Breast cancer can be classified based on molecular markers such as estrogen receptors, progesterone receptors, and human epidermal growth factor 2 into three major subtypes: hormone receptor-positive/HER2-negative (accounting for approximately 70%), HER2-positive (comprising 15%–20%), and triple-negative (lacking all three standard molecular markers, representing 15%). The gene discussed is PGR; the disease is breast cancer.