PGR and breast cancer: Among luminal A (ER/PR+, HER2/neu-), luminal B (ER/PR+, HER2/neu+), HER2 overexpression (ER-, PR-, HER2/neu+) and triple negative subtypes of breast cancer, the CD24-CD44+ percentage was only significantly increased in triple negative breast cancer when compared with luminal B (P = 0.0464; see Figure S5B in Additional file 1).