The value of Ki67 in assessing neoadjuvant response has recently been demonstrated by Dowsett et al., who reported that a 2 week pre-operative treatment with the aromatase inhibitor anastrozole was more effective in reducing intratumoral Ki67 levels than tamoxifen, or a combination of anastrozole and tamoxifen, in postmenopausal receptor-positive breast cancer patients (“IMPACT” trial). This evidence concerns the gene MKI67 and breast cancer.