A person’s health and medical history can affect their risk of developing breast cancer. In this section, we’ll explore some of the factors that are linked to an increased risk of breast cancer, including lobular carcinoma in situ, dense breast tissue, early exposure to large amounts of radiation, and some benign breast conditions.

Lobular carcinoma in situ, or LCIS, is a condition in which large numbers of abnormal cells grow inside the lobules of the breast. Although the term LCIS includes the word “carcinoma,” LCIS is not breast cancer. LCIS is linked to an increased risk of invasive breast cancer. Women with LCIS are 7 to 11 times more likely to develop cancer in either breast than those without LCIS. Most cases of LCIS occur before menopause. The average age at diagnosis is 44 to 46 years old. Women with LCIS who also have a 20% or higher lifetime risk of breast cancer may follow special screening guidelines to help detect cancer early. If you have LCIS, you should see your health care provider for a clinical breast exam and risk assessment every 6 to 12 months starting at age 25 and get a mammogram with digital breast tomosynthesis every year starting at age 30. You should also talk with your health care provider about starting yearly breast MRI screening at age 25. This care can help ensure that if cancer does develop, it’s caught early, when survival rates are highest. In addition to screening, talk with your health care provider about the risks and benefits of your risk reduction options to choose the one that’s right for you. The National Comprehensive Cancer Network strongly recommends that women with LCIS take a risk-reducing drug, such as tamoxifen, to reduce their risk of breast cancer. The use of a risk-reducing drug is the preferred option for lowering breast cancer risk because it offers similar benefits to surgery without the need for a risk-reducing mastectomy. For more information, you can visit the Risk Factors section on komen.org.

Breast density refers to how breast tissue appears through a mammogram. It’s not a measure of how your breasts feel. You wouldn’t know you had dense breasts unless you had a mammogram. Breast density compares the area of your breast tissue seen on a mammogram to an area of fat. Since tissue is denser than fat, this difference shows up on a mammogram. High breast density means there’s more breast tissue than fat. This is linked to an increased risk of breast cancer. Dense breast tissue can appear white or light gray on a mammogram. This may make abnormal findings harder to identify on a mammogram as they may also appear white or light gray.

Because young women usually have dense breasts, this can make their mammograms harder to interpret. After menopause, most women’s breast tissue is replaced by fat and their breast density decreases. This makes mammograms easier to read for postmenopausal women. The Food and Drug Administration now requires all mammography centers in the U.S. to notify women about their breast density after getting a mammogram. Although, there are no special recommendations or screening guidelines for women with dense breasts. However, by looking at your mammogram or the measure of breast density, your health care provider may determine you have dense breasts and may recommend additional types of breast imaging along with regular mammograms. For more information, you can visit the Risk Factors section on komen.org.

Benign breast conditions are non-cancerous breast disorders. There are many different types of benign breast conditions and they can occur in both women and men. Your health care provider may use the term fibrocystic change to describe a range of benign breast conditions. Some of these conditions are linked to an increased risk of breast cancer while others are not. The benign breast conditions linked to risk are categorized as either non-proliferative breast conditions or proliferative breast conditions. Non-proliferative breast conditions don’t have fast growing cells and don’t appear to increase the risk of breast cancer. Proliferative breast conditions are defined as non-cancerous disorders where breast cells start to multiply more than usual. Although they aren’t cancerous themselves, these cells are linked to an increased risk of breast cancer. The most common type of proliferative breast condition is called hyperplasia. There are two types of hyperplasia: usual hyperplasia and atypical hyperplasia. In usual hyperplasia, breast cells appear normal, while in atypical hyperplasia, the cells look abnormal. Women with atypical hyperplasia have a higher risk of breast cancer than women with usual hyperplasia. For more information, you can visit the Risk Factors section on komen.org.

Studies show women with a higher birthweight (meaning they weighed more at birth) appear to have an increased risk of breast cancer, especially before menopause. While it doesn’t appear to be linked to higher estrogen levels as an adult, higher birthweight may be a marker for other growth-related factors that affect breast cancer risk. Researchers are still studying the link between birthweight and breast cancer risk.

Being exposed to high levels of radiation early in life can increase the risk of breast cancer. Women who were treated with radiation for Hodgkin’s disease at a young age and are also at increased risk. In general, the greater the radiation exposure and the younger the age when exposed, the higher the risk.

High bone density can also increase breast cancer risk. It can indicate high estrogen levels in the body. The more estrogen a woman produces in her lifetime, the more bone mass she has, and higher estrogen levels are linked to an increased risk of breast cancer.

Ductal carcinoma in situ, or DCIS, is a non-invasive breast cancer that may progress to invasive breast cancer if left untreated. Because health care providers can’t predict which cases of DCIS will progress to invasive breast cancer, almost every case is treated. For more information, you can visit the Risk Factors section on komen.org.