Luminal A are the most prevalent type of BC (58.5%) and are ER+/PR+/HER2− and Ki-67low; Luminal B account for around 14% of BC and are ER+/PR+/HER2− and Ki-67high; HER2-positive BC represent 11.5% of BC and are ER−/PR−/HER2+. The gene discussed is ESR1; the disease is breast cancer.