“…We found that tumors positive for HER2 had more decline in Ki67 compared with those negative for it but with statistically insignificant difference, these finding also observed in Yulian et al study who investigated the role of statin (simvastatin) in inhibiting proliferation of breast cancer cells, but they found significant difference in both HER2 positive and HER2 negative tumors [18], our expectation was that these molecular factors would significantly affect the treatment response in term of comparable decrease in Ki67 index, but the results were contrary to our expectation. In our study, we found that the most factor that has impact on post-treatment ki67 changes is tumor grade, regarding the tumor grade, there were four cases (13.3%) with grad I, sixteen (53.3%) with grade II and ten (33.3%) with grade III, after treatment with atorvastatin there was remarkable Ki67 changes regarding tumor grade, in grade I cases, 50% of them had unchanged Ki67, 25% increased and 25% decreased , in grade II cases, 6.3% of them had unchanged Ki67, 56.3% decreased and 37% increased compared with those with grade III, in whom Ki67 decreased in 90% of them (p=0.05) with statistically significant difference (Table 3), these results were similar in various studies that were conducted to evaluate the role of statins in breast cancer [1,3,18,19]. Finally, the antiproliferative effect of statins, which was established in this study, was supported by previous in-vitro and in-vivo studies not only in breast cancer, but also in other malignancies [20][21][22] and encouraging further researches to incorporate statins in the neo-adjuvant and adjuvant breast cancer treatment.…”