Your breast biopsy is back and you were told it showed “atypical hyperplasia”. Questions come to your mind such as: What does this mean? Do I need surgery? How does this affect my breast cancer risk?

What is atypical hyperplasia?

Atypical hyperplasia (or atypia) means that there are abnormal cells in the breast tissue that was biopsied. These are high-risk lesions (spots), but are benign (not cancer). These findings account for 10 percent of benign breast biopsies. There are two types of atypical hyperplasia – atypical ductal hyperplasia (ADH) and atypical lobular hyperplasia (ALH). Atypical ductal hyperplasia means that abnormal cells are located in a breast duct. Atypical lobular hyperplasia means that abnormal cells are in a breast lobule (the milk-making parts of the breast). Another high-risk lesion is lobular carcinoma in situ (LCIS), which is more extensive involvement of atypical cells in the breast lobules.

What does having atypical hyperplasia mean?

Cells of this type on a breast biopsy do not mean cancer. They are a marker for increased breast cancer risk. Studies have shown that women with atypical hyperplasia have up to a four times increase in breast cancer risk, especially estrogen receptor-positive breast cancer.

Long-term data have shown that the younger a woman is at the time of her diagnosis of atypical hyperplasia, the more likely she is to develop breast cancer later in life. Specifically, five years after the diagnosis of atypical hyperplasia, seven percent of women will develop breast cancer. Ten years after the diagnosis, thirteen percent of women will develop cancer, and 25 years after the diagnosis, 30 percent of women will develop breast cancer.

What is estrogen receptor-positive breast cancer?

Most breast cancer cells respond to hormones, specifically estrogen or progesterone. These hormones circulate in the blood. The cancer is called estrogen receptor positive if it responds to estrogen. This means that estrogen triggers the cancer to grow. Progesterone receptor-positive breast cancer means that progesterone triggers the cancer to grow.

Knowing which hormone the breast cancer responds to helps determine how to best treat or prevent breast cancer. One study showed that of the women who did develop breast cancer, 88 percent of the breast cancers were estrogen receptor positive.

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