Atypia on Breast Biopsy: What Does It Mean?

Breasts are composed of lobules, which make milk, and ducts, which carry the milk to the nipple. The lobules and ducts are both lined by two layers of cells. When the cells lining the lobules or ducts grow, the collection of cells is called hyperplasia. Usual hyperplasia poses no risk, but when the cells grow in an irregular pattern they can become problematic. This irregular pattern is known as atypia. Atypical cells are not cancerous, but will increase a patient’s risk for developing cancer in their lifetime.

Atypical ductal hyperplasia, also known as ADH, involves the ducts of the breast tissue and atypical lobular hyperplasia, also known as ALH, involves the lobules of the breast tissue. When either ADH or ALH are seen by the pathologist on a core needle biopsy performed for an abnormal mammogram or ultrasound, an open surgical biopsy may be recommended. The reason for this recommendation is that core needle biopsy samples can potentially miss a breast cancer 10-20% of the time. Atypia found on an open surgical biopsy does not require another operation but will be helpful in assessing for cancer and in calculating a patient’s risk for developing breast cancer in the future.

Other forms of abnormal cells include lobular neoplasia, also called LIN, and lobular carcinoma in-situ, as called LCIS. ADH and ALH will increase a patient’s risk of developing breast cancer by 4 fold, and LIN and LCIS will lead to 10 times the risk of developing breast cancer. For those individuals who have an elevated risk of getting breast cancer, additional enhanced screening with breast MRI and medication such as Tamoxifen, Anastrozole (Arimidex) or Evista (Raloxifene) to reduce breast cancer risk may be considered.

By knowing your pathology results from your breast biopsies, you can understand your risk of developing breast cancer and participate in creating a follow-up plan that is best for you.