Endometriosis and ovarian cancer

In 556 patients undergoing surgery for ovarian cancers the frequency of endometriosis ranged from 3.6% to 5.6% in serous, mucinous, and miscellaneous neoplasms versus 26.3%, 21.1%, and 22.2%, respectively, in endometrioid, clear cell, and mixed subtypes; the differences were statistically significant (chi 2 heterogeneity 50.0, p < 0.001) and consistent in strata of age, parity, menopausal status, and disease stage.