Tumor grade is a system which classifies cancer cells by how abnormal they appear under the microscope and how quickly the tumor is likely to grow and spread. Many factors are considered when determining tumor grade including the structure and growth pattern of the cells.
Histologic grade, or differentiation, refers to how much the tumor cells resemble normal cells of the same tissue type. Nuclear grade, refers to the size and shape of the nucleus in tumor cells and the percentage of tumor cells that are dividing.
When cancer is suspected, the doctor removes one or more samples of tissue during a biopsy procedure. The tissue is then sent to the laboratory where a pathologist examines the tissue to confirm whether or not the tumor is malignant. Tumor grade and other tumor characteristics are also determined at this time.
Based on the appearance of the cancer cells under the microscope, the pathologist assigns a tumor grade (1 through 4) based on severity. Grade 1 cells most closely resemble normal cells, and tend to grow and spread more slowly; Grade 3 and 4 cells are grossly abnormal cells, and tend to grow and spread more rapidly.
The American Joint Commission on Cancer recommends the following tumor grading guidelines, however, grading systems may vary according to the type of cancer involved.
|GX||Grade unable to be assessed||Undetermined grade|
|G2||Moderately differentiated||Intermediate grade|
|G3||Poorly differentiated||High grade|
The doctor considers many factors, including stage and tumor grade, when formulating an individual’s treatment plan and predicting prognosis. Patients should speak frankly with their doctor about how these factors relate to their possible treatment options.