In the mouse model, animals with MDA-MB-231 xenografts were observed for 39 days (median Ki-67 of 52.5%) and those with MCF-7 xenografts for 75 days (median Ki-67 of 75.0%); ovografts in general were only harvested 5 days after tumor cell engraftment, which might explain the lower ovograft Ki-67 values (MCF-7: median Ki-67 of 15.0%; MDA-MB-231: 30.0%) compared with those seen in the murine xenografts. The gene discussed is MKI67; the disease is neoplasm.