PGR and breast cancer: Nevertheless, surrogate classification of BC into intrinsic subtypes (luminal A-like, luminal B-like (HER2-negative), luminal B-like (HER2-positive), HER2-positive (non-luminal) and triple-negative) based on immunohistochemical/in situ hybridization methods for the evaluation of hormone receptors (estrogen and progesterone receptors (ER, PR)), human epidermal growth factor 2 (HER2), and proliferation factor Ki-67 is a commonplace practice [3,[8], [9], [10]] providing not only prognostic but also predictive information [9,[11], [12], [13], [14]].