An Overview of Adenosis of the Breast

Adenosis is a benign condition of enlarged breast lobules

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

Adenosis may show up on a mammogram as a mass or calcification (small white calcium deposits), which are typically signs of breast cancer. Adenosis in the breast is also called mammary adenosis, aggregate adenosis, tumoral adenosis, or adenosis tumor. Despite the term "tumor," this condition is benign (non-cancerous). Some research indicates that adenosis may offer some increased risk for breast cancer.

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


Adenosis may not be detectable during a breast self-exam or a clinical breast exam, because it may be small and not near the skin. But when adenosis occurs in several lobules in a group, you may feel a lumpy area. This kind of lump 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: However, sometimes both breasts may be affected. The lump is usually painless. While the lumps are usually small, some can be felt. They may have a nodular appearance (mass-like).

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


Researchers do not know what exactly causes adenosis. However, researchers speculate that adenosis lumps may be caused by normal hormonal influences and fluctuations and certain gene mutations. There is not enough research to back these theories up.

Risk factors for adenosis are not understood either. Risk factors for all types of benign breast tumors include:

  • Being female as women have a higher risk than men
  • Being overweight
  • Alcohol consumption
  • Starting your menstrual cycle prior to age 12
  • Post-menopausal hormone therapy
  • 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

Having certain risk factors does not mean you will develop adenosis. It just means that risk factors increase your chance of getting the condition compared to someone without the same risk factors. And not having risk factors does not guarantee you will not get the condition. 

Your doctor is in the best position to answer the effect that risk factors may have on your health and the potential to develop a particular condition. 


Detecting adenosis with a physical exam is usually not a enough to confirm a diagnosis even if the lump is large. A clinical breast exam won't give you a conclusive diagnosis because this kind of lump feels similar to a hard tumor. If your doctor is concerned about the lump, breast cancers, or the possibility of other breast problems, he or she will ask for imaging testing, including mammograms and ultrasounds. 

Breast adenosis can show up on a mammogram, but because it can be associated with calcifications, like a cancerous tumor, it cannot be distinguished from cancer by doing a visual exam.

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 use ibuprofen. For some women, avoiding caffeine in drinks and chocolate reduces swelling and pain. If none of these strategies bring you relief from breast discomfort, talk your doctor about additional ways to manage pain and discomfort.

Breast Cancer Risk

If you are diagnosed with sclerosing adenosis, you do have an increased risk of developing breast cancer. One 2014 large cohort study showed that adenosis was found in 28 percent of benign biopsies as a single feature without breast cancer. 

The researchers also noted that adenosis-specifically sclerosing adenosis-did double the risk for breast cancer for women who had risk factors, such as age and family history. Moreover, adenosis might be associated with the later development of breast cancer.

A Word From Verywell

Being aware of of adenosis and risk factors for breast cancer may offer a prediction method for women with benign breast conditions. And if a woman eventually develops breast cancer, it can be diagnosed and treated early and successfully.

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