Many people are unaware that men can develop breast cancer. These men frequently experience surprize, confusion, and a sense of isolation. For every 100 women who develop breast cancer in the US, one male is diagnosed with the equivalent disease. The overall incidence is between 0.1 and 3.4 cases per 100,000 man-years. This makes male breast cancer one of the rarest malignancies, contributing to the generally low level of public awareness.
Men have glandular breast tissue that is subject to hormonal influences.
Excess estrogen, especially around the time of puberty, has been identified as a possible factor. Men with Klinefelter s syndrome have an increased risk of developing breast cancer, as do men who take estrogens or estrogen-like compounds. Finally, genetic factors have been identified in some cases of male breast cancer. The major problem with gynecomastia is that the differential diagnosis between gynecomastia and breast cancer is sometimes difficult. The most common symptom is a breast mass.