Breast cancer usually happens when certain cells located in the breast start to grow out of control, taking over nearby tissue and spreading throughout the body. Large collections of this infected tissue are called "tumors". Some tumors are not even considered to be cancer because they cannot spread throughout the body or threaten a person's life. These types of tumors are called "benign tumors". The types of tumors that do spread throughout the body and invade the tissues around the breast are considered to be cancer and have been given the name "malignant tumors". It is said that any type of tissue in the breast can form some type of cancer, but it mostly comes from either ducts or glands. It can take months or even years for a tumor to get big enough for someone to actually feel it in their breast, so they are encouraged to be screened for tumors by a mammogram. Mammograms are designed to detect any type of disease before a person even begins to feel it. Breast cancer is the most common "malignancy" that affects women in America and throughout Europe. Every single woman is at risk of getting breast cancer and almost 200,000 cases of were said to be diagnosed in the United States in 2001. It is the second highest cause, behind lung cancer, of cancer deaths among women in North America. The types of risk factors for breast cancer are divided into two types, those you can't change and those you can change. The factors associated with increasing your risk of breast cancer that your can't change include: just being a woman, getting older, or having some type of family history or a relative with breast cancer. Other risk factors are having your menopause late, having children past the age of thirty, or contracting a genetic mutation that would somehow increase your risk. Certain types of risk factors that you can change are: - not taking hormone replacement therapy (HRT), which means that long term uses of estrogens for menopause symptoms does in fact slightly increase your risk. - stopping the use of birth control pills, because it is noted that ten years following the cessation of The Pill, a woman's risk of breast cancer reverts to what it would have been if she had not used this form of birth control. However, neither of these risks are as significant as the ones that are associated with your gender, age, and family history. All the factors are based on probabilities, and that means that a person without any of those mentioned is still subject to developing breast cancer and the best way to be sure is to get the proper screening and detection for breast cancer development. There are preventative measures that can be taken, up to a point. It is noted that a drug called Tamoxifen is not used widely as a prevention, but it has been proved to be helpful in some cases. There is also a limited amount of data that suggests that Vitamin A may be useful in the prevention of breast cancer, but further research is needed to prove this. The most important step for a woman to prevent breast cancer is to schedule regular checkups, screenings and mammograms, learn how to perform her own exams, and also to acquire all the information she can about the subject.