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Nevus



Nevus
Classification & external resources
Photograph of a nevus on an arm
ICD-9 216.0-216.9
MeSH D009506

Nevus (or naevus, plural nevi, from nævus, latin for birthmark) is the medical term for sharply-circumscribed and chronic lesions of the skin. These lesions are commonly named birthmarks and moles. By definition, nevi are benign.

Additional recommended knowledge

Classification

  • Melanocytic nevus (nevomelanocytic nevus, nevocellular nevus): benign proliferation of melanocytes, the skin cells that make the brown pigment melanin. Hence, most nevi are brown to black. They are very common; almost all adults have at least one, usually more. They may be congenital or acquired, usually at puberty. The melanocytic nevi are classified as such:
    • Junctional nevus: the nevus cells are located along the junction of the epithelium and the underlying dermis. A junctional nevus is flat and brown to black.
    • Compound nevus: a mixture of junctional and intradermal proliferation. Compound nevi are slightly raised and brown to black.
    • Intradermal nevus: the nevus cells are located in the dermis only. Intradermal nevi are raised; most are flesh-colored (not pigmented).
    • Dysplastic nevus (nevus of Clark): usually a compound nevus with cellular and architectural dysplasia. They tend to be larger (more than 6 mm), with irregular borders and irregular coloration. Hence, they ressemble melanoma, appear worrisome and are often removed to clarify the diagnosis. Dysplastic nevi do not transform into melanoma but are a marker of risk when they are numerous (atypical mole syndrome).
    • Blue nevus: the nevus cells are very deep in the dermis.
    • Spitz nevus: a distinct variant of intradermal nevus, usually in a child. They are raised and reddish (non-pigmented). A pigmented variant, called the nevus of Reed, typically appears on the leg of young women.
    • Giant Hairy Nevus: these large, pigmented, often hairy congenital nevi can be a source of much psychological and social suffering. They are also important because melanoma may occasionally (10 to 15%) appear in them.
    • Intramucosal nevus: junctional nevus of the mucosa of the mouth or genital areas. In the mouth, they are found most frequently on the hard palate.
    • Nevus of Ito and Nevus of Ota: congenital, flat brownish lesions on the face or shoulder.
    • Mongolian spot: congenital large, deep, bluish discoloration on the back of Asian babies.
  • Epidermal lesions:
    • Epidermal nevus: congenital, flesh-colored, raised or warty, often linear lesion, usually on the upper half of the body.
    • Nevus sebaceus: variant of epidermal nevus on the scalp presenting as a hairless, fleshy or yellowish area.
  • Connective tissue lesions:
    • Connective tissue nevus: fleshy, deep nodules. Rare.
  • Vascular lesions. See birthmark for a more complete discussion:
    • Hemangioma (strawberry mark or nevus).
    • Nevus flammeus (port-wine stain).
    • Spider angioma (nevus araneus).
    • Blue Rubber Bleb Nevus Syndrome: dilatation of veins anywhere in the body (both skin and internal organs), usually lethal from internal hemorrhage. It is a very rare genetic disorder.


 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Nevus". A list of authors is available in Wikipedia.
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