Ovarian cancer in endometriosis: epidemiology, natural history, and clinical diagnosis.

We review whether endometriosis-associated ovarian cancer is a specific entity compared with ovarian cancer not associated with endometriosis, with respect to epidemiology, natural history, and clinical diagnosis; we present a review of the English-language literature for ovarian cancer in endometriosis with respect to these three features. A recent prospective study in Japan directly showed that, during a follow-up of up to 17 years of an ovarian endometrioma cohort (n = 6398), 46 incident ovarian cancers were identified, showing that the ovarian cancer risk was significantly elevated in patients with ovarian endometrioma (standardized incidence ratio [SIR], 8.95; 95% confidence interval [CI], 4.12 to 15.3). Advancing age (>40 years) and the size of the endometriomas (>9 cm) were independent predictors of the development of ovarian cancer among the women with ovarian endometrioma. Although some endometriosis lesions may predispose to clear cell carcinoma (CCC) and endometrioid adenocarcinoma (EAC) of the ovary, both of these cancers differ from the other histological types with respect to their clinical characteristics and carcinogenesis. In patients with endometriosis-associated ovarian cancer, benign-appearing ovarian masses are typically present several years before the diagnosis of the cancer. A slightly elevated carbohydrate antigen [CA] 125 level is also typically present many years before the diagnosis in these patients. However, serous-type ovarian cancer may exhibit a rapid progression possibly through de-novo carcinogenesis. Ovarian endometrioma could be viewed as a neoplastic process, particularly in perimenopausal women. Understanding the mechanisms of the development of endometriosis and elucidating its pathogenesis and pathophysiology are intrinsic to the prevention of endometriosis-associated ovarian cancer and the search for effective therapies.