The TNM Staging System  With this type of staging system, a cancer is given a particular letter along with a corresponding number that indicates size, has it spread to the lymph nodes and beyond.
Here is a breakdown of this staging system and how it works:   T: The T stands for tumor size.
The different stages within the T group are:

• TX: The tumor can not be assessed.
  
• T0: The tumor can not be found
• Tis: Means that the tumor has not spread, this is also known as "in situ"
• T1-T4: describes the various size of tumors as well as the degree to which they have spread

  N: The N stands for nodes as in lymph nodes.
This staging determines whether or not the cancer has spread into the nodes.

• NX: The nearby lymph nodes can not be accessed.
  
• N0: No evidence of cancer in the nearby lymphnodes.
  
• N1-N4: Describes which lymphnodes the cancer has moved to which indicates how far it is spreading.
  

  M: The M stands for metastasized.
This will indicate how much cancer has spread into other tissues and organs from the lymph nodes.

• M0: Indicates that the cancer has NOT spread to other sites and distant organs
• M1: Indicates that the cancer HAS spread into other sites and to distant organs

Once the TNM staging is has been determined, these numbers are then evaluated to determine what "stage" of cancer someone has.
These are described as stages I-IV with IV having the worst prognosis and survival rate.