Though boys and girls begin life with similar breast tissue, over time, men do not have the same complex breast growth and development as women. At puberty, high testosterone and low estrogen levels stop breast development in males. While some milk ducts exist, they remain undeveloped, and lobules are most often absent. However, breast problems, including cancer, can occur in men. For more on breast anatomy, visit the Breast Structure and Function section.
Male Benign Breast Conditions
The benign breast conditions that are most common in women (such as cysts and fibroadenomas) are very rare in men. The most common breast condition in men is gynecomastia (GUY-nuh-ko-MASS-tee-uh) (enlargement of the breast tissue). Gynecomastia results from a hormone imbalance in the body. Certain diseases, hormone drug use, obesity and other hormone changes can cause this imbalance [45]. For example, boys can get a temporary form of gynecomastia during puberty. This condition does not need to be treated unless it is desired or it causes pain. In these cases, it can be treated with hormone therapy or surgery [45].
For more on benign conditions in women, see Benign Breast Conditions.
Male Breast Cancer
Breast cancer in men is rare. However, 1,910 new cases of male breast cancer will be diagnosed in the U.S. during 2009 [5]. In 2005, the overall incidence of breast cancer in men was 1.2 per 100,000, compared to 122 per 100,000 in women. Differences in mortality were equally wide: 0.3 per 100,000 in men; 24 per 100,000 in women [13]. For more statistics on female breast cancer, visit Breast Cancer Statistics.
As with women, invasive ductal carcinoma accounts for most of the breast cancers seen in men. There are few cases of invasive lobular carcinoma and ductal carcinoma in situ in men [46].
The strongest risk factor for male breast cancer is Klinefelter's syndrome, a condition related to high levels of estrogen [45-47]. This rare condition occurs when men are born with two X chromosomes (XXY instead of XY). Although men with Klinefelter's syndrome may have gynecomastia (enlargement of the breast tissue), gynecomastia not related to Klinefelter's syndrome does not appear to increase risk of breast cancer [46,47]. Similar to women, men with a mutation in the BRCA2 gene have an increased risk of breast cancer [45,47]. Chronic alcoholism, chronic liver disease and obesity may also increase the risk of male breast cancer [46,47]. For more on cancer, visit the Breast Facts section. For more information on male breast cancer, see the Treatment section.
Updated 11/11/09
