Personal History

The majority of breast cancers occur in women over 50, and the disease is most common among women who have reached menopause. Here are some other factors relating to your background and history that can increase the likelihood of your developing breast cancer:

  • Personal history of breast cancer. If you’ve had cancer in one breast, you have a greater chance of developing it in the other breast.

  • Family history of breast cancer. If an immediate relative, such as your mother or sister had breast cancer before 40, you have an increased likelihood of developing it. Having other relatives who have had breast cancer on your mother or father’s side of the family can also increase your risk.

  • Breast density. If you’re 45 or older and mammograms show that you have at least 75% dense breast tissue, you’re at a higher risk. Breast tissue density is generally higher if the breast has more glandular tissue than fat. Not only does this make tumors difficult to see in mammograms, but the dense tissue itself is associated with a greater likelihood of developing cancer.

  • Abnormal breast cells. Some women have breast cells that appear abnormal under a microscope. This can be caused by conditions such as hyperplasia, which is an increase in the growth of cells in a tissue, or lobular carcinoma in situ, or LCIS — also called neoplasia — which is abnormal cells in the breast’s milk-producing glands. These conditions, which are not visible in a mammogram and can only be detected in a biopsy of breast tissue, can increase your risk of developing cancer. Learn more about lobular carcinoma in situ, or LCIS.

  • Radiation therapy. If your chest was exposed to radiation during childhood — for instance, if you were treated for Hodgkin’s disease — you may have a greater chance of developing breast cancer. Studies suggest that the younger you were when you were treated, the higher your risk.

  • Taking DES, or diethylstilbestrol. This synthetic form of estrogen, which was given to some pregnant women in the United States between 1940 and 1971, may lead to a slightly higher incidence of breast cancer. It is not yet known if you have a higher risk of the disease if your mother took DES when she was pregnant with you.

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