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A Guide to Melanoma in Situ

written by: Sarah Mitchell • edited by: Diana Cooper • updated: 2/13/2011

While skin cancer is on the rise, few understand the basic anatomy of the epidermis - the layer of skin afflicted with this disease - and the stages of malignant melanoma. Learn about malignant melanoma in situ, the tiers within the epidermis and treatment options available for sufferers.

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    An Explanation of Malignant Melanoma in Situ

    It is not surprising that the skin is the largest organ of the body. After all, it covers the human body from head to toe. It is responsible for providing the body with internal protection, body temperature regulation, and water and vitamin storage.

    Skin consists of three layers, each with its own function. One of these three layers includes the epidermis, the outer layer of skin. There are three tiers of cells within this external layer: squamous and basal cells, and melanocytes. With respect to their location within the epidermis, the squamous cells are found in the top tier, basal cells are in the middle tier, and melanocytes are in the bottom tier.

    These three cell types are commonly afflicted with cancer: squamous cell and basal cell carcinomas, and melanoma, with melanoma being the least rare but the most deadly. We are going to concentrate on the bottom cell tier, the melanocytes.

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    Understanding Melanoma in Situ

    Melanocytes play two important roles: melanin production – responsible for the body’s natural pigmentation – and skin protection from UV damage. When the skin has been overexposed to UV light, a dark coloring is produced and can be visibly seen. Also known as a tan, this dark pigment is a sign of skin damage, not a healthy glow.

    Human genetics and UV damage are the two common causes of cell mutation today. It is when melanocytes transform to an abnormal state that a patient is then diagnosed with malignant melanoma in situ, also known as stage 0 melanoma. Melanoma in situ tumors are classified as Tis, indicating tumor in situ. In situ is a Latin term simply meaning “in place.”[1]

    Malignant melanoma in situ solely affects the epidermis and is, therefore, non-invasive. It has not migrated to other parts of the body, such as the lymph nodes.

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    Melanoma in Situ Treatment Options

    Fortunately, stage 0 melanomas are, most often, easy to treat because they are the least invasive when compared to the other stages of melanoma. Typically, all that is required is excision of the affected cells and surrounding healthy tissue; this type of outpatient treatment is often found to be successful. Of note, however, repeated surgical treatment may be required until all margins of the area in concern are clear.

    Excision may not be ideal in the cases of malignant melanoma in situ of the head and neck due to the risk of disfiguration. Researchers at the University of Connecticut Health Center and School of Medicine have reported that the use of the 5% strength topical cream, imiquimod, healed patients suffering from facial melanoma in situ. Thus, imiquimod was found to be an effective treatment without the normal disfiguring results of excision.

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    Sources:

    1. Melanoma Center website. Stage 0 Melanoma: Melanoma in Situ. Accessed November 21, 2010. [1]
    2. Cancer.gov website. Stages of Melanoma. Accessed November 20, 2010.
    3. Cancer.gov website. Stage 0 Melanoma. Accessed November 20, 2010.
    4. PubMed website. Successful Treatment of Malignant Melanoma in Situ with Topical 5% Imiquimod Cream. Accessed November 21, 2010.
    5. Cancer.gov website. Skin Cancer Screening (PDQ) Patient Version. Accessed November 21, 2010.