MKI67 and breast carcinoma: The expression of the Ki-67 antigen, a nuclear protein expressed during the G1, S, G2 and M phases of the cell cycle but not during the resting phase (G0) [8, 9], has emerged as the preferred marker of tumor proliferation in different tissue types [10–13], offering interesting predictive value in breast cancer [14] and neuroendocrine digestive tumors [15].