ESR1 and cancer: A previous study by Chavez–MacGregor et al. from University of Texas MD Anderson Cancer Center (MDACC) developed a risk score staging system based on a risk score of 0–3 assigned according to the histological grade (0 point for G1-2, 1 point for G3), ER status (0 point if ER-positive, 1 point if ER-negative), and HER2 status (0 point if HER2-positive, 1 point if HER2-negative) to stratify the prognosis of patients (Table 3)18.