PGR and breast cancer: Basal-like breast cancers are characterized by the lack of ER, PR and ERB-B2 expression and cytokeratin 5/6 and/or epidermal growth factor receptor expression [7], whereas the luminal-like subtype is characterized by ER or PR expression [7] and further subgrouped into luminal A or B depending on the absence or presence of ERB-B2 expression [10].