These subtypes are grouped into four categories according to the immunohistochemical expression of hormone receptors, such as progesterone receptor-positive (PR+), estrogen receptor-positive (ER+), human epidermal growth factor receptor-positive (HER2+), and triple-negative breast cancer (TNBC), which are characterized by the absence of expression of any of the above receptors2. This evidence concerns the gene ESR1 and triple-negative breast carcinoma.