Grading and staging of bladder cancer

Grading

Grading refers to the appearance of the cancer cells under the microscope. The grade gives an idea of how quickly the cancer may develop. The most common grading system uses three grades:

• grade 1 (low grade)
• grade 2 (moderate grade)
• grade 3 (high grade)

Low grade means that the cancer cells look very much like normal bladder cells. They are usually slowly growing and less likely to spread. In high-grade tumours the cells look very abnormal. They are likely to grow more quickly and are more likely to spread.

Staging

The stage of a cancer describes how big the cancer is 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 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)

The diagram below shows different tumour sizes in the bladder.

• CIS (carcinoma in situ) means that cancer cells are in the inside layer of the bladder lining. However, they are a type that are quickly growing (grade 3) and are very likely to spread into the deeper layers of the bladder, unless they are effectively treated.
• Ta The cancer is a small area of cancer just in the bladder lining.
• T1 The cancer has started to grow into the connective tissue beneath the bladder lining.
• T2 The cancer has started to grow into the muscle of the bladder wall under the connective tissue layer.
• T3a The cancer has grown through the whole layer of muscle in the bladder
• T3b The cancer has grown through the muscle layer into the fat layer beneath.
• T4 The cancer has spread outside the bladder to the prostate, vagina or other organs in the pelvic area.

Stages Ta or T1 are called early or superficial bladder cancer.

Stages T2 or T3 are called invasive bladder cancer.

Stage T4 is called locally advanced bladder cancer. The cancer has spread into the tissue around the bladder.

Diagram showing different tumour sizes in the bladder

Lymph nodes (N)

The N refers to whether the cancer cells have spread into the lymph nodes close to the bladder. There are four lymph node stages. These are:

• N0 There are no cancer cells in any lymph nodes.
• N1 There are cancer cells in one lymph node smaller than 2cm across.
• N2 There are cancer cells in one affected lymph node larger than 2cm, but smaller than 5cm, or more than one node affected, but all of them smaller than 5cm across.
• N3 There are cancer cells in at least one affected lymph node larger than 5cm across.

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 bladder cancer spreads it is most likely to go to the bones, the lungs or the liver. If the cancer has spread it is called secondary or metastatic bladder cancer.