Abstract: The disclosure includes the use of gene expression profiles, or patterns, with clinical relevance to breast cancer. In particular, the disclosure provides the identities of genes that are expressed in correlation with the presence of breast cancer, the grade of breast cancer, and the type of breast cancer. The disclosed methods assist in the detection and identification of breast cancer in a patient and so helps determine treatment and clinical outcome, and so prognosis, for the patient. The gene expression levels, whether embodied in nucleic acid expression, protein expression, or other expression formats, may be used detect the presence of in situ or invasive breast cancer.