Staging is the process of determining details about your cancer, such as tumor size and if it has spread. The stage guides decisions about treatment.
TNM system describes the tumour extent (T) nodal involvement (N) and distant metastases (M). This defines a clinical classification (cTNM) or a pathological one (pTNM) which incorporates information derived from an excised tumour and any draining lymph nodes that are also removed or sampled. Details of this system are given in the TNM atlas which should be available and used wherever patients are
seen or results of investigation are correlated.
- T staging includes measurement of the tumour either clinically, by imaging techniques or by macroscopic examination of an excised specimen.
- Correct pathological T staging can only be assured if the pathologist receives a completely excised tumour with a rim of surrounding tissue.
The tumour should not be cut into or fixed except by the pathologist. Examination of the whole specimen is needed
to determine the highest grade of tumour , any vascular or lymphatic invasion or invasion of adjacent tissues. Spread into a body space such as the pleural or peritoneal cavity affects T stage as it changes prognosis.
- T0 implies no primary tumour.
- Categories T1–T4 indicate tumours of increasing size and/or involvement of lymphatic vessels or surrounding tissue. If it is impossible to ascertain size or extent of primary tumour, it is designated Tx.
- N classification describes whether there is lymph node involvement and if so, how many nodes are involved.
- M category indicates presence (M1) or absence (M0) of metastases to distant sites.
- Residual tumour after surgical excision is an important poor prognostic factor. Examination of resection margins assigns tumours to categories: R0, no residual tumour; R1, histologically detectable tumour at margins; and R2, macroscopic evidence of residual tumour. Where serum markers (S) convey important prognostic information, as in tumours of the testis, an S category has been introduced to the TNM system.
Grading is defined by degree of differentiation as:
- G1-resemblance to tissue of origin.
- G2- moderately well differentiated.
- G3- poorly differentiated.
- G4- undifferentiated tumours.