What does Ki-67 mean?
Understanding this cell-growth marker
The short version
Ki-67 is a marker that shows what percentage of cancer cells are actively dividing. A higher percentage can suggest faster-growing cells, and may factor into treatment decisions alongside other results.
is a protein found in dividing cells. A pathologist can measure the percentage of cancer cells that test positive for Ki-67 to get a sense of how quickly the tumor may be growing — a higher percentage generally suggests faster growth.
Ki-67 testing and its cutoffs for "high" versus "low" are not fully standardized between labs, so results are usually interpreted alongside grade, stage, and biomarker status rather than alone.
Questions you may want to ask
What was my Ki-67 result, and how does it factor into your recommendation?