Atypical hyperplasia (AH) and lobular carcinoma in situ (LCIS) are markers for an increased risk of breast cancer, yet outcomes for these diagnoses are not well-documented. In this study, all breast biopsies performed for radiologic abnormalities over a 10-year period were reviewed. Patients with AH or LCIS were followed for an additional 10 years to assess subsequent rates of cancer diagnosis. Long-term follow-up showed that 25 (7.8%) patients with AH and 5 patients with LCIS (5.7%) developed breast cancer over the follow-up period, a lower rate of breast cancer development than predicted by risk models.