In comparison to their older counterparts, those under forty had a higher tumour grade (p = 0.044) and stage (p = 0.046), a lower incidence of lobular tumours (p < 0.001), higher estrogen receptor negativity (p < 0.001) and higher HER2 over-expression (p = 0.002); there was no statistical difference as regards tumour size (p = 0.477). This evidence concerns the gene ESR1 and neoplasm.