Generally, tumors are assigned grades to express the degree of malignancy, or the rate at which the tumor is dividing and growing.  A grade can be determined by a biopsy, or analysis of a taken tissue sample.  This system of grading helps provide guidance for predicting a patient’s prognosis, choosing the most appropriate course of treatment, and assigning an accurate stage. There are Grades I through IV, the first being the least aggressive and likely to metastasize to other parts of the body, and Grade IV being the most aggressive with a higher probability of spreading. More on tumor grades.

Tumors are also assigned stages.  This is an estimation for the extent of dissemination (or spread) of the tumor throughout the body, which is important when considering treatment options or qualification for participation in clinical trials. Categorizing systems for assigning staging include UICC and TNM. More on staging.