Tests to find out the stage of a skin cancer

Your doctor may carry out a number of tests to ‘stage’ your cancer.  But most basal cell cancers do not need staging because it is very rare for them to spread.  They will only be staged if they are very large.  Although it is rare for squamous cell cancers to spread, staging is more likely to be done for these because spread is possible.

The TNM staging system

Doctors use a staging system that is common to all cancers.  It is called the TNM system

The T indicates the size of the tumour    
The N shows whether the cancer has spread to the lymph nodes    
The M shows whether the cancer has spread to another part of the body

The number system

Once the TNM categories have all been decided, the information is put together to give a number stage of 0 to 4.  The lower the stage, the earlier the cancer has been diagnosed.  The stages of skin cancer are

Stage 0 (also called carcinoma in situ) – the cancer is only in the top layer of skin (the epidermis)    
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 to the tissues under the skin and possibly to nearby lymph nodes    
Stage 4 – the cancer has spread to another part of the body

 Carcinoma in situ

Squamous cell stage 0 is also called Bowen’s disease.  Carcinoma means there are cancer cells there.  But they are all contained in the area in which they started to develop and so are not able to spread or grow into surrounding areas of skin.  This means the carcinoma in situ is not really a fully-fledged cancer.  If it is not treated, it can develop into a squamous cell skin cancer.  

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