The breast contains milk ducts (small tubes that carry milk) and lobules (glands that make milk). These structures are normally lined by 1 or 2 layers of healthy cells that look the same or similar under a microscope.
In a condition called hyperplasia, these cells grow very quickly and there are too many normal cells. The cells start to build up in the milk ducts and lobules of the breast.
Sometimes these cells begin to change and no longer look the same. When this happens, the cells are called
atypical (meaning not typical).
Atypical hyperplasia describes a condition when these cells change and look abnormal under a microscope. The image below shows how the cells can change over time, becoming more abnormal in size, shape, and appearance.
There are 2 kinds of atypical hyperplasia:
- Atypical ductal hyperplasia is found in the ducts of the breast.
- Atypical lobular hyperplasia is found in the lobules of the breast.
If you have 1 of these conditions, it doesn’t mean you have cancer. It can take many years for atypical cells to become breast cancer. But you are at higher risk for developing breast cancer.
Breast cancer cells start as non-invasive (also called in situ). But when they are left undiagnosed or untreated, these cells can invade the surrounding tissues and spread (become invasive or metastatic).
Many people may not know they have atypical hyperplasia. These changes do not show up on a regular screening mammogram, and you can’t feel them during a breast self-exam. Atypical hyperplasia is commonly found during a breast biopsy done to investigate an abnormal mammogram, a breast lump, nipple discharge, or another breast concern.
If you know you have atypical hyperplasia, talk with your healthcare provider about a treatment and follow-up plan based on your individual risk factors.
