Staging of skin cancers

Knowing the extent of the cancer helps the doctors to decide on the most appropriate treatment. Most people with basal cell cancers do not need to have tests to find the stage of the cancer, as it is very rare for them to spread beyond the initial area of skin. Tests will only be done if the cancer is very large.

Although it is rare for squamous cell cancers to spread, tests to find the stage may be done because in some people they may spread.

A commonly used staging system is outlined below:

• Stage 0 is also called carcinoma in situ. Carcinoma in situ means that cancer cells are present, but they are all contained in a small area in the top layer of skin (the epidermis). They have not started to spread or grow into deeper layers of skin. Squamous cell stage 0 is also called Bowen's disease. If it is not treated, it can develop into a squamous cell skin cancer.
• Stage 1 The cancer is less than 2cm across and has not spread
• Stage 2 The cancer is more than 2cm across and has not spread
• Stage 3 The cancer has spread into the tissues under the skin and possibly to nearby lymph nodes
• Stage 4 The cancer has spread to another part of the body. This very rarely occurs with either squamous or basal cell cancers of the skin.

TNM staging system

Another staging system known as the TNM system is commonly used. This can give more precise information about the extent of the cancer.

• T describes the size of the tumour.
• N describes whether the cancer has spread to the lymph nodes.
• M describes whether the cancer has spread to another part of the body (secondary or metastatic cancer).