Freya R. Schnabel, MD, Professor of Surgery, NYU School of Medicine, summarizes information presented at the 2011 San Antonio Breast Cancer Symposium that discussed the risk of developing breast cancer in women with atypical lesions.

Atypical ductal and lobular hyperplasia and lobular carcinoma in situ are risk factors for developing breast cancer. The degree of risk varies depending on the atypia type.

All varieties of lesions increased a women's risk for breast by similar amounts. On average cancer began developing 4 years after the lesions were detected, the 10-year cancer risk varied from 14% to 20%. Additionally, the majority of cancers occurred ipsilaterally for all atypia types combined.

This information challenges previously held assumptions on breast cancer risk factors. It was previously believed that cancer should develop equally without regards to laterality. However, the data suggests that more cancer developed in the same breast as the lesions than contralateral.