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Adenosis is a benign (non-cancerous) breast condition in which the lobules (milk-producing glands) are enlarged, and there are more glands than usual. Adenosis is often found in biopsy samples of women who have fibrocystic changes in their breasts.
There are many other names for this condition, including aggregate adenosis, tumoral adenosis, or adenosis tumor. Even though some of these terms contain the term tumor, adenosis is not breast cancer.
Sclerosing adenosis is a special type of adenosis in which the enlarged lobules are distorted by scar-like tissue. This type may cause breast pain.
If many enlarged lobules are close to one another, they may be large enough to be felt as a breast lump. In cases like this, a breast exam may not be enough to tell if the lump is adenosis or something else (such as breast cancer).
Calcifications (mineral deposits) can form in adenosis (including sclerosing adenosis), as well as in breast cancers. These can show up on mammograms, which can make it hard to tell these conditions apart.
Because of these uncertainties, a breast biopsy is usually needed to know if the breast change is caused by adenosis or cancer. (In a biopsy, small pieces of breast tissue are removed and checked under a microscope.)
Adenosis doesn't usually need to be treated, unless it's causing bothersome symptoms.
Most types of adenosis are not thought to increase breast cancer risk, although some studies have found that women with sclerosing adenosis have a slightly higher risk of breast cancer.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
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Last Revised: January 25, 2022
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