A very rare case of breast cancer in a female-to-male transsexual.

The incidence of breast cancer in female-to-male (FTM) transsexuals who received mastectomy and sex reassignment surgery is very rare. In fact, there is only one previous medical report of such a case. We experienced a case of an FTM transsexual who developed breast cancer 12 years after mastectomy and hysterectomy with bilateral salpingo-oophorectomy. Because he had been continuously receiving testosterone during the last 15 years and because histopathological examination revealed positive estrogen receptor and androgen receptor expression, we suggest that exogenous testosterone may have initiated the development of breast cancer via two distinct pathways. We describe the clinical course and condition of the patient and recommend that medical personnel consider the possibility of hormone-related cancer in FTM transsexuals receiving cross-sex hormones.