58/3672 NF1‐patients (1.6%) were diagnosed with breast cancer during study period. A total of 25 patients were <50 years old and 33 pt were >50 years old. Relative risks were highest for women aged 30–39 (RR 6.5 95% CI 2.6–13.5), and declined with increasing age (60–69 RR 1.9 95% CI 1.0–3.3) This evidence concerns the gene NF1 and breast carcinoma.