In clinical practice, preoperative core needle biopsy (CNB) is the standard procedure for breast cancer diagnosis and neoadjuvant regimen decision [10,11] due to its high accuracy similar to that of surgical excision specimen (SES) samples in histology and estrogen receptor (ER), progesterone receptor (PR) and HER2 status determination [12,13]. The gene discussed is ESR1; the disease is breast cancer.