Staging is the process of testing that evaluates your pet's cancer with regard to tumor size and spread (if the cancer has metastasized or involves other parts of the body). From the information obtained with these tests, a numeric description is given with higher numbers indicating more advanced disease (i.e. stage V is more advanced than stage I). Knowing the stage of your pet's cancer is critical in selecting the proper treatment as well as in establishing their prognosis. The numeric stage is based on initial testing. Therefore, it will not change during the course of your pet’s therapy. The grade of a cancer is different than its stage. Grading requires a tumor biopsy and microscopic description from a pathologist. The grade is also important for the prognosis and recommended treatment options.