Grading is a way of classifying cancer cells based on their appearance and behaviour when viewed under a microscope. The doctor needs to know how different the cancer cells look from normal cells, how frequently they are dividing (mitoticmitoticThe process by which a cell divides to form 2 new cells. Each new cell receives a complete set of chromosomes from the original cell. activity) and how likely they are to spread to new locations.
Differentiation refers to how cancer cells look and function compared to normal cells. A tumour's level of differentiation can vary with time and can be described in degrees.
Some tumours are described as low grade or high grade. Their grade is based on their degree of differentiation and their growth rate.
Sometimes tumour grade is described with a number between 1 and 4. The number refers to the degree of differentiation:
grade cannot be assessed
Different grading systems may be used for different types of cancer. Some types of cancer do not have specific grading criteria. For most types of cancer, grading plays an important part in planning treatment and can also be used to help estimate the future outcome (prognosis). Generally, a lower grade represents a more favourable prognosis. However, grading may not be particularly useful for some types of cancer.