Utilizing serial analysis of gene expression (SAGE) databases that are publicly available from the Cancer Genome Anatomy Project website http://cgap.nci.nih.gov, the expression of selected S100 genes were compared between normal and cancer breast libraries. Confirming classical laboratory methods, SAGE found the expression of S100A2 to be higher in normal tissue than in cancer tissue, as well as S100A4 being found higher in cancer tissue than in normal breast tissue. S100A7 is one of the highest expressed genes in some ductal carcinoma in situ libraries, compared with normal breast tissue where expression is almost undetectable. S100A15, which resulted from a gene duplication of S100A7, is not expressed at the same level as S100A7 in breast cancer. SAGE allows the identification and confirmation of individual gene expression levels between normal tissues and cancer tissues of the breast.