Bathing trunk nevus

Alternative names:

congenital giant pigmented nevus; giant hairy nevus

Definition:

A disfiguring, darkly pigmented, often hairy patch of skin (nevus) that is present at birth and may cover an extremely large area of the body, sometimes covering most of the trunk and the upper arms and thighs.

Causes, incidence, and risk factors:

Bathing trunk nevi are thought to be congenital, but in some families the frequent appearance of these lesions suggests a hereditary component.

The surface texture may vary from smooth to warty, and the color varies from brown to bluish black. Bathing trunk nevi may cause psychological (emotional) problems because of their cosmetic appearance.

More importantly, the nevus has a high risk of developing into malignant melanoma (a type of skin cancer). The risk is thought to be between 10% and 15%, although this number varies in different medical studies.