Staging and grading of kidney cancer

Staging

The stage of a cancer describes its size and whether it has spread. Once your doctors know the stage of the cancer, they can decide on the most appropriate treatment for you. The most commonly used staging system for kidney cancer is called 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)

• T1a  The cancer is smaller than 4cm in size and limited to the kidney
• T1b The cancer is between 4cm and 7cm in size and is limited to the kidney
• T2 The cancer is larger than 7cm but is still limited to the kidney.
• T3 The cancer is growing into the adrenal gland OR into the fat around the kidney but not beyond the fibrous tissue (Gerota’s fascia) OR into one or both large blood vessels close to the kidney (renal artery and renal vein).
• 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. There are three lymph node stages. These are:

• N0 There are no cancer cells in any lymph nodes.
• N1 There are cancer cells in one lymph node.
• N2 There are cancer cells in two or more lymph nodes

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

Metastases (M)

If the cancer cells have not spread, this is described as M0.

If cancer cells have spread to other parts of the body it is said to be M1. 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 is called secondary or metastatic kidney cancer.

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 smaller than 7cm and is limited to the kidney. There is no spread to lymph nodes or other organs.
• Stage 2 The cancer is larger than 7cm and is limited to the kidney. There is no spread to lymph nodes or distant organs.
• Stage 3 The cancer has begun to spread outside the kidney. It may have spread into the adrenal gland, which sits on top of the kidney, OR to one of the large blood vessels close to the kidney (the renal vein or the vena cava) OR to only one lymph node OR into the fat that surrounds the kidney.
• Stage 4 The cancer has grown through the fibrous tissue outside of the kidney, and/or has spread to two or more lymph nodes and/or has spread to other organs.

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 cancer such as a grade 4 cancer.