The most common system used to describe whether cancer has spread and if so, how far. It gives 3 key pieces of information: T refers to the size of the tumor N describes whether or not 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 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.