The proliferative fraction (percentage of Ki67-labelled cells) was also not significantly correlated between primary and secondary cancers (r=0.179, P=0.524), though the mean Ki67 was significantly higher in the brain metastases than the primary lung cancers (35.7% vs 19.3%, respectively, P=0.018) (Table 1). The gene discussed is MKI67; the disease is lung cancer.