PGR and breast carcinoma: While 70% of human breast carcinomas fall into luminal CD44-/CD24+ subtypes, which are estrogen receptor alpha (ERa) positive and are initially sensitive to endocrine therapy [4], triple negative breast carcinomas (TNBCs) show a basal-like CD44+/CD24- phenotype and low/absent levels of expression of ERα, progesterone receptor (PR) and HER2 tyrosine kinase receptor [5].