In the same study by Schettini et al, patients with HER2 low-expression were found to have higher T-stage, higher N-stage and higher histological grade compared with HER2-0 breast cancer, but there was no significant difference between the two groups in terms of Ki-67 proliferation index and the percentage of tumor-infiltrating lymphocytes (16). This evidence concerns the gene MKI67 and breast carcinoma.