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INTRODUCTION

KEY POINTS

  • Primary carcinoma of the skin is the most common form of cancer diagnosed in the United States, but the incidence in people with skin of color is reported as rare.

  • Most squamous cell carcinomas (SCCs) in people with skin of color occur in non–sun-exposed areas; however, when SCC does occur in a sun-exposed area, the anatomic distribution is similar to that in Caucasians.

  • SCC that occurs in sun-exposed skin has its origin in loss of the organized control of epidermal keratinocyte differentiation secondary to DNA damage as a direct result of ultraviolet light.

  • The factors that are responsible for developing skin cancers in non–sun-exposed areas are unknown.

  • Areas of chronic inflammation, chronic ulceration, and scarring are predisposed to the development of SCC.

Most of the information regarding nonmelanoma skin cancer in skin of color reported in the U.S. literature focuses on disease incidence primarily in the African American population. The information is reported in the context of case reports or incidence studies from small groups. Information regarding the incidence of nonmelanoma skin cancer in other racial or ethnic groups, including Native Americans, Asians, and Hispanics, is sparse. The groups of people that constitute people with darker skin of color have grown considerably. Considering the changing demographics of the United States, to keep meaningful and accurate data, prospective research should recognize the population changes that are occurring. Larger population studies should be performed involving people with skin of color, which represents multiple ethnic and racial groups. U.S. Census information predicts that by the year 2050, the Caucasian population will be less than 50% of the total population. This figure will continue to decline during the ensuing decades of continued immigration and assimilation in the United States.

MELANIN AND PHOTOPROTECTION

The reduced incidence of skin cancer in people with skin of color has been attributed to various factors. Montagna and Carlisle1 have studied racial differences in melanin activity, fibroblast activity, and hair distribution on skin that may help to account for the reduced frequency of skin cancer in people with skin of color. Melanin, which is synthesized in melanosomes, is a known photoprotector in both animals and humans. It essentially creates a shield from the sun by absorbing and deflecting ultraviolet (UV) light.2 The basal cell layer melanocyte is responsible for the production of melanin. There is no racial difference in the number of melanocytes.3 The number of melanocytes may vary from one individual to the other and in different anatomic regions.4 The variations in color that can be seen in individuals are attributed to the size and aggregation of melanosomes in the melanocyte and keratinocyte. The increased number and dispersion of stage IV melanosomes provide a measure of photoprotection.2 Racial differences, as well as sun exposure, can affect the melanosome grouping. In African Americans with dark skin, melanosomes are large and nonaggregated, whereas in light-skinned African ...

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