Breast cancer in male-to-female transsexuals: use of breast imaging for detection.

OBJECTIVE: The purposes of this article are to describe two cases of breast cancer in male-to-female transsexuals and to review eight cases previously reported in the literature.
CONCLUSION: Breast cancer occurs in male-to-female transsexuals who receive high doses of exogenous estrogen and develop breast tissue histologically identical to that of a biologically female breast. This exposure to estrogen results in increased risk of breast cancer. The first patient described is a male-to-female transsexual with screening-detected ductal carcinoma in situ and a family history of breast cancer. The other patient is a male-to-female transsexual with invasive ductal carcinoma that was occult on diagnostic digital mammographic and ultrasound findings but visualized on digital breast tomosynthesis and breast MR images. The analysis of the eight previously reported cases showed that breast cancer in male-to-female transsexuals occurs at a younger age and is more frequently estrogen receptor negative than breast cancer in others born biologically male. Screening for breast cancer in male-to-female transsexuals should be undertaken for those with additional risk factors (e.g., family history, BRCA2 mutation, Klinefelter syndrome) and should be available to those who desire screening, preferably in a clinical trial.