The major risk factor for breast cancer is being a woman. Only 1 percent of breast cancer occurs in men.

Some other known risk factors for breast cancer include: family history of the disease, especially in one's mother or sister (it is important to remember that an inherited risk of developing breast cancer can come from the mother's side and also the father's side, so it is important to know your full family history); starting menstrual periods at a young age (early menarche); ending periods at an older age (late menopause); and obesity.

Risk factors do not cause breast cancer, but may contribute to its development. For example, the early onset of menstrual periods is not the cause of breast cancer, but it is thought that a longer time of ovarian cycling and estrogen production leads to more circulating estrogen over many years, which results in greater opportunity for breast cancer development.

A risk factor is anything that can contribute to the likelihood of getting breast cancer, but it is important to know the details that make someone more susceptible to breast cancer:

• Age. A woman's chance of developing breast cancer increases with age. Most occurrences of breast cancer happen in women older than 50. By the time you are in your 30s, you may have a 1-in-233 chance of developing breast cancer. If you live to be 85, your chance is 1-in-8.

• A personal history of breast cancer. If you have had breast cancer in one breast, you have an increased risk of developing breast cancer in the other breast.

• Family history. If you have an immediate family member — mother, sister, or daughter — with breast cancer or ovarian cancer or both, or even a male relative with breast cancer, you will have an increased risk of developing breast cancer in your lifetime. In theory, the more relatives you have that were diagnosed with breast cancer and were premeno-pausal when they contracted it, the higher your own risk will be.

  If you have one first-degree relative (mother, sister, daughter) who contracted the disease before the age of 50 or before menopause, then your chances of getting breast cancer doubles. If you have more relatives that have had breast cancer, then your odds of contracting breast cancer increase even more.

• Obesity. In general, studies indicate that there is a strong correlation between increased weight and breast cancer, especially for those with a weight increase in adolescence or after menopause. Body fat composition in the upper body also increases your risk.

• Radiation exposure. If you received excessive radiation exposure to your chest as a child or young adult, you will have an increased risk of getting breast cancer. And your risk increases if you had radiation to your breast area during your developmental years. For example, women who had radiation treatment to the chest for Hodgkin's disease in their teens have an increased risk of breast cancer.

• First pregnancy at an older age. If you have never been pregnant or you had your first pregnancy after the age of 30, you have a greater chance of developing breast cancer. The theory is that pregnancy provides a mechanism that helps protect breast tissue from estrogen effects.

• Race. It is well documented that white women are more likely to get breast cancer. However, women of African American, Hispanic, or Asian descent are more likely to die of the disease. Studies have shown that these women are diagnosed when they are at a more advanced stage and have a more aggressive tumor.

  Socioeconomic factors, such as income, also influence the disparity of access to screening among different ethnic groups and affect the routine medical care that women in these groups receive or seek, according to studies.

• Hormone therapy. Treatment of postmenopausal symptoms with hormone therapy can increase the risk of breast cancer in those women who have taken hormone therapy for four or more years. The combination of estrogen and progesterone leads to greater risk than estrogen alone. Also, hormone therapy can increase breast density and make it harder to detect tumors on mammograms.

• Birth control pills. The role of oral contraceptives is controversial. Some studies say that the use of birth control pills for four or more years has been associated with an increased risk of breast cancer in pre-menopausal women. The risk is greater for those women who took birth control pills prior to their first pregnancy. That risk may be partially because of delayed first pregnancy, which is also a risk factor.

• Smoking. There are varied theories about smoking and its link to breast cancer. Some studies show no risk and others suggest that there is a link to breast cancer risk. Overall, quitting smoking has great health benefits for all women

• Alcohol consumption. There is controversy regarding the relationship of alcohol consumption to breast cancer risk. Some studies suggest that there is a 20 percent increased risk of breast cancer when women consume one or more alcoholic beverages a day, compared to women who do not drink.

  Fact

  In situ (Latin for “in its original place”) breast carcinoma describes a type of precancerous cells that remain in one location and have not spread to surrounding tissue.

  Other recent studies have indicated that red wine has some protective elements in lowering the risk of breast cancer. In general, it is recommended that a woman limit her consumption of alcoholic beverages to no more than one drink a day.

• Presence of breast carcinoma in situ (e.g., LCIS) and other breast changes (e.g., atypical ductal hyperplasia). These changes are usually discovered after a breast biopsy is performed because of an abnormal mammogram. Changes such as atypical hyperplasia or lobular carcinoma in situ increase one's risk of breast cancer. It is recommended that you develop a monitoring plan through discussion with your doctor and establish a follow-up plan that you are comfortable with.

• Dense breasts. The presence of dense breasts found with a mammogram indicates that there is a high ratio of connective and glandular tissue to fat. This makes it harder to detect masses or tumors with a mammogram. Having dense breasts is typically associated with pre-menopausal women with higher estrogen levels in the body, resulting in greater amounts of dense glandular tissue.