Hidden estrogen production from ovarian remnants leading to progression of disease in metastatic breast cancer

In premenopausal women with hormone dependent breast cancers, ovarian suppression is an important part of treatment, and is often achieved with a bilateral salpingo-oophorectomy (BSO). However, this procedure can lead to ovarian remnant syndrome (ORS), a rare condition where the adnexal tissue is not completely removed and can produce estrogen. We describe a case of ORS in a patient with estrogen receptor positive (ER+) breast cancer who had progression of disease after undergoing a BSO, despite optimal therapy. ORS therefore poses a significant treatment challenge in premenopausal ER+ breast cancer patients thought to be rendered menopausal with a BSO.