Tumor grade facts
- Tumor grade is a system used to classify cancer cells in terms of how abnormal they look under a microscope and how quickly the tumor is likely to grow and spread.
- A pathologist (a doctor who identifies diseases by studying cells under a microscope) determines whether the tumor is benign or malignant. The pathologist also determines the tumor grade.
- Each type of cancer is graded using a different grading system.
- Doctors consider tumor grade and other factors when developing an individual treatment plan for a patient.
What is a tumor?
In order to understand tumor grade, it is helpful to know how tumors form. The body is made up of many types of cells. Normally, cells grow and divide to produce new cells in a controlled and orderly manner. Sometimes, however, new cells continue to be produced when they are not needed. As a result, a mass of extra tissue called a tumor may develop. A tumor can be benign (not cancerous) or malignant (cancerous). Cells in malignant tumors are abnormal and divide without control or order. These cancerous cells can invade and damage nearby tissue, and spread to other parts of the body (metastasize).
What is tumor grade?
Tumor grade is a system used to classify cancer cells in terms of how abnormal they look under a 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. The specific factors used to determine tumor grade vary with each type of cancer.
Histologic grade, also called 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.
Tumor grade should not be confused with the stage of a cancer. Cancer stage refers to the extent or severity of the cancer, based on factors such as the location of the primary tumor, tumor size, number of tumors, and lymph node involvement (spread of cancer into lymph nodes). (More information about staging is available in the NCI fact sheet Staging: Questions and Answers, which can be found at http://www.cancer.gov/cancertopics/factsheet/Detection/staging on the Internet.)
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