The diagnosis of breast cancer is morphologically based. Pathologic parameters, such as tumor size, lymph node status, and histological grade are well accepted to guide treatment decisions in clinical practice. Estrogen receptor, progesterone receptor and HER2 status are also routinely assessed in today's pathology laboratories to provide further information on predictive and prognostic factors affecting patients' care. Newer molecular techniques, including gene-expression profiling have been widely used to study breast cancer and several molecular prognostic tests already available for clinical use stemmed from these scientific efforts. Authors review prognostically important aspects of the diagnostic pathology and the molecular classification of invasive breast cancer.