Atypical hyperplasia of the breast

Hyperplasia is an increase in the number of normal cells growing in a tissue. Atypical hyperplasia means that the cells that are increasing in a tissue are abnormal.

Atypical ductal hyperplasia is an increase in abnormal cells growing in the breast ducts. It is the most common type of atypical hyperplasia of the breast.

Atypical lobular hyperplasia is an increase in abnormal cells growing in the groups of glands that make milk (called the lobules).

Atypical hyperplasia and breast cancer

Having atypical hyperplasia increases the risk for breast cancer. This risk is even higher in women who have a family history of breast cancer or who are diagnosed with atypical hyperplasia before they reach menopause. Breast cancer is more likely to start in the breast where atypical hyperplasia is found. The risk of developing breast cancer is greatest 10–15 years after atypical hyperplasia is diagnosed. The risk begins to go down after 15 years.

Women with atypical hyperplasia should talk to their doctor about a personal plan of testing for breast cancer, including regular mammography.


Atypical hyperplasia of the breast does not cause any symptoms. It is usually found during screening mammography.


You may be offered chemoprevention if you have atypical hyperplasia of the breast, especially if you have a family history of breast cancer. The drugs used are called selective estrogen-receptor modulators (SERMs) because they block the effects of estrogen in breast tissue:

  • Tamoxifen (Nolvadex, Tamofen) is given to premenopausal and post-menopausal women.
  • Raloxifene (Evista) is only given to post-menopausal women.

Women with atypical hyperplasia should talk to their healthcare team about the benefits and possible risks of taking SERMs to reduce their risk of breast cancer.

Expert review and references

  • American Cancer Society. Breast Cancer. 2015:
  • American Cancer Society . Non-Cancerous Breast Conditions . 2015 :
  • Guray M, & Sahin AA . Benign breast diseases: classification, diagnosis, and management. Oncologist. AlphaMed Press; 2006.
  • Kiluk JV, Acs G, & Hoover SJ . High-risk benign breast lesions: current strategies in management. Cancer Control: Journal of the Moffitt Cancer Center. H. Lee Moffitt Cancer Center & Research Institute; 2007.
  • Morrow M, Burstein HJ, and Harris JR . Malignant tumors of the breast. DeVita VT Jr, Lawrence TS, & Rosenberg SA. Cancer: Principles and Practice of Oncology. 10th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2015: 79: 1117-1156.

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