Women with neurofibromatosis 1 are at a moderately increased risk of developing breast cancer and should be considered for early screening

Background: Malignancy risks in neurofibromatosis 1 (NF1) patients are elevated but those occurring outside of the nervous system have not been clearly defined. We evaluated the risk of breast cancer in women with NF1 in a population-based study. Methods: The risk of breast cancer in a cohort of 304 NF1 women aged ≥20 years was assessed and compared to population risks over the period 1975-2005 using a person years at risk analysis. Results: There were 14 breast cancers in the follow up period yielding a Standard Incidence Ratio (SIR) of 3.5 (95% CI 1.9-5.9). However, 6 breast cancers occurred in the forties and the SIR of breast cancer aged <50 years was 4.9 (95% CI 2.4-8.8). Interpretation: Women with NF1 have a five-fold risk of breast cancer <50 years of age, are in the moderate risk category and should be considered for mammography from 40 years of age.