Nevus

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Nevus
Classification and external resources
1D-I-k ouC8.jpg
A nevus on a leg
ICD-10I78.1
ICD-9448.1, 216.0-216.9
MeSHD009506
 
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Nevus
Classification and external resources
1D-I-k ouC8.jpg
A nevus on a leg
ICD-10I78.1
ICD-9448.1, 216.0-216.9
MeSHD009506

Nevus (or naevus, plural nevi or naevi, from nævus, Latin for "birthmark") is the medical term for sharply circumscribed[1] and chronic lesions of the skin or mucosa. These lesions are commonly named birthmarks or beauty marks. Nevi are benign by definition. However, 50% of malignant melanomas (a skin cancer) arise from pre-existing nevi.[2] Using the term nevus and nevi loosely, most physicians and dermatologists are actually referring to a variant of nevus called the "melanocytic nevus", which are composed of melanocytes. Histologically, melanocytic nevi are differentiated from lentigines (also a type of benign pigmented macule) by the presence of nests of melanocytes, which lentigines (plural form of lentigo) lack.

Classification[edit]

Epidermal nevi are derived from keratinocytes or derivatives of keratinocytes. Connective tissue nevi are derived from connective tissue cells like adipocytes and fibroblasts. Vascular nevi are derived from structures of the blood vessels. See birthmark for a more complete discussion

Melanocytic nevus[edit]

Epidermal nevus[edit]

Connective tissue nevus[edit]

Vascular nevus[edit]

Diagnosis of nevi[edit]

A modern polarized dermatoscope

Clinical diagnosis of a melanocytic nevus from other nevi can be made with the naked eye using the ABCD guideline, or using dermatoscopy. The main concern is distinguishing between a benign nevus, a dysplastic nevus, and a melanoma. Other skin tumors can resemble a melanocytic nevus clinically, such as a seborrheic keratosis, pigmented basal cell cancer, hemangiomas, and sebaceous hyperplasia. A skin biopsy is required when clinical diagnosis is inadequate or when malignancy is suspected.

Normal evolution or maturation of melanocytic nevi[edit]

All melanocytic nevi will change with time - both congenital and acquired nevi. The "normal" maturation is evident as elevation of the lesion from a flat macule to a raised papule. The color change occurs as the melanocytes clump and migrate from the surface of the skin (epidermis) down deep into the dermis. The color will change from even brown, to speckled brown, and then losing the color and becomes flesh colored or pink. During the evolution, uneven migration can make the nevi look like melanomas, and dermatoscopy can help in differentiation between the benign and malignant lesions.[3]

See also[edit]

References[edit]

  1. ^ "nevus" at Dorland's Medical Dictionary
  2. ^ Sam, Amir H.; James T.H. Teo (2010). Rapid Medicine. Wiley-Blackwell. ISBN 1405183233. 
  3. ^ [1][dead link]

External links[edit]