Understand your Tumour Grade and Ki-67
Grade is not stage, and grade 3 is not the worst line on your report. Here is what a pathologist actually scores, and why a faster-behaving cancer is not automatically the harder one to treat.
Grade is not Stage
Grade 3 does not mean stage 3. You are usually handed both numbers on the same day, they sound alike, and they answer completely different questions.
- Stage — how far it has spread.
- Grade — how the cells look and behave close up.
Stage is how far the fire has spread through the building. Grade is how hot it is burning. Two different questions, answered separately.
They also do not move together. An early cancer can be grade 3, and a later one can be grade 1. How staging works →
What your grade actually means
This is the whole of it. Three possible answers, and yours is one of them.
Still much like healthy cells
The cells look and behave close to normal breast cells, and are growing slowly.
Somewhere in between
Not close to normal, not far from it. The most common of the three.
Least like healthy cells
The cells look least like normal ones and are growing faster. Why that is not automatically worse news ↓
It does not tell you how far the cancer has spread — that is the stage. It does not tell you what treatment you will have. And it does not tell you what will happen to you.
How they work the grade out
The grade is not one doctor’s opinion. A pathologist — the doctor who examines your tissue under a microscope — checks three things separately. Each gets a score. The three are added up.
1 · Are the cells still doing their job? tubule formation
Healthy breast cells form tiny tubes. That is their job. The more the cancer cells have stopped doing it, the higher this score.
2 · Do the cells look alike? nuclear pleomorphism
A frightening word for a simple question. If the cells look much the same as each other, this scores low. If they are a mixed bag of shapes and sizes, it scores high.
3 · How many were dividing? mitotic count
Cells grow by splitting in two. This counts how many were caught doing it.
A photograph of a busy road tells you how many cars were moving at that instant. It does not tell you the total traffic for the day. The mitotic count is that photograph.
It is a count at one moment — not a growth rate, and not a prediction.
See how the score adds up
If your report lists the three scores, set them here. It is a sum, not an opinion — which is why two different labs looking at the same tissue should land on the same grade. The sum is fixed. What the grade means for you is not.
Many reports show only the final grade and not the three parts. That is normal.
Grade 1
The cells still look and behave much like normal breast tissue.
What this does not tell you: what will happen to you. Grade is one piece, read together with the stage, the ER/PR/HER2 line and your general health.
This only shows how the sum works. It is not a diagnosis, it says nothing about what will happen to you, and it is no substitute for your oncologist reading your case.
How the total maps to a grade
- Lowest totals
- Grade 1 — the cells still look and behave much like healthy breast cells.
- Middle totals
- Grade 2 — in between, on all three features or on some of them.
- Highest totals
- Grade 3 — the cells look least like healthy ones, and more were caught dividing.
- Still forming tubes?
- Scores low when most cells still form tubes, high when few do.
- Cells look alike?
- Scores low when the cells look much the same, high when they vary a lot.
- Caught dividing?
- Scores low when few cells were caught dividing, high when many were.
What is Ki-67?
Cells grow by splitting in two. Ki-67 is a marker that only shows up in cells getting ready to split.
- The lab stains your tissue. Cells preparing to divide light up.
- Ki-67 is simply the count of how many lit up.
- A higher number means more were getting ready to divide when the sample was taken.
It gives your team a second read on how fast the cancer is behaving, alongside the grade.
It is a photograph, not a speedometer. It counts what was happening in one moment. It does not tell you how fast things will go from here.
Labs do not agree on where low ends and high begins. A number that looks frightening against something you read online may be perfectly ordinary against the scale your lab uses. Ask what your number meant to the doctor who read it.
A higher grade is not automatically worse news
A higher grade does mean the cells are growing faster. But that cuts both ways, and almost nobody is told this part.
- Treatments that act on dividing cells have more to act on when more cells are dividing.
- Grade is one piece of several — weighed with the stage, the ER/PR/HER2 line and your general health.
A faster-growing cancer is not automatically the harder one to treat. It often gives treatment more to work with.
That is not a promise about outcome. It is a reason not to read this one line as a sentence.
Worried about a grade 3 result? Send us the report. An oncologist will tell you what it means alongside everything else on the page.
Get my grade explainedWant your report read properly?
Bring the lab report and the slides if you have them. An oncologist will explain what your grade and Ki-67 mean alongside the stage and the ER/PR/HER2 line. That is the only way either number means anything.
Or call 1800 202 8726 — toll free, no obligation.
Support that comes with your treatment
At CION these run alongside treatment, not as afterthoughts.
Nutrition
Appetite, weight and strength through treatment.
Psychology
Support for patient and family.
Genetic counselling
Hereditary risk for you and close relatives.
Rehabilitation
Shoulder mobility and lymphoedema care.
Screening
Regular checks for you and close relatives.
Second opinion
A written review of your report and plan.
Your grade means something only alongside everything else
An oncologist will read the grade, the Ki-67, the stage and the ER/PR/HER2 line together, and tell you what follows from them. Bring the printout, and the slides and wax block if you have them.
Toll free 1800 202 8726 · Advancing Care. Passionately.