Table 6

 Probability of breast cancer cases related to BRCA1 germline mutations for different groups of patients with breast cancer, on the basis of a combination of classical features: age at diagnosis and MAI

ClassificationDecision treeNumber of sporadic casesNumber of cases with BRCA1 mutationsProbability of BRCA1-related disease (%)Number of intermediate-risk casesNumber of high-risk casesNumber of cases with BRCA2 mutations
MAI, mitotic activity index.
SporadicAge ⩾54 years and MAI<17269002141
IntermediateAge ⩾54 years and MAI⩾1712522512
IntermediateAge <54 years and MAI<17185222222
BRCA1 relatedAge <54 years and MAI⩾179156311120