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How is tumor grade determined?
If a tumor is suspected to be malignant, a doctor removes a sample of tissue or the entire tumor in a procedure called a biopsy. A pathologist (a doctor who identifies diseases by studying cells under a microscope) examines the tissue to determine whether the tumor is benign or malignant. The pathologist can also determine the tumor grade and identify other characteristics of the tumor cells.
What do the different tumor grades signify?
Based on the microscopic appearance of cancer cells, pathologists commonly describe tumor grade by four degrees of severity: Grades 1, 2, 3, and 4. The cells of Grade 1 tumors resemble normal cells, and tend to grow and multiply slowly. Grade 1 tumors are generally considered the least aggressive in behavior.
Conversely, the cells of Grade 3 or Grade 4 tumors do not look like normal cells of the same type. Grade 3 and 4 tumors tend to grow rapidly and spread faster than tumors with a lower grade.
|GX||Grade cannot be assessed (Undetermined grade)|
|G1||Well-differentiated (Low grade)|
|G2||Moderately differentiated (Intermediate grade)|
|G3||Poorly differentiated (High grade)|
|G4||Undifferentiated (High grade)|
Does the same grading scale apply to all tumors?
Grading systems are different for each type of cancer. For example, pathologists use the Gleason system to describe the degree of differentiation of prostate cancer cells. The Gleason system uses scores ranging from Grade 2 to Grade 10. Lower Gleason scores describe well-differentiated, less aggressive tumors. Higher scores describe poorly differentiated, more aggressive tumors. Other grading systems include the Bloom-Richardson system for breast cancer and the Fuhrman system for kidney cancer.