A doctor will rely on final pathology of the tumour to determine the grade and stage of the cancer.  The grade is usually only determined after the tumour has been removed. The grade of cancer relates to how healthy or unhealthy cells look under a microscope. In other words, a pathologist will determine the grade of cancer by comparing the amount of the healthy-looking tissue to the amount of cancerous tissue.  If most of the tumour cells look like normal tissue then the cancer is “well differentiated” or “low-grade.”  However, if the tumour cells look very different from normal tissue then the cancer is “poorly differentiated” or “high-grade.” The grade of cancer may help to determine how quickly the cancer is likely to spread.

Oral cancer grading is described as the following:

Grade Definition
GX The grade cannot be evaluated.
G1 The cells look more like normal tissue and are well differentiated.
G2 The cells are only moderately differentiated.
G3 and G4 The cells don’t look like normal tissue and are poorly differentiated.