Atypical Hyperplasia

This information will help you understand what atypical hyperplasia is, what it means for your risk of developing breast cancer, and what screening and prevention strategies may be right for you.

What does hyperplasia mean?

The breast is made of small round sacs that produce milk, called lobules, and ducts, which carry milk from the lobules to your nipples. Normally, the lobules and ducts are lined by 2 layers of cells. When there are more cells than usual, it’s called hyperplasia. If the growth of the extra cells looks like the normal breast pattern under the microscope, the hyperplasia will be called usual. If the growth patterns of extra cells look more abnormal, they will be called atypical hyperplasia.
The 2 major types of hyperplasia in the breast are ductal hyperplasia and lobular hyperplasia.

Atypical Ductal Hyperplasia (ADH)

ADH means that some of the cells in the breast grow in an abnormal pattern.  Under the microscope ADH shares some, but not all of the features of ductal carcinoma in-situ (which is a pre-cancer). This means that ADH is not yet a pre-cancer, although it is linked to an increased risk of getting breast cancer later on. If ADH is found after a needle biopsy, you may need surgery to be sure that there is not a small breast cancer also present in your breast.  If nothing more serious than ADH is seen after the surgery, your doctor will talk with you about the screening recommendations that are best for you and strategies to reduce your risk of developing breast cancer in the future.

Atypical Lobular Hyperplasia (ALH)

ALH is an abnormal appearing growth of cells within the lobules of the breast that is linked to an increased risk of getting breast cancer.  When ALH is found after a needle biopsy, additional surgery is not always necessary. You and your doctor will decide whether surgery is right for you.

Breast Cancer Screening

Women with atypical hyperplasia (either ADH or ALH) should have regular breast exams and breast imaging.  You and your doctor will decide what type of breast imaging is best for you, based on your personal history as well as your breast density.  At Memorial Sloan Kettering, we recommend a physical exam with a breast specialist and breast imaging every year.
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How to Lower Your Risk for Invasive Breast Cancer


Taking certain medications to help lower your risk of developing breast cancer is known as chemoprevention. Chemoprevention for breast cancer means taking a pill once a day for 5 years.  Studies have shown that these mediations may lower your risk of breast cancer by more than 50%.  Talk to your healthcare provider about the risks and benefits of these options so you choose the one that is best for you.

Tamoxifen and raloxifene  

Tamoxifen and raloxifene are medications that lower the risk of breast cancer by blocking the effects of estrogen, a hormone that influences the development of many breast tumors. These medications only reduce your risk of estrogen receptor-positive breast cancer, which is the most common type. They will not reduce your risk of estrogen receptor-negative cancers.   You can take raloxifene only if you have already gone through menopause. You can take tamoxifen before or after menopause. 

Aromatase inhibitors  

Aromatase inhibitors are medications that stop a key enzyme (called aromatase) from changing other hormones into estrogen. Aromatase inhibitors are part of the standard treatment for breast cancer in women who have gone through menopause. One of these medications, exemestane, has also been shown to lower the risk of breast cancer in postmenopausal women at higher risk, including women with atypical hyperplasia.

Prophylactic mastectomy

Bilateral prophylactic (PRO-fih-LAK-tik) mastectomy is the surgical removal of both breasts to try to prevent breast cancer.  This surgery is seldom used to lower the risk of breast cancer in women with ADH or ALH.
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