TNM classification
From Ganfyd
The TNM classification system is used to grade malignant tumours. It has been developed and maintained by the International Union Against Cancer (UICC) and is used as a global method to classify the majority of types of malignant disease in the human body. It is also used by the American Joint Committee on Cancer (AJCC).
The aim of the TNM classification is to adopt a global standard to ensure that adequate treatment can be planned, than an accurate prognosis can be given, and that there is a uniform system to evaluate the results of treatment. This purported advantage is somewhat limited by intermittent revisions in the staging system as newer research data is incorporated into prognosis and survival.
The TNM system provides useful prognostic information for most tumours, but is less useful in some types of cancer. For breast cancer, although the TNM system does include an option for grade (G) based on the commonly used Nottingham prognostic index, grading is not otherwise part of the core TNM components. The justfication for leaving this out is that the variation in rapidity of fixation can result in significant differences in grading making it difficult for it to be reliably reproducible. Furthermore, TNM does not yet incorporate hormonal status and other molecular profiles known to be important in prognosis, e.g. oestrogen/progesterone receptor and Her2 status in breast cancer.
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Outline of TNM classification
Each tumour has its own TNM classification. The values given in parenthesis give a range of what can be used for all cancer types. Not all cancers use this full range.
Prefixes
Not all tumours are described with a prefix.
- a: Autopsy staging.
- c: Clinical staging. Absence of a prefix implies that the tumour is clinically staged.
- p: Pathological staging. The tumour has been histologically confirmed.
- r: Recurrent tumour. Re-staging following a disease-free interval.
- y: Neoadjuvant staging. The tumour is stages after neoadjuvant therapy.
TNM staging
All tumours using the TNM classification are given a TNM description.
- T(x,is,0,1,2,3,4): Describes the size of the tumour. Tx means the tumour cannot be assessed. Tis is a tumour in situ.
- N(x,0,1,2,3): Describes the lymph node status. TX means that nodal status cannot be assessed.
- M(x,0,1): Describes the presence of metastatic spread. Mx means that metastatic spead cannot be assessed.
Other parameters
These parameters are sometimes used.
- G (1-4): This is sometimes used to describe the grade of the tumour:
- GX = Cannot be assessed
- G1 = Well differentiated
- G2 = Moderately differentiated
- G3 = Poorly differentiated
- G4 = Undifferentiated
- L (0-1): Lymphatic vessel invasion:
- LX = Cannot be assessed
- L0 = No lymphatic vessel invasion
- L1 = Lymphatic vessel invasion
- V (0-2): Venous invasion:
- VX = Cannot be assessed
- V0 = No venous invasion
- V1 = Microscopic venous invasion
- V2 = Macroscopic venous invasion
- Pn (0-1): Perineural invasion
- PnX = Cannot be assessed.
- Pn0 = No perineural invasion
- Pn1 = Perineural invasion
- R (0-2): This is sometimes used to describe resection boundries after an operation, where:
- RX = Presence of residual tumour cannot be assessed
- R0 = No residual tumour
- R1 = Microscopic residual tumour
- R2 = Macroscopic residual tumour
An example of the TNM classification
For example, a laryngeal carcinoma that has been histologically confirmed as a squamous cell carcinoma, was confined to the glottic, fixed a vocal cord, involved a single neck node of 2 cm on the same side and was not associated with any metastases could be described as a pT3N1M0 squamous cell carcinoma of the glottis.
