The short answer
The Nottingham system grades breast cancer on three microscope features - tubule formation, nuclear pleomorphism and mitotic count - each scored, then added. NCI maps a total of 3-5 points to G1, 6-7 to G2, and 8-9 to G3. Grade describes how the cells look. It is not the stage, and not a prediction about one person.
NCI states the grade of a breast tumor is determined by tubule formation, nuclear pleomorphism, and mitotic count.
NCI maps an SBR score of 3-5 points to G1 (low grade), 6-7 points to G2 (intermediate), and 8-9 points to G3 (high grade).
Grade is not stage. NCI lists grade as one input that combines with TNM, HER2 status and hormone receptor status in prognostic stage grouping.
Grade describes how the cells look under a microscope. It is not by itself a prediction about any one person.
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What is being scored
Your report may call it the Nottingham grade, the SBR or Scarff-Bloom-Richardson score, the histologic grade, or the combined histologic grade. These are names for the same thing.
NCI states that the grade of the tumor is determined by its morphologic features: tubule formation, nuclear pleomorphism, and mitotic count.
In plain terms, a pathologist is looking at three separate questions:
- Tubule formation — how much of the tumor is still arranged into the tube-like gland structures normal breast tissue forms.
- Nuclear pleomorphism — how much the nuclei (the control centers of the cells) vary in size and shape compared with normal cells.
- Mitotic count — how many cells are caught dividing in a measured area of tissue.
Each is scored, and the scores are added. That is why a report often shows something like three separate numbers and a total.
What the total maps to
NCI's grading table sets out the combined grade this way:
- G1 — low combined histological grade (favorable), SBR score of 3-5 points
- G2 — intermediate combined histological grade (moderately favorable), SBR score of 6-7 points
- G3 — high combined histological grade (unfavorable), SBR score of 8-9 points
The lowest possible total is 3, because each of the three features scores at least 1. The highest is 9.
If your report shows only a grade and not the three component scores, asking for them is reasonable.
Grade is not stage
This is the single most common mix-up, and it matters.
Grade describes how the cells look under a microscope. Stage describes how much cancer there is and where it is. They answer different questions and they are arrived at in different ways.
NCI incorporates grade into the clinical and pathological prognostic stage group tables, where it combines with TNM classification, HER2 status and hormone receptor status. So grade is one input among several — not a standalone verdict, and not a substitute for the stage.
NCI lists the grade of the primary tumor among the features that may influence prognosis and the selection of therapy. Among, not alone.
What a grade does not tell you
You may have arrived here having typed your own grade into a search box, wanting to know what it means for you. This page cannot tell you that.
A grade is a description of tissue. It does not say whether the cancer has spread, what your treatment will be, or what will happen. Those answers come from the whole picture — grade alongside stage, receptor status, HER2 status, your own health and your own preferences — held by people who can see all of it.
What this page can tell you is what the number describes, what it is combined with, and which questions get you a real answer.
Questions worth writing down
- What are my three component scores, and what do they add up to?
- Does my report state G1, G2 or G3?
- What is my hormone receptor status and HER2 status, and how do they sit alongside the grade?
- What is my stage, and how was it worked out?
- Does the grade change any of the options being discussed?
- Has a second pathologist reviewed the slides, and can I get a second opinion before deciding?
Related pages
See Grade vs Stage, What Does High Grade Mean?, and What Does Low Grade Mean?.
Sources
Common questions
What does Nottingham grade mean?
It is a way of grading breast cancer from what the cells look like under a microscope. NCI states the grade is determined by morphologic features such as tubule formation, nuclear pleomorphism, and mitotic count. The three scores are added to give a combined histologic grade.
Is Nottingham grade the same as SBR or Bloom-Richardson?
They refer to the same combined histologic grading. NCI's table labels the totals as SBR scores, and reports may use Nottingham, SBR, Scarff-Bloom-Richardson, or "combined histologic grade" for the same thing.
What is the difference between grade 1, 2 and 3?
NCI lists G1 as low combined histological grade (favorable) with an SBR score of 3-5 points, G2 as intermediate (moderately favorable) at 6-7 points, and G3 as high (unfavorable) at 8-9 points.
Is grade the same as stage?
No. Grade describes how the cells look. Stage describes how much cancer there is and where it is. NCI uses grade alongside TNM classification, HER2 status and hormone receptor status when assigning a prognostic stage group.
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Sources last checked: 2026-10-02 what this meansLast updated: 2026-09-17Next planned review: 2027-09-17
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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