Breast cancer prognosis is currently stratified into eight groups based on anatomic characters, including T (tumor), N (nodes), M (metastasis), and biological types, including estrogen/progesterone receptor, and HER2 (Human Epidermal Growth Factor Receptor 2) status according to American Joint Committee on Cancer (AJCC) 8th edition.26 Furthermore, categorization based on genome, RNA, or protein expression profiles are also applied.26 Such complex stratifications require large number of breast cancer cases for testing of prognosis difference across each subgroup. This evidence concerns the gene PGR and breast cancer.