Tumor grade is a way of classifying tumors based on certain features of their cells. The grade of a tumor is directly linked to prognosis.
Using a microscope, a pathologist studies the tumor tissue removed during a biopsy to check:
- How much the cancer cells look like normal cells
- How many of the cancer cells are in the process of dividing
The more the cancer cells look like normal cells, the lower the tumor grade tends to be. And, the fewer cancer cells that are dividing, the more likely it is the tumor is growing slowly and the lower the tumor grade tends to be. Together, these factors determine the tumor grade.
For any given tumor size and breast cancer stage, prognosis is poorer with a higher tumor grade (see Figure 4.5). A tumor whose cells look like normal tissue and are slow-growing will most often be classified as Grade 1 (well-differentiated). A tumor whose cells look abnormal and are fast-growing will most often be classified as Grade 3 (poorly-differentiated). Cells that fall somewhere in between are classified as Grade 2 (moderately-differentiated).
Figure 4.5: Tumor Grade and Rate of Metastasis within 10 Years
Women treated with lumpectomy plus radiation between 1970 and 1986 for stage I and II breast cancer*
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Grade
|
Metastasis
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Grade 1 (Well-differentiated)
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15%
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Grade 2 (Moderately-differentiated)
|
26%
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Grade 3 (Poorly-differentiated)
|
29%
|
*This study combined stage I and stage II breast cancers and presented rates of metastasis by grade. However, many other factors have a large impact on your chances of survival. For any given tumor grade, chances of survival will vary greatly depending on these factors.
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Nixon et al., 1996 [16]
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Updated 10/20/11
