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Atypical nevus in Child
See also in: Hair and Scalp
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Atypical nevus in Child

See also in: Hair and Scalp
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Contributors: William M. Lin MD, Susan Burgin MD, Craig N. Burkhart MD, Dean Morrell MD, Nancy Esterly MD
Other Resources UpToDate PubMed

Synopsis

An atypical nevus is a benign melanocytic lesion that appears clinically atypical with asymmetry, large size, irregular or ill-defined borders, and/or varied coloration. A dysplastic nevus (also referred to as Clark nevus) is generally regarded as a histopathologic term, where a melanocytic proliferation shows architectural disorder and cytologic atypia and shares some features of melanoma. Dysplastic nevi usually appear clinically atypical and atypical nevi may be dysplastic; however, the clinical and histopathologic terms do not always completely correlate.

There is controversy around the term dysplastic nevus including a lack of consensus on how it is defined and what it represents biologically. Originally described in melanoma-prone families, dysplastic nevi were part of a clinical phenotype. Patients characteristically had numerous nevi, which often appeared clinically atypical; on biopsy (as initially described by Dr. Wallace Clark), four main histologic features were observed: 1) atypical melanocytic hyperplasia, 2) melanocytes with cytologic features characteristic of malignant melanocytes, 3) mesenchymal changes in the papillary dermis, and 4) lymphocytic infiltrate. Since then, dysplastic nevi have been recognized to occur spontaneously, and different variations of the above diagnostic criteria (including grading of cytologic atypia as mild, moderate, or severe) have been proposed without a clear diagnostic consensus.

Dysplastic nevi usually begin to appear in childhood through early adult years and have an estimated prevalence ranging from 2%-10%. The incidence of histologically proven dysplastic nevi is estimated at 2.2% in children aged younger than 12 years and 1.3% in adolescents. More atypical nevi usually begin to appear around puberty. They are thought to have a genetic component and are more common in phototype I-III individuals. While less prevalent than common nevi, dysplastic nevi are believed to correlate with the overall number of melanocytic lesions in an individual and are thought to confer a 4- to 15-fold increased risk of melanoma.

While there is an increased relative risk of melanoma in individuals with multiple dysplastic nevi and dysplastic nevi can share clinical and histologic features with melanoma, current evidence does not support a dysplastic nevus as a definite premalignant lesion. Studies have shown that most melanomas appear to arise de novo without an associated nevus, and even when an associated nevus is present in histologic contiguity with melanoma, it is more frequently a common nevus than a dysplastic nevus.

Codes

ICD10CM:
D23.9 – Other benign neoplasm of skin, unspecified

SNOMEDCT:
254818000 – Atypical nevus of skin

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Last Updated: 07/20/2016
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Atypical nevus in Child
See also in: Hair and Scalp
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Atypical nevus : Hyperpigmented macule, Irregular configuration, Multicolored plaque, Pigmented papule, Pigmented plaque
Clinical image of Atypical nevus
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