MKI67 and invasive ductal breast carcinoma: The fresh breast invasive ductal carcinoma formalin-fixed paraffin-embedded specimens tissue sections (thickness: 4 μm) from 30 patients with different Ki67 index (10 patients with low grade of Ki67 index ≤ 10%, 10 patients with moderate grade of Ki67 index > 10% and < 50%, and 10 patients with high grade of Ki67 index ≥ 50%) independently interpreted by two BC pathologists with rich experience based on IHC Ki67 staining were selected for this study.