A staging system is a clinical evaluation, based on the best possible estimate of the extent of the disease prior to treatment.
N describes the extent of the spreading to the lymph nodes. M is an indicator of metastasis or spreading of the cancer to other organs.
The physician needs to know the extent, or stage, of the disease so he or she can determine the best course of treatment.
Understanding staging helps both patient and physician make an appropriate treatment decision.
Patients should ask their physicians to explain staging in a way that they can easily understand.