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Adenosis of the Breast
Adenosis is a benign (noncancerous) breast condition in which the lobules (milk-producing glands) are enlarged, and there are more glands than usual. Adenosis is often found in breast biopsy samples of women who have fibrocystic changes in their breasts.
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.
Diagnosis of breast adenosis
If many enlarged lobules are close to one another, they may be large enough to be felt as a breast lump. A breast exam may not be enough to tell if the lump is adenosis or something else, such as breast cancer.
Calcifications, which are small deposits of calcium, can form in adenosis as well as in breast cancers. These can be seen on mammograms, which can make it hard to tell these conditions apart.
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.
Does adenosis need to be treated?
Adenosis doesn't usually need to be treated, unless it's causing bothersome symptoms. If needed, it can be removed with surgery.
How does adenosis affect breast cancer risk?
Most types of adenosis are not thought to increase breast cancer risk, although sclerosing adenosis seems to increase risk slightly.
Because of this, breast cancer screening recommendations aren’t usually different if adenosis is found.
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- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
Collins LC, Schnitt SJ. Chapter 9: Pathology of benign breast disorders. In: Harris JR, Lippman ME, Morrow M, Osborne CK, eds. Diseases of the Breast. 5th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2014.
Orr B, Kelley JL. Benign breast diseases: Evaluation and management. Clin Obstet Gynecol. 2016;59(4):710-726.
Sabel MS. Overview of benign breast diseases. UpToDate. 2026. Accessed at https://www.uptodate.com/contents/overview-of-benign-breast-diseases on March 10, 2026.
Visscher DW, Nassar A, Degnim AC, et al. Sclerosing adenosis and risk of breast cancer. Breast Cancer Res Treat. 2014;144:205-212.
Last Revised: May 26, 2026
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