Study design and sample description

The discovery cohort comprises twenty-six FFPE samples from patients diagnosed of triple negative breast cancer (TNBC) were retrieved from I+12 Biobank (RD09/0076/00118) and from IdiPAZ Biobank (RD09/0076/00073), both integrated in the Spanish Hospital Biobank Network (RetBioH; www.redbiobancos.es) between 1997 and 2004. The targeted proteomics cohort includes one hundred and fourteen samples from patients diagnosed of triple negative breast cancer were retrieved from I+12 Biobank (RD09/0076/00118) and from IdiPAZ Biobank (RD09/0076/00073), both integrated in the Spanish Hospital Biobank Network (RetBioH; www.redbiobancos.es) between 1997 and 2012. Sixty samples from I+12 Biobank were previously included in an analytical observational case–control study [14]. The histopathological features of each sample were reviewed by an experienced pathologist to confirm diagnosis and tumor content. Eligible samples had to include at least 50% of tumor cells.