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XXY Males (Klinefelter's Syndrome) and Breast Cancer

Men at increased risk


Updated June 23, 2006

The nature of the problem
Human beings have 23 pairs of chromosomes. The 23rd pair is the sex chromosome pair, which in males is usually XY. However, some males have an extra X chromosome, resulting in three sex chromosomes, or XXY. All cells in the body may have this set of three, or only some cells may have it (called mosaicism).

Whether it's all or some cells that are affected, the condition may lead to a set of consequences in the body which has in the past been termed Klinefelter's syndrome. Not all males with the extra X chromosome will develop the syndrome, but for those that do develop it, there are numerous health consequences. In this article, "XXY" will refer to males who would previously have been considered to have Klinefelter's syndrome.

Increased risk of breast cancer
XXY boys do not progress normally through puberty. Their testes remain child-sized and therefore do not produce enough of the male hormone testosterone. As adolescents, XXY boys are taller than average and may lack facial hair. About one-third of XXY boys will develop enlarged breasts, a condition known as gynecomastia. This is different than just fat accumulation that gives the appearance of having breasts--it is true breast development.

These males with enlarged breasts have the same risk of breast cancer as women do. In other words, XXY males are 20 to 50 times more likely than the average male to develop breast cancer. Unlike women, though, XXY males are more likely to develop cancer in both breasts or unusual second types of cancer.

Regular examination important
For these reasons, XXY males--both adolescents and adults--need to practice regular breast self-examination. Although XXY males have other health problems such as infertility and a slightly increased risk for autoimmune disorders, breast cancer is certainly the most potentially life-threatening. It is recommended that XXY males have regular thorough breast examinations done by a medical professional.

Psychosocial aspects
XXY males aware of their rare disorder no doubt feel alone, as many people with rare disorders do. As adolescents, they may have been taunted by other teens about their height and muscle weakness, or if their breasts developed noticeably. Add to this, then, an XXY male facing male breast cancer, itself a rare condition (just 0.2 percent of all cancer in men). In the public's view, breast cancer is considered a female disease, so XXY males with the disease may feel their masculinity further threatened. Most literature on the subject, support groups, and even awareness efforts are directed at women. The XXY male's physician may not be familiar with male breast cancer or how to treat it. All of these factors can make an XXY male feel isolated and perhaps cause him to delay seeking treatment or even deny that he is at risk for breast cancer.

Testosterone treatment
Since the testes of XXY males remain small and do not produce enough testosterone, XXY teens entering puberty benefit from receiving testosterone injections. The hormone increases strength and muscle size, promotes the growth of facial and body hair, and gives the teen's body a more masculine appearance. The literature reviewed for this article did not state what effect, if any, testosterone injections might have on breast development, but it would seem that the injections would suppress breast development as it does in the average adolescent boy.

Treatment with testosterone injections may, therefore, offer a significant reduction in the risk XXY males face for breast cancer. Testosterone treatment is known to reduce an XXY male's risk of developing osteoporosis later in life. Research has shown that even beginning testosterone injections in adulthood can be beneficial. Whether testosterone treatment can also beneficial for reducing breast cancer risk should also be investigated.

Information for this article was taken from:
- Understanding Klinefelter Syndrome, online publication from the National Institute for Child Health and Development.
- About Male Breast Cancer, online publication from interact.withus.com.

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