Once a patient has been diagnosed with cancer, the physician will determine the degree of spread and aggressiveness of the tumor: the stage and grade of disease. The stage is the degree of spread of the tumor: Doctors often use the TNM system for staging. TNM stands for 'tumor, node, metastasis'. Important aspects of the staging of cancer are:


The grade of a cancer relates to its appearance under the microscope. Low-grade malignancy often has a better prognosis than a high-grade malignancy. High grade is characterized by a highly abnormal appearance of the cancer cells

There is no standard treatment for cancer; it will depend on the unique situation. If a cancer is confined to a single site, surgical removal is often (but not always) the first step. After this, the additional therapy depends on the estimated aggressiveness of the cancer. Doctors judge the aggressiveness of a cancer by a number of patient- and tumor characteristics, including the grade of the cancer as determined by microscopic evaluation (see figure). The estimated aggressiveness of the cancer determines the subsequent course of treatment. If the risk of metastasis is judged to be low, the doctor may decide not to give additional (chemo)therapy (adjuvant therapy); if the tumor is considered to be highly malignant, adjuvant (chemo)therapy may be required to kill remaining tumor cells that may already have disseminated from the primary tumor site.

This additional (chemo)therapy has been shown to improve survival for many forms of cancer, but also has undesired side effects. The choice to give additional therapy to a patient is therefore a difficult but important decision to make and varies from patient to patient. New available diagnostic tools based on microarray tecnology can help doctors to determine how aggressive a cancer is and hence to choose the optimal therapy for any given patient.