Endometriosis increases the risk of endometriosis-associated ovarian cancer (EAOC). Although the issue is still controversial, the malignant transformation of endometriotic lesions seems more plausible than a mere risk factor sharing between endometriosis and ovarian cancer. As a consequence, an effective endometriosis suppressive medical treatment, like dienogest, could reduce at least some subtypes of estrogen sensitive ovarian cancer, like the endometrioid one. Endometriosis medical treatment aim is to control pain and to reduce surgery. The potential and still speculative ovarian cancer preventive effect could be a further suggestion to increase compliance to a long lasting treatment, while adequate clinical trials are necessary to confirm this hypothesis.