Baseline characteristics in cases and controls.

Features of primary tumors of cases and controls. Number (%), Mean (± standard deviation) of tumor size and expression of receptors. The basic status of the estrogen receptor (ER), progesterone receptor (PR), cell proliferation marker Ki-67 (ki67), and human epidermal growth factor receptor 2 (HER2) play a crucial role in molecular subtypes classification of breast cancer. Student’s t-test showed significant difference for all the observed variables between cases and controls, excluding size. Fisher’s exact test did not show significant difference for HER2+. CI: confidence interval.