PGR and breast cancer: However, some primary tumors selectively target the liver as a metastatic location, according to the “seed-and-soil” hypothesis [2]; examples are patients with uveal melanoma with a loss of chromosome 3 [3], and patients with breast cancer with the human growth factor receptor 2 (HER-2) positivity in combination with estrogen (ER) and progesterone receptor (PR) positivity [4].