Mature Testicular Teratoma with Positive Estrogen Receptor Beta Expression in a Transgendered Individual on Cross-Sex Hormonal Therapy: A Case Report.

Estrogen exposure has been linked to a risk of testicular germ cell cancers, although predominantly in animal studies. In the human testis, estrogen receptor beta (ER-β) mediates the physiological action of estrogen. We describe a case of a 30-year-old transgender woman (male-to-female [MtF]) with gender dysphoria who developed a mature testicular teratoma with positive estrogen receptor beta expression while receiving cross-sex hormonal therapy with estradiol and progesterone. Although the presence of hormone receptors does not always imply that hormones have played a role in the development of the tumor, a contribution of exposure to exogenous estrogen in this case cannot be ruled out.