What is the relationship between endometriosis and epithelial ovarian cancer?

Historic hypotheses regarding the pathogenesis of endometriosis and epithelial ovarian cancer are not entirely consistent with epidemiologic and biologic data. Alternatively, inflammation may also play an important role in the development of these conditions. Epidemiological, histopathological and molecular data suggest endometriosis may be a precursor lesion for the development of endometrioid or clear cell epithelial ovarian cancer. Endometriosis is more prevalent in patients with endometrioid and clear cell epithelial ovarian cancer. Hyperplastic and atypical endometriosis may be candidate lesions in the pathogenesis of these types of ovarian malignancies. Endometriosis also has neoplastic characteristics on a molecular level and it shares a common molecular lineage with endometrioid and clear cell ovarian cancer. Finally, the relationship between endometriosis and epithelial ovarian cancer has clinical implications in the diagnosis, treatment and prognosis of these conditions and in recommending hormone replacement therapy to women with endometriosis.