Cancer Stage and TNM Decoder

Enter the T, N and M from your report for breast, colorectal, lung, prostate cancer or melanoma and see the stage group, what each letter and number means, and what to ask next.

This decoder shows how TNM categories are grouped into stages in the UICC/AJCC 8th edition. It cannot stage your cancer: your team assigns the stage from imaging, biopsies and surgery, and several types use extra factors. Use it to understand a stage you have been given, not to work one out.

Talk to your oncology team, GP or a registered dietitian before acting on any number here. They know your history; a calculator does not.

Decode your TNM

Choose the cancer type, then the T, N and M written on your report. The small letters before them (c, p, y, r) are explained below.

Stage group

Small letters before the T, N or M

c: Clinical stage: worked out before treatment from examination, imaging and biopsies.
p: Pathological stage: worked out after surgery from the removed tissue, so it is usually more accurate than the clinical stage.
y: Stage assessed after neoadjuvant treatment (chemotherapy, radiotherapy or hormone therapy given before surgery); ypT0 means no tumour was left.
r: Stage of a recurrence, assigned when the cancer comes back after a disease-free interval.

How this is calculated

The stage group comes from the grouping rules of the UICC/AJCC TNM Classification, 8th edition (2017), for the chosen cancer type; breast cancer uses the anatomic stage, prostate cancer adds PSA and Grade Group, melanoma uses the clinical grouping.

The rules are written into this page from the public NCI PDQ stage information for each cancer type; the AJCC and UICC own the classification itself and publish the full manuals.

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What TNM staging is and who defines it

Almost every solid cancer is staged with the TNM system, maintained jointly by the Union for International Cancer Control (UICC) and the American Joint Committee on Cancer (AJCC). T describes the primary tumour, N the regional lymph nodes and M distant spread. Each cancer type has its own definitions for the numbers, and its own table turning a T, N and M combination into a stage group from 0 to IV.

The stage group is the shorthand your team uses to choose treatment, estimate prognosis and compare your situation with the evidence from clinical trials. It is also what most guidelines are organised around, which is why the same word, stage III, can mean quite different things in breast cancer and in lung cancer.

Clinical versus pathological stage

A clinical stage (cTNM) is set before treatment from examination, imaging and biopsies. A pathological stage (pTNM) is set after surgery, when the pathologist measures the tumour and counts the nodes under the microscope; it is usually more accurate, and it can move the stage up or down. If you had chemotherapy, radiotherapy or hormone therapy before surgery, the letter y marks the post-treatment stage (ypTNM), and ypT0 ypN0 means no living tumour was found, a complete response.

Both stages stay on your record. When people say their stage changed, it is usually the pathological stage refining the clinical one, not the cancer itself changing.

What the stage does not tell you

Grade: how abnormal the cells look and how fast they are likely to grow. It comes from the pathology report, not the TNM.
Biomarkers: receptors and mutations such as ER, PR, HER2, KRAS, EGFR, PD-L1 or MSI often matter more for choosing drugs than the stage does.
Response to treatment: two people with the same stage can respond very differently.
Your own prognosis: survival figures by stage are averages from large groups diagnosed years ago; they do not predict one person.
Performance status, age and other illnesses, which shape which treatments are safe for you.

Editions change: 8th and 9th

The TNM classification is revised every few years as evidence accumulates. The 8th edition took effect in 2017 and is what this page implements. A 9th edition for lung cancer came into use in 2025, splitting N2 and M1c into finer categories and moving a few stage groups; other cancer types will follow over the coming years. Your report should state the edition used, and a stage set under one edition is not simply comparable with one set under another.

Other letters and symbols on the staging line

(sn) after N means the nodes were assessed by sentinel node biopsy; (f) means by fine-needle aspiration or core biopsy.
(mi) marks micrometastases; (i+) marks isolated tumour cells found only with special stains.
(m) after T, as in pT2(m), means more than one tumour in the same organ.
R0, R1 and R2 describe the surgical margins: no tumour at the edge, microscopic tumour at the edge, visible tumour left behind.
G1 to G4 is the grade; L and V record invasion of lymphatic or blood vessels; Pn records perineural invasion.

Questions to ask your oncology team

Bring the result with you and ask:

Is this a clinical or a pathological stage, and could it change after surgery?
Which edition of TNM was used?
What does this stage mean for the goal of my treatment: cure, long-term control or symptom control?
Which other results (grade, receptors, mutations) matter as much as the stage for my treatment plan?
Are there clinical trials for my stage and type?
Who can I contact between appointments if I have questions about my results?

Sources and review

Written by the Beat Cancer EU editorial team using the primary sources below, which are also the formulas this tool implements. Last reviewed: September 14, 2026.

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