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The most commonly used system to stage cancers. The TNM staging system uses 3 key pieces of information.

• T refers to the size of the tumor
• N describes whether the cancer has spread to nearby lymph nodes, and if so, how many
• M shows whether the cancer has spread (metastasized) to other organs of the body

Letters or numbers after the T, N, and M give more details about each of these factors. To make this information clearer, the TNM descriptions can be grouped together into a simpler set of stages, labeled with Roman numerals (usually from I to IV). In general, the lower the number, the less the cancer has spread. A higher number means a more serious cancer. Also called AJCC staging system.