What is an estrogen-producing tumor? what causes it?

Over expression: A number of different malignancies have been associated with production of estrogen. Many are ovarian tumors such as granulosa cell tumors and thecomas. Estrogen-producing endometrioid adenocarcinoma resembling sex cord-stromal tumor of the ovary and Sertoli cell tumors of the testis,and adrenal tumors have also been reported to produce increased levels of estrogen.