Staging and grading of kidney cancer

Staging

The most commonly used staging system for kidney cancer is the TNM system:

T refers to the tumour size.

N refers to whether lymph nodes are affected.

M refers to whether the cancer has spread to other parts of the body (metastases).

Tumour size (T)

T1 The cancer is no larger than 7cm in size and is inside the kidney.

T1a The cancer is no larger than 4cm and is inside the kidney.

T1b The cancer is between 4–7cm and is inside the kidney.

T2 The cancer is larger than 7cm but is inside the kidney.

T2a The cancer is between 7–10cm and is inside the kidney.

T2b The cancer is larger than 10cm and is inside the kidney.

T3 The cancer has spread into the fat around the kidney but not beyond the fibrous tissue (Gerota's fascia, see diagram below) OR into major veins close to the kidney (vena cava and renal vein).

T3a The cancer extends into the renal vein or the fat around the kidneys but not the fibrous tissues (Gerota’s fascia).

T3b The cancer extends into part of a large blood vessel called the vena cava, which is below the diaphragm.

T3c The cancer extends into the part of the large blood vessel (the vena cava) which is above the diaphragm and it is growing into the wall of the blood vessel.

T4 The cancer has spread outside the fibrous envelope of tissue (Gerota’s fascia) that surrounds the kidney.

Lymph nodes (N)

The N refers to whether the cancer cells have spread into the lymph nodes close to the kidney.

N0 There are no cancer cells in any lymph nodes.

N1 There are cancer cells in one or more lymph nodes.

If the cancer cells have spread to the lymph nodes, the nodes are said to be positive.

Metastases (M)

M0 The cancer cells have not spread to other parts of the body.

M1 The cancer cells have spread to other parts of the body. If kidney cancer spreads it is most likely to go to the bones, the lungs, the liver or the brain. If the cancer has spread it’s called secondary or metastatic kidney cancer.

 

Number staging

The T, N and M stages may be grouped together to give an overall stage for the cancer from 1–4.

Stage 1 The cancer is 7cm or less and is inside the kidney. There is no spread to lymph nodes or other organs.

Stage 2 The cancer is larger than 7cm and inside the kidney. There is no spread to lymph nodes or distant organs.

Stage 3

• The cancer is inside the kidney but has spread to one or more lymph nodes.
• The cancer has begun to spread outside the kidney – it may have spread into one of the major veins close to the kidney (the renal vein or the vena cava) OR into the fat that surrounds the kidney. It may or may not have spread to one or more lymph nodes.

Stage 4

• The cancer has grown through the fibrous tissue outside of the kidney. It may or may not have spread to one or more lymph nodes.
• The cancer has spread to other parts of the body. It can be any size, and may have grown into the tissue outside the kidney.

Grading

Grading refers to the appearance of the cancer cells under the microscope. The grade gives an idea of how the cancer may behave. The Fuhrman system is the most common grading system for kidney cancer. It goes from 1–4; the higher the number, the more abnormal the cells look. A grade 1 cancer will usually grow more slowly and be less likely to spread than a higher grade, such as a grade 4 cancer.