Although several international organizations, including the Italian Association of Medical Oncology [15], European Group on Tumor Markers [16], European Society for Medical Oncology [17], and National Institute for Health and Care Excellence [18] either recommend or consider Ki-67 for use in the prognostic evaluation of breast cancer patients [14], neither the American Society of Clinical Oncology [19,20,21,22] or the National Comprehensive Cancer Network [23] support the use of Ki-67 in the prognostic or predictive evaluation of breast carcinoma. This evidence concerns the gene MKI67 and breast carcinoma.