ESR1 and obesity disorder: Moreover, another study evaluated the association between obesity and breast tumor risk, analyzing the women enrolled in the multinational European Prospective Investigation into Cancer and Nutrition (EPIC) prospective study (n = 27,012) in relation to tumor subtypes according to the expression of clinically used markers (Estrogen receptor, ER, Progesterone Receptor, PR, HER2, Ki67, Bcl-2 and p53).