There is similarity to what was demonstrated in breast cancer, where a low Ki67 index in metastasis was associated with longer survival independently of primary tumour proliferation.43 Beside TFI indicating aggressiveness of a disease course, analysis of Ki67 in a metastasis may be beneficial to indicate slowly progressing disease as has already been suggested in breast cancer.43 However, more data are needed to draw any firm conclusions. The gene discussed is MKI67; the disease is breast cancer.