What do the letters T, N, and M mean in the TNM cancer staging system?

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Precancerous growth in a human colon — cancer View through an endoscope of a polyp, a benign precancerous growth projecting from the inner lining of the colon.

The TNM staging system is an internationally recognized method used to describe the extent and spread of cancer within a patient's body. The letters represent the following criteria:1

T: Refers to the size and extent of the primary tumor.1
N: Indicates the presence and extent of lymph node involvement or metastases.1
M: Denotes whether the cancer has spread, or metastasized, to distant parts of the body.1

By evaluating these factors, clinicians can determine the stage of the disease, which is essential for predicting tumor behavior, establishing a prognosis, and selecting the most appropriate treatment approach.1