MKI67 and breast cancer: Despite the large number of published papers analyzing the prognostic role of Ki-67 in early BC, it is still not considered as an established factor to be used in clinical practice, probably because most of the studies are retrospective and because some uncertainty remains on the way Ki-67 should be assessed (Eifel et al, 2001; Goldhirsch et al, 2003; Colozza et al, 2005; Urruticoechea et al, 2005).