The grade of a cancer describes how much the tumour cells look like healthy cells under a microscope, or how abnormal they look; the more abnormal they are, the faster the tumour usually grows [1]. A pathologist sets the grade on a tissue sample, and it is usually written as grade 1 (well differentiated, low grade) to grade 3 (poorly differentiated, high grade); some cancers also have a grade 4 [1]. Grade is not the same as stage: the stage tells you how big the tumour is and how far in the body it has reached, not what its cells look like [1].
Key points
- A low grade (1) means the cells look more like healthy cells and the tumour usually grows more slowly; a high grade (3 or 4) means the cells look very abnormal and the tumour usually grows faster [1].
- A high grade does not mean the cancer has spread; spread is shown by the stage [1].
- Breast cancer only has grades 1 to 3 [2]; when people talk about "grade 4 breast cancer", they usually mean stage 4.
- Each cancer has its own grading system; for example, prostate cancer uses "Grade Groups" 1 to 5 (the Gleason score) and brain tumours use grades 1 to 4 [6, 11].
- Your doctor considers the grade together with the stage, the type of tumour, genetic tests on the tumour, your age and your general health; grade alone does not decide how the illness will go [1].
How is the grade of a cancer worked out?
After a biopsy or surgery, a doctor who specialises in diagnosing disease from tissue (a pathologist) stains very thin slices of the tissue and looks at them under a microscope [1]. The pathologist checks how much the cells and the tissue structure look like the healthy tissue of the same organ, and how many cells are dividing [1, 3].
How closely tumour cells resemble healthy cells is called "differentiation". A tumour that still looks like healthy tissue is "well differentiated", and one that no longer looks like healthy tissue at all is "undifferentiated" [1]. In some cancers, such as breast cancer, the pathologist scores several features of the cells separately and adds up the scores to get the grade [2, 5]. Read more about biopsies: What is a biopsy?
What do well, moderately and poorly differentiated mean?
| What the pathology report says | Grade | What it means in plain words |
|---|---|---|
| Well differentiated | Grade 1, low grade | The cells look like healthy cells; the tumour usually grows slowly [1] |
| Moderately differentiated | Grade 2, intermediate grade | The cells look somewhat abnormal; in between grade 1 and grade 3 [1] |
| Poorly differentiated | Grade 3, high grade | The cells look very abnormal; the tumour usually grows faster [1] |
| Undifferentiated | Grade 4, high grade | The cells look nothing like healthy tissue [1] |
| GX | Unknown | The grade cannot be assessed [1] |
Some reports give the words, some give the grade number, and many give both.
For example, "moderately differentiated adenocarcinoma" means a cancer of gland-forming cells that is grade 2. In bowel (colorectal) cancer this is the most common finding: about 7 in every 10 tumours are moderately differentiated [9].
"Poorly differentiated" means grade 3, or high grade: the cells look little like healthy cells, and the tumour may grow faster and need treatment sooner [1].
What is the difference between grade and stage?
| Grade | Stage | |
|---|---|---|
| What does it show? | How abnormal the tumour cells look under the microscope and how fast the tumour is likely to grow [1] | How big the tumour is and whether it has reached the lymph nodes or distant parts of the body [1] |
| How is it written? | Grade 1 to 3 (up to 4 in some cancers), or well, moderately and poorly differentiated [1] | Stage 0 to 4, or the letters T (tumour), N (lymph nodes) and M (spread to a distant site) [4] |
| Example | A grade 3 breast cancer may be small and may not have reached any lymph node [3] | Stage 4 breast cancer means the cancer has reached another organ of the body, whatever its grade [4] |
Grade and stage are two different things, but both matter. In a large review of more than 20,000 people with breast cancer, people with a grade 1 cancer at stage 2 lived as long as people with a grade 3 cancer at stage 1 [3]. This is why the current breast cancer staging system uses the grade, together with the hormone receptors and HER2, to set the stage [4]. Read more about stages: What are the stages of cancer?
In breast cancer, the grade only goes from 1 to 3 [2, 5]. When people talk about "grade 4" breast cancer, they usually mean "stage 4": a cancer that has reached a distant part of the body such as the bones, lungs or liver [4]. If you are not sure, ask your doctor: "What is the grade of my tumour, and what is its stage?"
How much does grade affect treatment and life expectancy?
High-grade tumours may grow quickly and may need treatment sooner or more intensive treatment [1]. But doctors never decide on grade alone; the stage, the type of tumour, the genetic features of the tumour, your age and your general health also matter [1].
One important step: go through your pathology report with your doctor and ask how the grade of your tumour affects your treatment. The guide How to read your pathology report helps you know what to ask.
Grade in different cancers
Each cancer has its own grading system, and the number of grades is not the same in all of them [1]. This table shows some important examples:
| Cancer | Grading system | Grades | Note |
|---|---|---|---|
| Breast cancer | Nottingham grade: three features of the cells are scored separately [2] | Grade 1 to 3 [2] | There is no grade 4; in one large study, about 4 in every 10 tumours were grade 3 [3] |
| Prostate cancer | Gleason score and Grade Group [6] | Grade Group 1 (Gleason 6) to 5 (Gleason 9 and 10) [6, 7] | Gleason 6 is the lowest grade, even though the number seems to sit in the middle [6] |
| Bowel (colorectal) cancer | How much the cells still form glands [9] | Low grade (well or moderately differentiated) and high grade (poorly differentiated) [9] | If the report says "grade 4" or "undifferentiated", that also counts as high grade [1] |
| Brain and spinal cord tumours | World Health Organization grading, together with genetic tests on the tumour [11] | Grade 1 to 4 [11] | Glioblastoma is grade 4 [11] |
Grade 1, 2 and 3 breast cancer: treatment and life expectancy
The grade of a breast cancer comes from adding up the scores for three features: how much the cells still form ducts (tubes), how abnormal the cell nuclei look, and how many dividing cells can be seen [2]. Grade 3 cancers usually grow faster and are more likely to come back in the first years [3].
Treatment of grade 3 breast cancer: grade 3 does not mean that the cancer has spread or cannot be treated [1]. The stage and the tumour's receptors (hormone receptors and HER2) also play a big part in choosing the treatment [1, 4]. With grade 3, your doctor is more likely to suggest chemotherapy after surgery as well, because these tumours come back sooner [3]. Grade 1 tumours are almost always hormone receptor positive, and lighter treatment such as hormone therapy is often considered [3].
Life expectancy with grade 2 breast cancer: grade is only one factor, and the stage and the receptor type also matter [3, 4]. A large study looked at women whose breast cancer was hormone receptor positive and had not reached the lymph nodes, and who had only hormone therapy after surgery. Of every 7 women with grade 2 cancer, 6 had no return of the cancer over the next 10 years. The chance of the cancer coming back was about twice as high with grade 3 as with grade 2, and about twice as high with grade 2 as with grade 1 [3]. Knowing all the features of your tumour, your doctor can give you a clearer picture. Read more: Breast cancer
Bowel cancer grading: low grade, high grade and "grade 4"
In bowel (colorectal) cancer, the grade is based on how much the cancer cells still form gland structures [9]. The grade may be given as three levels (well, moderately or poorly differentiated) or as two: low grade (well or moderately differentiated) and high grade (poorly differentiated). Studies have shown that the two-level system is more reliable and predicts the outcome better [9]. If your report says "grade 4" or "undifferentiated", this also counts as high grade [1].
A high grade is linked to a worse outcome [9]. In stage 2 bowel cancer, poor differentiation is one of the signs that make the cancer more likely to come back, and doctors weigh it when deciding about chemotherapy after surgery [10]. Even so, the outcome clearly depends on how far the tumour has grown through the bowel wall, whether it has reached the lymph nodes and whether it has spread to a distant site [10]. Read more: Colorectal cancer
Prostate cancer grade (the Gleason score)
In prostate cancer, the pathologist scores the two main patterns of the cells, and their sum is the "Gleason score", for example 3+3=6 or 4+3=7 [6]. Because 6 is the lowest score given today and can frighten patients for no reason, the scores have been simplified into five "Grade Groups": Grade Group 1 (Gleason 6) is the lowest risk and Grade Group 5 (Gleason 9 and 10) the highest [6, 7]. Many men with low-risk cancer can be followed with regular check-ups instead of having treatment straight away [8]. Read more: Prostate cancer
Brain tumour grade (grades 1 to 4)
Tumours of the brain and spinal cord are graded from 1 to 4 [11]. Grade 1 tumours grow slowly; grade 2 tumours are also slow, but they may grow into nearby tissue and come back; grade 3 tumours grow faster, and grade 4 tumours grow and spread very quickly [12]. Today, besides what the cells look like, genetic tests on the tumour also help set the grade [11]. For example, glioblastoma is always grade 4 [11]. Read more: Brain tumours
Frequently asked questions
Does a high grade mean the cancer has spread?
Does grade 1 mean my cancer is not dangerous and does not need treatment?
What does poorly differentiated mean? Is it very bad?
Poorly differentiated means the tumour cells look little like healthy cells; it is the same as grade 3, or high grade [1]. These tumours usually grow faster and may need treatment sooner or more intensive treatment [1]. But poorly differentiated does not mean the cancer cannot be treated; the result of treatment also depends on the stage and other factors [1].
The grade on my biopsy is different from the grade after surgery; which one is right?
A needle biopsy removes only a small piece of the tumour, whereas after surgery the whole tumour is examined [3]. In breast cancer, grade 1 on a needle biopsy changes to grade 2 after surgery in about a third of cases; but a change from grade 1 to grade 3, or the other way round, is very rare [3]. If the two results differ, ask your doctor which one they will base the treatment decision on.
Does Gleason 6 mean my prostate cancer is intermediate?
No. The Gleason score originally runs from 2 to 10, but today the lowest score given to a cancer is 6; so Gleason 6 (Grade Group 1) is the lowest grade of prostate cancer [6].
What does grade 3 breast cancer mean, and can it be treated?
Grade 3 means the tumour cells look very abnormal under the microscope and the tumour usually grows faster [1]. But grade 3 does not mean the cancer cannot be treated [1]. The stage and the tumour's receptors also play a big part in choosing the treatment [1, 4]. With grade 3, doctors often consider chemotherapy as well, because these tumours come back sooner [3].
Related pages
Grading systems and criteria (for doctors)
For physicians
Breast (Nottingham grade, the Elston–Ellis modification of the Bloom–Richardson method). Three semi-quantitative components: percentage of tubule formation, nuclear pleomorphism and an accurate mitotic count in a defined field area; the overall grade comes from the sum of the scores [2]: a total of 3 to 5 = G1, 6 to 7 = G2 and 8 to 9 = G3 [5]. In 1831 patients of the Nottingham series, survival with G1 was significantly better than with G2 and G3 (P<0.0001) [2]. In the 1990–2002 series (3579 patients), 18.9% were G1, 38.6% G2 and 42.4% G3. In ER-positive/HER2-negative disease (1077 patients) grade was an independent predictor of RFS (HR 2.13; 95% CI 1.79 to 2.53); the 10-year risk of relapse was 7%, 14% and 31% in the LN-negative subgroup treated with endocrine therapy alone (797 patients) and 5%, 24% and 43% in pN1 (316 patients) for G1 to G3. In Henson et al. (22,616 patients), survival with G1 stage II equalled that with G3 stage I. On needle core biopsy, upgrading from G1 to G2 on the excision specimen is reported in 30 to 40%, a change of G3 in 5 to 8% and a shift between G1 and G3 in 0 to 1% [3]. The AJCC 8th edition added grade, together with ER, PR and HER2 (and, where available, a low Oncotype DX score), to the prognostic stage [4].
Prostate (ISUP 2014, WHO 2016). Grade Group 1: Gleason ≤6; 2: 3+4=7; 3: 4+3=7; 4: 8; 5: 9 to 10. Pattern 4 includes cribriform, fused and poorly formed glands; unequivocal comedonecrosis, even if focal, is pattern 5; intraductal carcinoma without invasive carcinoma is not assigned a Gleason grade [6]. In the multi-institutional validation (20,845 radical prostatectomies and 5501 radiotherapy patients), the HRs for biochemical recurrence in the surgery cohort relative to Gleason 6 were 1.9, 5.1, 8.0 and 11.7 for 3+4, 4+3, 8 and 9 to 10, respectively [7]. EAU 2026: active surveillance is the appropriate management for low-risk disease and for selected favourable intermediate-risk ISUP grade group 2 lesions [8].
Colorectum. Well differentiated: more than 95% gland formation; moderately: 50 to 95%; poorly: mostly solid with less than 50% gland formation. About 70% of tumours are moderately, 10% well and 20% poorly differentiated. A two-tier system (low grade with 50% or more gland formation, high grade less than 50%) reduces interobserver variation and improves prognostic value; grading applies to conventional adenocarcinoma, and some subtypes with high-grade morphology behave as low grade because of MSI [9]. In stage II, poorly differentiated histology, together with inadequate lymph node sampling, T4 disease and involvement of the visceral peritoneum, is among the features associated with an increased risk of recurrence [10].
Central nervous system (WHO 2021, fifth edition). Grades are written in Arabic numerals (1 to 4) and assigned "within tumour types", and molecular markers now contribute to grade and prognosis. Glioblastoma, IDH-wildtype is diagnosed in an adult IDH-wildtype diffuse astrocytic glioma with microvascular proliferation or necrosis, or a TERT promoter mutation, or EGFR gene amplification, or +7/−10 chromosome copy-number changes; astrocytoma, IDH-mutant is graded 2, 3 or 4, and CDKN2A/B homozygous deletion makes it grade 4 [11].
Related cancer types
Related questions
References
12 referencesShow all references, 3 with a study cardClose the reference list
Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
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- 8EAU-EANM-ESTRO-ESUR-ISUP-SIOG Guidelines on Prostate Cancer-2026 Update. Part I: Screening, Diagnosis, and Local Treatment with Curative Intent
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- 12Adult Central Nervous System Tumors Treatment (PDQ®)–Patient Version
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