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Melanoma in situ (stage 0)

Find out what melanoma in situ (stage 0) means and about treatment options.

Melanoma in situ is also called stage 0 melanoma. It means there are cancer cells in the top layer of skin (the epidermis). The melanoma cells are all contained in the area in which they started to develop and have not grown into deeper layers of the skin.

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 invasive cancer.

TNM stages

The TNM staging system stands for Tumour, Node, Metastasis.

  • T describes the size of the tumour
  • N describes whether there are any cancer cells in the lymph nodes
  • M describes whether the cancer has spread to a different part of the body

In the TNM staging system melanoma in situ is the same as Tis, N0, M0.


The stage of your cancer helps your doctor to decide what treatment you need. Treatment also depends on:

  • where the cancer is
  • other health conditions

Surgery is the main treatment. Doctors remove the abnormal mole and a small area of surrounding skin. You may need a second operation to remove a larger area of healthy tissue around where the melanoma in situ was. This is called a wide local excision. As long as the doctors are sure they removed enough tissue, this is all the treatment you need.  

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 period of weeks.

Last reviewed: 
12 Nov 2015
  • Melanoma assessment and management
    National Institute for Health and Care Excellence (NICE), July 2015

  • Cancer: Principles and practice of oncology (10th edition)
    VT De Vita, TS Lawrence and SA Rosenberg
    Lippincott, Williams and Wilkins, 2015   

  • TNM Classification of Malignant Tumours (7th edition)
    International Union Against Cancer   
    L.H. Sobin, M.K. Gospodarowicz, Ch. Wittekind
    John Wiley & Sons, Hoboken, New Jersey, 2009

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