Structure of the skin
The outer layer of skin is called the epidermis and is made primarily of specialized cells called keratinocytes but has several other minor cell populations. The bottom layer is formed of basal keratinocytes abutting the basement membrane. The basement membrane is formed from products of keratinocytes and dermal fibroblasts, such as collagen and laminin, and is an important anatomical and functional structure. Additionally, in the epidermal compartment, melanocytes distribute singly along the basement membrane and can transform into melanoma. Melanocytes are derived from neural crest cells and migrate to the epidermal compartment near the eighth week of gestational age. Langerhans cells, or dendritic cells, are a third cell type in the epidermis and have a primary function of antigen presentation. These cells reside in the skin for an extended time and respond to different stimuli, such as ultraviolet (UV) radiation or topical steroids, which cause them to migrate out of the skin.
Who is at risk for melanoma?
Anyone can get melanoma, as it affects both men and women. Genetics plays a role in approximately five percent of patients with melanoma. Although melanomas may be found in places on the body never exposed to the sun, the major risk factor is cumulative exposure to sunlight which is why the majority of melanomas are diagnosed after the fifth decade (see graph: Age at Diagnosis). Although dark skin does not burn in the sun as easily as fair skin, everyone is at risk for skin cancer. Even people who don't burn are at risk for skin cancer. It doesn't matter whether you consider your skin is light, dark, or somewhere in between. Sunlight causes damage to the skin through ultraviolet, or UV rays (they make up just one part of sunlight). Two parts of UV, UVA and UVB, can both cause damage to skin (2).
What does Melanoma look like?
A change on the skin is the most common sign of skin cancer. This may be any new growth on the skin, a sore that doesn't heal, or a change in an old growth. Melanomas are typically characterized by asymmetry, border irregularity, color variation, a diameter of more than six mm, and evolution (ABCDE criteria).
Treatment and Prevention
Although wide surgical excision remains the mainstay of treatment (see graph: First Course Surgery), the best treatment is still prevention. Avoiding unnecessary exposure to sunlight and wearing protective clothing will prevent most of these cancers. Regular sunscreen use may reduce the risk of developing melanoma, according to results of a randomized controlled trial that was reported December 6, 2010 in the Journal of Clinical Oncology. The trial is the first prospective, randomized study to investigate the link between sunscreen use and melanoma. The study concluded that among adults age 25 to 75 years, regular application of SPF 15+ sunscreen in a five-year period appeared to reduce the incidence of new primary melanomas for up to 10 years (3).
References: 2.) http://www.cancer.gov/clinicaltrials/results/summary/2010/sunscreen-melanoma2010