Unsupervised hierarchical clustering of the Stockholm cohort (n = 159) using the 64-gene set. Each column refers to a patient and each row to a gene. Red indicates a high value of gene expression, and green indicates a low value. The list of genes is presented in Additional file 1, in the same order as they appear on the plot. Risk.score, computed by linear discriminant analysis and used here only to describe the clusters. Status.5 yr, black if the corresponding patient had distant metastasis or died within 5 years. BRCA.5 yr, black if the death was due to breast cancer. NodePos, black if the corresponding patient was lymph-node-positive; Grade3, black if the patient had Elston grade 3.