish Pathology Data Bank and standardized incidence ratios (SIR) with 95% confidence intervals (CI) were calculated. Results. Women with benign ovarian tumors had increased risks for subsequent borderline ovarian tumors (SIR 1.62, 95% CI 1.43-1.82), and this applied to both serous (SIR 1.69, 95% CI 1.39-2.03) and mucinous (SIR 1.75, 95% CI 1.45-2.10) histotypes of borderline ovarian tumors. The risk for borderline ovarian tumors was primarily increased for women diagnosed with a benign ovarian tumor before 40 years of age. The risk remained increased up to 9 years after a benign ovarian tumor diagnosis. Finally, the associations did not change markedly when analyzed for the different histotypes of benign (solid and cystic tumors) and borderline (serous and mucinous tumors) ovarian tumors. Conclusions. Women with benign ovarian tumors have a long-term increased risk for borderline ovarian tumors. However, as all associations in this study were only adjusted for age and calendar period of diagnosis, more studies that are able to adjust for additional potential confounding variables are required to further understand these associations. (C) 2017 Elsevier Inc. All rights reserved.