ESR1 and neoplasm: Comparing these four groups within the whole unselected series (i.e. ER+ and ER- patient samples) for clinico-pathological parameters, breast cancer molecular subtype, and molecular biomarker expression revealed statistically significant differences between the four groups with respect to tumor grade, mitotic scores, nuclear pleomorphism, tubule formation, Nottingham Prognostic Index (NPI), lympho-vascular invasion (LVI) and histologic tumor types (Table 2).