PGR and invasive ductal breast carcinoma: Merkin et al. studied 164 cases of breast cancer patients, including 149 cases of invasive ductal carcinoma and 15 cases of invasive lobular carcinoma [three patients could not be sure of whom the triple-negative state, negative for the estrogen receptor (ER)/progesterone receptor (PR)/human epidermal growth factor receptor-2 (HER2)].