Breast cancer happens when cells in the breast begin to grow out of control and can then invade nearby tissues or spread throughout the body. Large collections of this out of control tissue are called tumors. However, some tumors are not really cancer because they cannot spread or threaten someone's life. These are called benign tumors. The tumors that can spread throughout the body or invade nearby tissues are considered cancer and are called malignant tumors. Theoretically, any of the types of tissue in the breast can form a cancer, but usually it comes from either the ducts or the glands. Because it may take months to years for a tumor to get large enough to feel in the breast, we screen for tumors with mammograms, which can sometimes see disease before we can feel it.
The most important risk factors for the development of breast cancer cannot be controlled by the individual. There are some risk factors that are associated with an increased risk, but there is not a clear cause and effect relationship. In no way can strong recommendations be made like the cause and effect relationship seen with tobacco and lung cancer. There are a few risk factors that may be modified by a woman that potentially could influence the development of breast cancer.
If possible, a woman should avoid long-term hormone replacement therapy, have children before age 30, breastfeed, avoid weight gain through exercise and proper diet, and limit alcohol consumption to 1 drink a day or less. For women already at a high risk, their risk of developing breast cancer can be reduced by about 50% by taking a drug called Tamoxifen for five years. Tamoxifen has some common side effects (like hot flashes and vaginal discharge), which are not serious and some uncommon side effects (like blood clots, pulmonary embolus, stroke, and uterine cancer) which are life threatening. Tamoxifen isn't widely used for prevention, but may be useful in some cases. There are limited data suggesting that vitamin A may protect against breast cancer but further research is needed before it can be recommended for prevention. Other things being investigated include phytoestrogens (naturally occurring estrogens that are in high numbers in soy), vitamin E, vitamin C, and other drugs. Further testing of these substances is also needed before they can be recommended for breast cancer prevention.
Right now, the most important thing any woman can do to decrease her risk of dying from breast cancer is to have regular mammogram screening, learn how to perform breast self exams, and have a regular physical examination by their physician. For more information on breast cancer prevention.
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