Despite the fact that tumor volumes were significantly lower in the Z-endoxifen arm compared to the tamoxifen arm (Additional file 2), both Z-endoxifen (p = 0.0005) and tamoxifen (p = 0.008) significantly suppressed nuclear Ki-67 expression compared to letrozole-treated MCF7LR tumors (Additional file 6a and b). Here, MKI67 is linked to neoplasm.