Prevalence of endometriosis in ovarian cancer.

Endometriosis may be the precursor of clear cell or endometrioid ovarian cancer. In this review, we focus on the prevalence of endometriosis in ovarian cancer and related clinical and epidemiological issues. According to 15 published reports, the rank order of the prevalence of endometriosis in each histologic type was clear cell (39.2%) > endometrioid (21.2%) > serous (3.3%) > mucinous type (3.0%). The high prevalence of endometriosis in clear cell and endometrioid types is a consistent finding in Japan and western countries. However, the incidence of the clear cell type is much higher (15-20% vs. 7-8%), and that of the endometrioid type is lower (7-16% vs. 18-26%), in Japan compared with western countries. This review is also concerned with the relationship between the presence of ovarian endometriosis and clinical features such as age, parity, menopausal status, clinical stage, and survival in ovarian cancer patients.