Our goal was to investigate the intratumoral heterogeneity of proteins with clinical relevance to breast cancer, either predictive markers for therapies targeting HER2 [2] or prognostic markers including HER2, estrogen and progesterone receptors [1], E-Cadherin [3], and uPA and PAI-1 [4], [5]. The gene discussed is PGR; the disease is breast carcinoma.