Ki-67 index
Pronunciation: KAY-eye-sixty-seven
A measure of cellular proliferation expressed as the percentage of Ki-67 positive tumor cells, used in cancer prognosis and treatment decisions.
Full Definition
The Ki-67 index is a biomarker that measures the proliferative activity of tumor cells by quantifying the percentage of cells expressing the Ki-67 protein during active phases of the cell cycle. It is particularly important in breast cancer classification, where it helps distinguish luminal A from luminal B subtypes. Higher Ki-67 values generally indicate more aggressive tumors and may influence decisions regarding chemotherapy. The index is determined by immunohistochemical staining and reported as a percentage.
Usage
Usage note: Always include hyphen; express as percentage when reporting values.
In Context
- "The Ki-67 index was 25%, consistent with intermediate proliferative activity." — pathology report
- "A high Ki-67 index supported the decision for adjuvant chemotherapy." — treatment planning note