Young age at breast cancer diagnosis has been associated with increased risk of recurrence and mortality. We reevaluated this assumption in a large, modern cohort of women diagnosed with breast cancer at age aecurrency sign40 years. We identified women with breast cancer at age aecurrency sign40 years at a single institution from 1996-2008. We assessed locoregional recurrence (LRR), distant recurrence, disease-free survival (DFS), and overall survival (OS), and correlated patient and tumor characteristics with outcomes. We identified 584 women aged aecurrency sign40 years with breast cancer. Median age was 37 years, and median follow-up was 124 months; 61.5 % were stages 0-I and 38.5 % were stages II-III. Overall, 57.4 % had lumpectomies and 42.5 % mastectomies. DFS was 93 % at 5 years and 84.5 % at 10 years. OS was 93 % at 5 years and 86.5 % at 10 years. On multivariate analysis, worse DFS was associated with positive nodes (p = 0.002); worse OS was associated with larger tumor size (p = 0.042). When stratified by lumpectomy versus mastectomy, there were no significant differences in survival or recurrence. For lumpectomy patients, DFS was 96 % at 5 years and 88 % at 10 years; OS was 96 % at 5 years and 89 % at 10 years. For mastectomy patients, DFS was 89.5 % at 5 years and 79 % at 10 years; OS was 90 % at 5 years and 83 % at 10 years. Lumpectomy LRR rates were 1 % at 5 years and 4 % at 10 years. Mastectomy LRR rates were 3.5 % at 5 years and 8.7 % at 10 years. Outcomes for women with breast cancer at age aecurrency sign40 years have improved. Lumpectomy recurrence rates are low, suggesting that lumpectomy is oncologically safe for young breast cancer patients.