ESR1 and neoplasm: There were no statistically significant differences between the training and validation groups in terms of age, menopausal status, history of breastfeeding, family history of cancer, underlying disease, tumor pathology type, tumor molecular subtypes, TNM stage (T stage [1–4], N stage [0–3]), ER status, PR status, HER-2 status, Ki-67 expression, tumor location, CEA levels, CA153, CA125, CA50 levels, pCR, or non-pCR (Table 1).