ESR1 and breast cancer: In human breast cancer and canine mammary carcinoma, several studies have shown that IGF1R expression parallels ER expression [18, 20, 39, 41], but we found that IGF1R overexpression was correlated with the negativity for ER and PR in the total cohort as Law et al. showed for phosphorylated IGF1R/IR expression in human breast cancer [45].