Melanoma skin cancer in situ (stage 0)
Melanoma skin cancer in situ is also called stage 0 melanoma skin cancer. This means there are cancer cells only in the top layer of skin (the epidermis).
Surgery is the main treatment for melanoma in situ.
What is an in situ cancer?
Some doctors call in situ cancers pre cancer. In a way, they are. Although the cells are cancerous, they cannot spread to other parts of the body, so in situ cancers are not a cancer in the true sense. But if they are not treated, in situ cancers can develop into 
.
What is melanoma in situ?
Melanoma skin cancer starts in cells called melanocytes. Melanoma in situ means the cancer cells are all contained in the epidermis where they started. They have not grown deeper into the skin.
Stage 0 is part of the number staging system. This goes from stage 0 to stage 4. It tells you how thick the melanoma is and if the cancer cells have spread to the or other parts of your body. Your doctor might also use the TNM staging system for melanoma skin cancer.
TNM stages
Doctors also use another staging system for melanoma called the TNM staging system. It stands for Tumour, Node, Metastasis.
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T describes the size of the tumour
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N describes whether there are any cancer cells in the lymph nodes
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M describes whether the cancer has spread to a different part of the body
The TNM staging system describes the cancer in detail. The number staging system puts these details together to give an overall stage. This can be easier to understand.
In the TNM staging system melanoma in situ is the same as Tis, N0, M0.
Treatment for melanoma in situ
The stage of the cancer helps your doctor decide what treatment you need. Treatment also depends on:
- where the melanoma is
- your general health and level of fitness
Surgery
Surgery is the main treatment for melanoma in situ. After your diagnosis, you usually have an operation to remove 0.5cm or more of healthy tissue around where the melanoma was. This is called a .
If your doctor is sure they removed enough tissue, this is all the treatment you need.
Imiquimod cream
Surgery can cause scarring and some people may not be well enough to have an operation. Instead of surgery, you might have treatment with a cream called imiquimod. You put imiquimod on the affected area, over a number of weeks. Your doctor, nurse or pharmacist will tell you how long to use it for.
You might have another skin biopsy after you have had imiquimod treatment to see if it has worked.
