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Thus nevus cells show limited proliferation and cells

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Unformatted text preview: tes. Thus, nevus cells show limited proliferation and cells in common acquired nevi have no apparent chromosomal aberrations. Nevi can develop not just through a stimulatory event, but also through loss of control of keratinocytes over melanocytes. Progression from the melanocyte or common acquired nevus cell to a dysplastic nevus or RGP melanoma most likely involves the onset of genetic aberrations. The cells show cytologic atypia, they can separate from the basement membrane without undergoing apoptosis, and the entire lesion shows architectural atypia. Cells from RGP lesions have biologic properties in vitro that are intermediate between benign and malignant. VGP primary melanomas are characterized as expanding nodules that invade deep into the dermis. VGP primary melanomas are 6 highly aneuploid. Biologically, the cells are relatively plastic, some also acquire metastatic competence. Metastatic cells show a high level of genetic instability, and phenotypic plasticity, depending on the environment and any selective pressure placed on the cells (5, 6). Metastatic cells are highly motile and independent of growth factors, and have acquired the capacity to invade other tissues and organs Melanoma risk factors As in most types of cancers, there are two sets of factors that present significant risk for melanoma in humans: host characteristics and environmental factors. Epidemiologic studies have identified host factors important for risk of melanoma. These include family history of melanoma, alterations in melanoma susceptibility genes, number and type of nevi, skin type and pigmentation (7). Melanoma is more common in individuals with fair skin, blue or green eyes, red or blond hair, many freckles and in individuals who react to sunlight by burning rather than tanning. UV radiation is the most important environmental factor in the development of melanoma. Intermittent repeated exposures to sunlight from childhood are epidemiologically shown to be a major cause of melanom...
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