Breast cancers of basal phenotype have been identified by molecular profiling and are associated with a poor prognosis. This review describes the morphological characteristics of these tumors and focuses on their profiling using immunohistochemistry: absence of detectable hormone receptors and HER2, expression of basal cytokeratins (CK5/6, CK14), myoepithelial markers (p63, smooth muscle actin) and HER1. This phenotype may be encountered in all histological types of breast cancer and is further divided into three subtypes according to prognosis and protein profiling. Pure basal and basal/myoepithelial subtypes have a poor prognosis in contrast to the myoepithelial subtype.