Key points
- Stage = how far the cancer has spread; grade = how abnormal the cells look.
- T is the primary tumour, N the regional nodes, M distant metastasis.
- A p prefix means pathological staging; yp means after neoadjuvant treatment.
- R0 means no tumour at the margin: the aim of curative surgery.
TNM
The UICC/AJCC TNM system (8th edition) describes a solid cancer in three parts:
- T: size or depth of the primary tumour (Tis, T1–T4).
- N: spread to regional lymph nodes (N0–N3).
- M: distant metastasis (M0 or M1).
An X means it cannot be assessed. Prefixes say how it was staged: c clinical (examination and imaging), p pathological (the resected specimen), yp pathological after neoadjuvant treatment, r recurrence.
Example: colon cancer
| T | Depth |
|---|---|
| T1 | Into the submucosa |
| T2 | Into the muscularis propria |
| T3 | Through the muscularis propria into pericolorectal tissue |
| T4a / T4b | Through the visceral peritoneum / into adjacent organs |
N1 = 1–3 regional nodes; N2 = 4 or more. At least 12 nodes should be examined for accurate staging. T and N combine into stage groups I–IV; stage IV means distant metastasis. A pT3 N1 M0 colon cancer is stage III and is usually offered adjuvant chemotherapy.
Grade is not stage
Grade describes how differentiated the cells are: G1 well, G2 moderately, G3 poorly differentiated. A small, poorly differentiated tumour has a low stage but a high grade. Both affect prognosis.
The resection margin: R status
- R0: no tumour at the margin under the microscope. The goal of curative surgery.
- R1: microscopic tumour at the margin.
- R2: visible tumour left behind.
Performance status
| ECOG | The patient |
|---|---|
| 0 | Fully active, no restriction |
| 1 | Cannot do strenuous activity but can do light work |
| 2 | Walking and self-caring, up and about more than half of waking hours, but cannot work |
| 3 | Limited self-care, in bed or chair more than half of waking hours |
| 4 | Completely disabled, confined to bed or chair |
| 5 | Dead |
Why it matters
Stage, grade, margin and performance status together decide what the MDT can offer. A fit patient (ECOG 0–1) with stage III disease is treated very differently from a frail patient (ECOG 3) with the same tumour.
Frequently asked questions
What does TNM stand for?
T is the size or depth of the primary tumour, N is spread to regional lymph nodes, and M is distant metastasis.
What is the difference between tumour stage and grade?
Stage describes how far the cancer has spread. Grade describes how abnormal (poorly differentiated) the cells look under the microscope.
What is an R0 resection?
An operation in which no tumour is seen at the resection margin under the microscope. R1 means microscopic tumour at the margin; R2 means visible tumour was left behind.
What is ECOG performance status?
A 0 to 5 scale of how active a patient is, from 0 (fully active) to 4 (completely disabled) and 5 (dead). It guides what treatment a patient can tolerate.
Further reading
- Brierley JD, Gospodarowicz MK, Wittekind C (eds). TNM Classification of Malignant Tumours, 8th edition. UICC / Wiley-Blackwell, 2017.
- Oken MM, et al. Toxicity and response criteria of the Eastern Cooperative Oncology Group. Am J Clin Oncol 1982;5:649–55.