We report a case of an estrogen-producing Brenner tumor of the ovary. A 66-year-old woman presented with a pelvic tumor as revealed by computed tomography scan and was referred to our hospital by a local doctor.
Magnetic resonance imaging revealed a 15-cm-sized solid and multilocular part mixed ovarian tumor with endometrial thickening. Her serum estradiol concentration was 31.6 pg/mL before treatment. We performed a bilateral salpingo-oophorectomy by laparoscopic-assisted surgery and endometrial curettage. The pathological examination of the left ovarian tumor revealed a mucinous and benign ovarian Brenner mixed tumor, with no evidence of malignancy in the endometrial tissue. Postoperatively, her estrogen level decreased to the post-menopausal level. Based on these results, the ovarian tumor was found to be estrogen-producing. The Brenner tumor is generally regarded as a non-estrogen-producing tumor; however, the Brenner tumor, as in this case, may produce estrogen. Therefore, it is necessary to consider changes in the endometrium due to estrogen in the diagnosis and treatment of Brenner tumors.