BRCA1 and maternal uniparental disomy of chromosome 20: Because several studies have shown a higher incidence of MBCs in young patients, in particular in a BRCA1 context, we compared the ages of the two groups of patients (MBC group: median 53.5 years; range 34 to 76 years; BLC group: median 60 years; range 37 to 82 years; Table 1).