PGR and breast cancer: This type of tumor shows a high grade of variability and based on molecular and histological characteristics, different types of BC can be identified: BC positive for both estrogen and progesterone receptors (ER+, PR+), named Luminal A, BC positive for ER, PR and for human epidermal receptor 2 (HER2+) (named Luminal B), BC positive only for HER2 (named HER2-overexpression) and triple-negative BC (TNBC, negative for ER, PR, and HER2 receptors), also called Basal-like [3,4].