Ki-67, named after the location where it was discovered (Kiel University, Germany), is a nuclear nonhistone protein that is universally expressed among proliferating cells and absent in quiescent cells . Ki-67 detects proliferating cells in G1, S, G2, and mitosis, but not in the G0 resting phase. Research studies have shown that high levels of Ki-67 are associated with poorer breast cancer survival . Research studies have explored the use of Ki-67, along with other markers, as potential prognostic or predictive markers in breast cancer and other malignant diseases .
