When we talk of staging we are talking of how aggressive the cancer is and how much of an affect it has already had. This process is essential, as it will allow the team treating the patient to decide on the most appropriate treatment for the individual, and also allows accurate data collection and research on this type of cancer.
Doctors grade cancers to indicate how quickly or slowly a cancer is likely to grow and spread using the Fuhrman nuclear grading system. When removed, the tumour will be sent to the histopathology laboratory to be looked at under the microscope. By looking at certain features of the cells the cancer can be graded as low, intermediate or high grade.
- Grade 1 or low-grade cells are usually slow growing, look quite similar to normal cells, tend to be less aggressive and are less likely to spread.
- Grade 2 or intermediate grade cells grow more quickly, look abnormal, are moderately aggressive and could spread.
- Grade 3 or high-grade cells are likely to grow more quickly, look very abnormal, tend to be more aggressive and are more likely to spread.
- Grade 4 or high-grade cells look very abnormal, grow very quickly, are extremely aggressive and are very likely to spread.
There are several types of renal cancer identifiable under the microscope, and these different types can have varying prognostic values:
| Cell Type | Feature | Growth Pattern | Cell of Origin |
| Clear Cell | Most Common | Acinar or sarcomatoid | Proximal tubule |
| Chromophilic | Bilateral and multifocal | Papillary or sarcomatoid | Proximal tubule |
| Chromophilic | Indolent course | Solid, tubular, or sarcomatoid | Cortical collecting duct |
| Oncocytic | Rarely metastasise | Tumour nests | Cortical collecting duct |
| Collecting duct | Very aggressive | Papillary or sarcomatoid | Medullary collecting duct |
Staging is used to describe how big a cancer is and how far it has already spread. The TNM system is a common system used for staging tumours:
T (tumour) plus a number indicates the size of the primary tumour and how far it has grown locally
N (nodes) plus a number indicates that the cancer has spread to nearby lymph nodes
M (metastases) plus a number refers to places elsewhere in the body where the cancer has spread.
The TNM staging for renal cancer is as follows:
Primary tumour (T)
TX – Primary tumour cannot be assessed
T0 – No evidence of primary tumour
T1 – Tumour 7 cm or smaller in greatest dimension, limited to the kidney
T2 – Tumour larger than 7 cm in greatest dimension, limited to the kidney
T3 – Tumour extends into major veins or invades adrenal gland or perinephric tissues but not beyond the Gerota fascia
T3a – Tumour invades adrenal gland or perinephric tissues but not beyond the Gerota fascia
T3b – Tumour grossly extends into the renal vein(s) or vena cava below the diaphragm
T3c – Tumour grossly extends into the renal vein(s) or vena cava above the diaphragm
T4 – Tumour invading beyond the Gerota fascia
Regional lymph nodes (N) – Laterality does not affect the N classification
NX – Regional lymph nodes cannot be assessed
N0 – No regional lymph node metastasis
N1 – Metastasis in a single regional lymph node
N2 – Metastasis in more than 1 regional lymph node
Distant metastases (M)
MX – Distant metastases cannot be assessed
M0 – No distant metastases
M1 – Distant metastases
Another staging classification which is sometimes used for renal cancer is a number system; the cancer is simply said to be stage 1, 2, 3 or 4 (or stage I, II, III, or IV). Again, the stages reflect how large the primary tumour has become, and whether the cancer has spread to lymph nodes or other areas of the body. A stage 4 tumour is often referred to as an ‘advanced’ cancer. The number system used for renal cancer is as follows:
Stage 1 The cancer is confined to the kidney and is less than 7cm in size