What is atypical hyperplasia?

What is atypical hyperplasia?

Atypical hyperplasia (or atypia) means that there are abnormal cells in breast tissue taken during a biopsy. (A biopsy means that tissue was removed from the body for examination in a laboratory.) These abnormal cell collections are benign (not cancer), but are high-risk for cancer.

Findings of atypical hyperplasia account for 10% 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.