Genetics of Skin Cancer (PDQ®): Genetics - Health Professional Information [NCI] - Introduction
Function of the Skin
The skin has a wide variety of functions. First, the skin is an important barrier preventing extensive water and temperature loss and providing protection against minor abrasions. These functions can be aberrantly regulated in cancer. For example, in the erythroderma associated with advanced cutaneous T-cell lymphoma, alterations in the regulations of body temperature can result in profound heat loss. Second, the skin has important adaptive and innate immunity functions. In adaptive immunity, antigen-presenting cells engender a TH1, TH2, and TH17 response. In innate immunity, the immune system produces numerous peptides with antibacterial and antifungal capacity. Consequently, even small breaks in the skin can lead to infection. The skin-associated lymphoid tissue is one of the largest arms of the immune system. It may also be important in immune surveillance against cancer. Immunosuppression, which occurs during organ transplant, is a significant risk factor for skin cancer. The skin is significant for communication through facial expression and hand movements. Unfortunately, areas of specialized function, such as the area around the eyes and ears, are common places for cancer to occur. Even small cancers in these areas can lead to reconstructive challenges and have significant cosmetic and social ramifications.
Clinical Presentation of Skin Cancers
While the appearance of any one skin cancer can vary, there are general physical presentations that can be used in screening. BCCs most commonly have a pearly rim (see Figure 4) or can appear somewhat eczematous. They often ulcerate (see Figure 4). SCCs frequently have a thick keratin top layer (see Figure 5). Both BCCs and SCCs are associated with a history of sun-damaged skin. Melanomas are characterized by asymmetry, border irregularity, color variation, a diameter of more than 6 mm, and evolution (ABCDE criteria). (Refer to What Does Melanoma Look Like? on NCI's Web site for more information about the ABCDE criteria.) Photographs representing typical clinical presentations of these cancers are shown below.
Basal cell carcinomas
|Figure 2. Superficial basal cell carcinoma.||Figure 3. Nodular basal cell carcinoma.|
|Figure 4. Ulcerated basal cell carcinomas with characteristic pearly rim (right panel).|
Squamous cell carcinomas
|Figure 5. Squamous cell carcinomas.|
|Figure 6. Melanomas with characteristic asymmetry, border irregularity, color variation, and large diameter.|
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