The short answer
TNM is the most common way to stage cancer. T describes the size of the tumor, N whether it has reached lymph nodes, and M whether it has spread to distant parts of the body.
TNM stands for Tumor, Node, and Metastasis.
T describes the size and extent of the main tumor.
N describes whether cancer has reached nearby lymph nodes.
M describes whether cancer has spread to distant organs.
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The full explanation.
The most common staging system
Most solid cancers are staged using the TNM system. The three letters stand for Tumor, Node, and Metastasis — the three questions that most affect how a cancer is treated and what to expect.
What each letter measures
T describes the size and extent of the main tumor, usually with a number from 1 to 4 (higher means larger or more deeply grown). N describes whether cancer has reached nearby lymph nodes and how many. M describes whether the cancer has spread to distant parts of the body, written as M0 (no distant spread) or M1 (distant spread present).
From letters to a stage
Doctors combine the T, N, and M categories — using rules tailored to each cancer type — into an overall stage. This is often written as stage 0 through stage IV, with higher stages meaning more extensive disease.
Why it matters
Staging helps predict outlook and choose treatment, and it gives everyone on the care team a shared, precise way to describe the cancer. If your report lists a TNM combination, your doctor can explain what it means for your specific cancer.
Words to know
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Common questions
▸What does each letter mean?
T is for the size and extent of the main tumor, N is for spread to nearby lymph nodes, and M is for metastasis, meaning spread to distant parts of the body.
▸What do the numbers after the letters mean?
Higher numbers mean more extent — for example, T1 is a smaller tumor than T3, and N0 means no lymph node involvement while N1 or higher means some.
▸How does TNM become a stage?
The T, N, and M categories are combined, using rules specific to each cancer type, into an overall stage, commonly written as stage 0 through IV.
▸Why does staging matter?
Stage helps predict outlook and guides treatment. It also lets doctors compare results and describe a cancer clearly to the whole care team.
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