Ovarian neuroendocrine tumor metastases can induce estrogen production in postmenopausal patients.

Neuroendocrine tumors (NETs) are malignant neoplasms that can be associated with specific hormonal syndromes. We describe a novel syndrome of postmenopausal vaginal bleeding and ovarian estradiol overproduction due to ovarian NET localizations. An extensive workup was performed for 2 index patients with ovarian metastases of small bowel neuroendocrine tumors and symptoms of postmenopausal vaginal bleeding. Clinically significant ovarian estrogen production was demonstrated by a combination of ovarian vein sampling and normalization of circulating estrogen levels after oophorectomy. Immunohistochemical analyses revealed marked aromatase immunoactivity in the ovarian NET cells, while CYP17A1 and SF-1 were detected in the adjacent ovarian stromal cells but not the NET cells. Ex vivo and in vivo endocrine tests were unable to identify a paracrine mechanism of ovarian estradiol overproduction by NET cells. A retrospective search of electronic medical records revealed that 21% (14/66) of postmenopausal patients with an ovarian NET localization reported symptoms of vaginal blood loss. Together, these findings support the presence of a novel NET-associated hormonal syndrome.