Considering the relevance of Eg5 in BC and the hypothetic mechanisms of action used by this protein to induce the onset or progression of tumor, it could be a new possible biomarker in addition to all the panel of markers already known: ER, PR, HER2, p5, Ki-67, BRCA1/BRCA2, PTEN, and others [85]. Here, KIF11 is linked to neoplasm.