Updated CV, FTP location and Modification list. Human breast cancer tissue samples from 18 patients with high-risk or low-risk MammaPrint breast cancer were analyzed. The membrane fractions were enriched, and the extracted proteins were reduced, alkylated, digested with Lys-C and Trypsin, and labelled with iTRAQ4plex: 114; high risk; 115; low risk. Identification results were filtered at 1% false discovery rate (FDR) thresholds by searching against a randomized decoy database using Mascot at peptide and protein levels.