Tumor Grade: What Low, Intermediate, and High Grade Mean in Your Pathology Report

Section Editor: Jason Wasserman MD PhD FRCPC
November 9, 2026

Tumor grade describes how different the tumor cells look from normal cells when a pathologist examines them under the microscope. A grade appears in the pathology report for most cancers and many precancerous changes. In general, a low grade means the cells still look and behave much like normal cells. A high grade means they look very abnormal and tend to grow faster. This article explains how tumor grade is decided and why a grade of 2 means different things in different cancers. It also explains what the grade in your pathology report means for your care.

What is the difference between tumor grade and stage?

Tumor grade and stage are both found in a cancer pathology report, but they describe different things. The grade describes what the cancer cells look like under the microscope. The stage describes how large the tumor is and how far it has spread in the body. Patients often confuse the two because both are written as numbers.

A grade 3 cancer is not the same as a stage 3 cancer. A small cancer found early can be high grade, and a large cancer that has spread can be low grade. The pathologist assigns the grade from the tissue alone. The stage combines the pathology findings with imaging and examination, and the TNM staging system is the most common way it is reported. In some cancers, grade is also one of the factors used to determine overall stage. Breast cancer, prostate cancer, and soft tissue sarcoma are examples.

How do pathologists decide the tumor grade?

Pathologists determine tumor grade by comparing tumor cells with normal cells from the organ where the tumor started. Each grading system looks at a slightly different set of features, but most use some combination of the features below.

Resemblance to normal tissue. This is called differentiation. A tumor that still forms structures like the normal organ, such as glands, is well differentiated. A tumor that has lost those structures is poorly differentiated.
Appearance of the nucleus. The nucleus is the part of the cell that holds its genetic material. Large, dark, or irregular nuclei that vary in shape from cell to cell point toward a higher grade. Some systems score this as a nuclear grade.
How quickly the cells are dividing. Pathologists count dividing cells, called mitotic figures, to give a mitotic rate. Some tumors are also tested with Ki-67, a stain that marks dividing cells.
Areas of dead tumor. Some systems include tumor necrosis, which is tumor tissue that has died, usually because it grew faster than its blood supply.
The pattern of growth. In prostate cancer, the grade is based mainly on the patterns the cancer cells make as they grow, rather than on individual cells.

Some grading systems combine these features into a score, while others rely on overall judgment. In some brain tumors, molecular testing can also determine the grade based on genetic changes.

How is tumor grade written in a pathology report?

Tumor grade can be written in several ways in a pathology report, depending on the cancer type and the laboratory. Two reports describing tumors of similar grade can therefore look quite different. The most common formats are listed below.

Well, moderately, or poorly differentiated. These words describe how closely the tumor resembles normal tissue. Moderately differentiated sits in the middle. A tumor with no resemblance to normal tissue may be called undifferentiated.
G1, G2, G3, and G4. Many cancer reports use these letters and numbers. G1 is well differentiated, and G2 is moderately differentiated. G3 is poorly differentiated, and G4, when it is used, is undifferentiated. GX means the grade could not be assessed.
Grade 1, 2, or 3. Some systems use only numbers, such as the Nottingham grade in breast cancer. Grade 1 is the lowest and grade 3 is the highest.
Low grade and high grade. Several cancers and most precancerous changes are graded in only two levels. This two-level approach is often more consistent between pathologists than a three-level one.
A score made from parts. Some grades are built from smaller scores, such as a Gleason score of 3 + 4 = 7 in prostate cancer. The report may show both the parts and the total.

Because the scales differ, a number alone does not tell you whether the grade is low or high. A grade 2 is the middle of a three-level scale, but the second-lowest step on a four-level scale. Your report or your doctor can tell you how many levels the system used for your cancer has.

Why does tumor grade mean different things in different cancers?

Tumor grade means different things in different cancers because each type of cancer has its own grading system. Each system was built around the features that best predict how that particular cancer behaves. The sections below describe the grading systems you are most likely to see, with links to articles that explain each cancer in more detail.

Breast cancer: Nottingham grade

Invasive breast cancer is graded with the Nottingham histologic grade. The pathologist gives a score of 1 to 3 for each of three features: gland formation, nuclear appearance, and mitotic rate. The pathologist adds the three scores for a total of 3 to 9. A total of 3 to 5 is grade 1, 6 or 7 is grade 2, and 8 or 9 is grade 3. Reports for invasive ductal carcinoma and other invasive breast cancers often list all three scores as well as the final grade.

Prostate cancer: Gleason score and Grade Group

Prostate cancer is graded by the patterns its cells form, using the Gleason score. The two most common patterns are each given a number, and the two numbers are added together. In practice, scores run from 6 to 10. The International Society of Urological Pathology (ISUP) introduced Grade Groups in 2014 to make the score easier to understand.

Grade Group 1. Gleason score 6 (3 + 3). This is the lowest grade of prostate cancer seen in practice.
Grade Group 2. Gleason score 7, made up of 3 + 4. Most of the cancer is the lower pattern.
Grade Group 3. Gleason score 7, made up of 4 + 3. Most of the cancer is the higher pattern, so it behaves differently from Grade Group 2.
Grade Group 4. Gleason score 8.
Grade Group 5. Gleason score 9 or 10. This is the highest grade.

The prostate adenocarcinoma article explains Gleason patterns in more detail.

Kidney cancer: WHO/ISUP grade

The two most common types of kidney cancer, clear cell renal cell carcinoma and papillary renal cell carcinoma, are graded with the WHO/ISUP system. It uses four grades, from 1 to 4, based mainly on how prominent a small structure inside the nucleus, called the nucleolus, looks. Grade 4 also includes tumors with very bizarre cells or sarcoma-like areas. Chromophobe renal cell carcinoma is not graded with this system, because it has not been shown to predict how that type behaves. Older reports may use the Fuhrman grade, which the WHO/ISUP grade has replaced.

Colon and rectal cancer: low grade and high grade

Under the 2019 WHO classification, adenocarcinoma of the colon and rectum is graded as low grade or high grade. The grade is based on how well the cancer forms glands. Low grade replaces the older terms well and moderately differentiated, and high grade replaces poorly differentiated. The grade is based on the least differentiated area of the tumor so that a small high-grade area can make the whole tumor high grade.

Endometrial cancer: FIGO grade

Endometrioid carcinoma of the endometrium is given a FIGO grade of 1, 2, or 3. The grade is based mainly on how much of the tumor grows in solid sheets instead of glands. In the FIGO 2023 staging system, grades 1 and 2 are grouped as low grade, and grade 3 is high. Several other types, including serous carcinoma, clear cell carcinoma, and carcinosarcoma, are treated as high grade by definition and are not given a FIGO grade. In FIGO 2023, whether the cancer is low- or high-grade can change the stage itself.

Bladder cancer: low grade and high grade

Papillary urothelial carcinoma of the bladder is graded as low grade or high grade. Under the 2022 WHO classification, a tumor is reported as high grade when high-grade cells make up 5% or more. Low-grade tumors often come back after removal but rarely spread, while high-grade tumors are more likely to grow into the bladder wall. Most cancers that have already grown into the bladder wall are high grade.

Neuroendocrine tumors: grade by Ki-67 and mitotic count

Well-differentiated neuroendocrine tumors of the digestive system are graded by how fast the cells are dividing. The 2019 WHO classification uses three grades.

Grade 1. A Ki-67 index below 3%.
Grade 2. A Ki-67 index of 3% to 20%.
Grade 3. A Ki-67 index above 20%.

The mitotic count is used in the same way, and the higher of the two results sets the grade. Neuroendocrine carcinomas are a different group of cancers that are poorly differentiated and high grade by definition.

Soft tissue sarcoma: FNCLCC grade

Most soft tissue sarcomas are graded with the FNCLCC system. It adds scores for differentiation, mitotic count, and tumor necrosis to give a final grade of 1, 2, or 3. Some types of sarcoma, such as synovial sarcoma and angiosarcoma, are high grade by definition. Others are not graded with this system.

Brain and spinal cord tumors: WHO CNS grade

Tumors of the brain and spinal cord use the WHO CNS grading system, with grades 1 to 4, most recently revised in 2021. Unlike most other systems, the grade is usually set by tumor type rather than by each case. For example, every glioblastoma is grade 4. Molecular testing can identify genetic changes that raise the grade, even when the cells look less abnormal. In the brain, a low grade does not mean harmless, because a slow-growing tumor can still cause serious problems because of where it is.

Squamous cell carcinoma and other cancers: degree of differentiation

Squamous cell carcinoma can start in many parts of the body, including the skin, mouth, and lung. It is usually graded as well, moderately, or poorly differentiated. The grade is based mainly on how much the cancer cells make keratin, the tough protein made by normal squamous cells. Many other cancers, including adenocarcinomas of the stomach, pancreas, and lung, also use the well-, moderately, and poorly-differentiated scale. For most of these cancers, grade has less effect on treatment than stage.

What does it mean if my report gives more than one grade?

A pathology report can give more than one tumor grade for several reasons, and this is common. Cancers are often a mixture of areas that look different from one another. The most common situations are listed below.

A range of grades. A report may say a tumor is “moderately to poorly differentiated.” This means some parts of the tumor look moderately differentiated, while others look poorly differentiated. Most systems treat the tumor according to its higher-grade areas.
Two patterns added together. In prostate cancer, the Gleason score combines the two most common patterns, such as 3 + 4. Both numbers matter, because the order changes the Grade Group.
Component scores and a final grade. In breast cancer, the report may list scores for gland formation, nuclear grade, and mitoses, followed by the final Nottingham grade. The final grade is the one used for staging and treatment decisions.
Separate grades for precancer and cancer. A breast report may give a nuclear grade for ductal carcinoma in situ (DCIS) and a separate Nottingham grade for the invasive cancer. These describe two different parts of the tissue.
More than one tumor. When there is more than one tumor, each one may be graded separately. The report usually makes clear which grade belongs to which tumor.

Why can the grade on my biopsy differ from the grade after surgery?

The tumor grade on a biopsy can differ from the grade after surgery because a biopsy samples only a small part of the tumor. If the highest-grade area wasn’t in the biopsy, the surgical grade may be higher. This is called upgrading, and it is especially common in prostate cancer.

For this reason, some biopsy reports describe the grade as an estimate, or note that it is based on limited tissue. When a surgeon removes the whole tumor in a resection, the pathologist can examine much more of it. The surgical grade is usually the one used for final decisions. Less often, the post-surgery grade is lower because the biopsy happened to sample the worst area.

Treatment given before surgery, such as chemotherapy or radiation, can also change how tumor cells look. Some reports do not give a grade after treatment, or note that treatment changes may affect it.

Why does my pathology report not include a tumor grade?

Some pathology reports do not include a tumor grade, and this is expected for many diagnoses. A missing grade does not mean the pathologist forgot to assess it. The most common reasons are listed below.

The tumor is high grade by definition. Some cancers, such as small cell carcinoma, serous carcinoma of the endometrium, and several sarcomas, always behave as high-grade cancers. Giving them a grade would add nothing.
No grading system applies. Some cancers, such as melanoma, chromophobe renal cell carcinoma, and HPV-associated cancer of the oropharynx, are not graded. For these, other findings in the report give more useful information.
The tumor is noncancerous. Most noncancerous (benign) tumors are not graded, because they do not spread.
There was too little tissue. A very small biopsy, or tissue damaged during removal, may not show enough to grade. The report may say the grade cannot be assessed, or give GX.
The grade is reported elsewhere. For some brain tumors, the grade is part of the diagnosis line, such as “glioblastoma, IDH-wildtype, CNS WHO grade 4,” rather than a separate heading.

How is grade used for precancerous changes?

Grade describes precancerous changes, which are abnormal cells that have not yet become invasive cancer. For precancerous changes, the grade describes how abnormal the cells look and how much of the lining they fill. It helps predict the risk that the change will become cancer if it is left untreated.

Low-grade and high-grade dysplasia. Dysplasia is graded in two levels in the colon, esophagus, and many other organs. High-grade dysplasia carries a much higher risk of becoming cancer than low-grade dysplasia.
Squamous intraepithelial lesions. In the cervix and nearby organs, precancerous changes of squamous cells are graded as low grade (LSIL) or high grade (HSIL). In the cervix, they may also be graded as CIN 1, 2, or 3.
Nuclear grade in DCIS. Ductal carcinoma in situ of the breast is given a nuclear grade of low, intermediate, or high. High-grade DCIS is more likely to come back or to be found with invasive cancer.

What does tumor grade mean for my outlook and treatment?

Tumor grade helps predict how a cancer is likely to behave, and your care team uses it to plan treatment. In general, low-grade cancers grow more slowly and are less likely to spread, while high-grade cancers grow faster and are more likely to spread. Grade is rarely used alone. Your team combines it with the stage, cancer type, and the results of other tests.

How much the grade matters depends on the type of cancer. In some cancers, it is one of the most important findings, while in others, the stage matters far more. Some examples of how grade guides decisions are listed below.

Prostate cancer. For low-risk prostate cancer, which includes most Grade Group 1 cancers, the 2022 American Urological Association and ASTRO guideline describes active surveillance as the preferred option. Higher Grade Groups are more likely to lead to discussion of surgery or radiation.
Breast cancer. The Nottingham grade is used with hormone receptor and HER2 results, and sometimes genomic tests, when the team considers whether chemotherapy may help.
Endometrial cancer. Under FIGO 2023, a high-grade or aggressive type of endometrial cancer can be assigned a higher stage, which can change the treatment that is considered.
Soft tissue sarcoma. The FNCLCC grade is part of the stage, and high-grade sarcomas are more likely to lead to discussion of radiation or chemotherapy.

A low grade does not always mean a cancer is harmless, and a high grade does not mean treatment will not work. Many high-grade cancers respond well to treatment. Your care team can explain what the grade means alongside everything else in your pathology report.

Questions to ask your doctor

What is the grade of my tumor, and which grading system was used?
How many grades does that system have, and where does mine fall?
Is my tumor considered low grade or high grade?
How does the grade affect my stage?
My report lists more than one grade. Which one matters most?
Was the grade based on a biopsy or on the whole tumor?
Could the grade change after surgery?
Why does my report not give a grade?
How does the grade affect the treatment options we are considering?
How does the grade affect my outlook compared with the stage?
If I have a precancerous change, what is the risk that it will become cancer?
Would a second pathologist’s opinion on the grade be helpful?