An Overview of Adenosis of the Breast

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Adenosis is a benign breast condition that occurs in the lobules (milk-producing glands), causing them to become enlarged. There are also more glands than normal. Adenosis may cause a lump, or multiple lumps, that can be felt. If enlarged lobules are also being distorted, or pulled out of shape, by scar-like fibrous tissue, the condition is more specifically referred to as sclerosing adenosis.

Adenosis may show up on a mammogram as a mass or calcification (small white calcium deposits), both of which are typically signs of breast cancer. But though some research indicates that adenosis (specifically, the sclerosing type) may offer some increased risk for breast cancer, the condition itself is not cancerous.

Adenosis lumps mostly affect premenopausal women and may not necessarily require treatment. 

Also Known As

Adenosis in the breast is also called mammary adenosis, aggregate adenosis, tumoral adenosis, or adenosis tumor.


Adenosis may not be detectable during a breast self-exam or a clinical breast exam, because it may be small and not near the surface of the skin. Adenosis is more likely to be detected in these ways when it yields several lobules in a group. To the touch, this lumpy area can feel like a cyst, fibroadenoma, or even a tumor.

The most general characteristics of adenosis are:

  • Periodic pain and swelling in the breast(s): The pain is either bursting or pulling. Level and frequency may increase with your menstrual cycle. 
  • Breast engorgement: This symptom also seems to increase during a women’s menstrual cycle.
  • A benign lump in a single breast: The lump is usually painless and, while typically small, may be felt. It may have a nodular (mass-like) appearance. Sometimes, lumps may occur in both breasts.

Adenosis does not change the skin or shape of the breast. It also does not affect lymph nodes, which are usually not enlarged and appear to function normally.  

woman speaking to her doctor
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Researchers do not know what exactly causes adenosis. However, in 2009, researchers speculated that adenosis lumps may be caused by normal hormonal influences and fluctuations, as well as certain gene mutations. More research is needed.

Risk factors for adenosis are not understood either. Risk factors for benign breast conditions in general include:

  • Being female
  • Being overweight
  • Alcohol consumption
  • Starting your menstrual cycle prior to age 12
  • Use of post-menopausal hormone therapy
  • Use of birth control pills
  • Having your first child after age 35 or never having a child
  • Not breastfeeding if you have had a child
  • Physical inactivity

While these increase your chance of developing adenosis or another benign breast condition, they do not guarantee that you will. Likewise, you may be diagnosed even if you don't have any (or many) of these risk factors.


Given that adenosis can feel similar to other lumps, detecting the condition with a physical exam is usually not enough to confirm a diagnosis—even if the lump is large.

If your doctor is concerned about the possibility of breast cancer or another breast problem, they will ask for imaging tests, including a mammogram and ultrasound. Breast adenosis can show up on a mammogram, but because it can be associated with calcifications, it cannot be distinguished from cancer with this test alone.

A biopsy is usually the best way confirm a diagnosis of adenosis. To perform the biopsy, you will be given local anesthetic so the doctor can remove of a sample of the lump and send it to a laboratory for testing. 


Because adenosis is a benign condition, no treatment is necessary. If it becomes painful, you might try wearing a bra with good support or taking ibuprofen. For some women, avoiding caffeine in drinks and chocolate reduces swelling and pain.

If none of these strategies ease your breast discomfort, talk your doctor about additional ways to manage your pain.


If you are diagnosed with sclerosing adenosis, your doctor will likely recommend a schedule for routine screening for breast cancer, given your increased risk due to your condition.

One 2014 large cohort study noted that sclerosing adenosis doubled the risk of breast cancer in women who also had certain risk factors, such as increased age and family history. Moreover, adenosis might be associated with the later development of breast cancer.

The researchers also reported that adenosis was found in 28% of benign biopsies as a single feature—without breast cancer. 

A Word From Verywell

Finding a lump (or any change) in your breast can immediately make your mind jump to breast cancer. Learning more about adenosis and other conditions that can mimic breast cancer can help you get a better sense of the possibilities and temper runaway concerns while you wait to see your doctor.

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  1. American Cancer Society. Adenosis of the Breast. Updated September 10, 2019.

  2. Visscher DW, Nassar A, Degnim AC, et al. Sclerosing adenosis and risk of breast cancer. Breast Cancer Res Treat. 2014;144(1):205-12. doi:10.1007/s10549-014-2862-5

  3. American Academy of Family Physicians. Benign Breast Conditions. Updated September 17, 2019.

  4. Worsham MJ, Raju U, Lu M, et al. Risk factors for breast cancer from benign breast disease in a diverse population. Breast Cancer Res Treat. 2009;118(1):1-7. doi:10.1007/s10549-008-0198-8