Naevus Health Dictionary

A type of skin blemish of which there are 2 main groups: pigmented naevi are caused by abnormality or overactivity of melanocytes (skin cells that produce the pigment melanin); vascular naevi are caused by an abnormal collection of blood vessels.

The most common types of pigmented naevi are freckles, lentigos, and café au lait spots: flat brown areas that may occur where the skin is exposed to the sun. Another common type is a mole, sometimes called a melanocytic naevus. In rare cases, moles become cancerous (see melanoma, malignant). Juvenile melanomas (see melanoma, juvenile) are red-brown naevi that occur in childhood. Blue naevi are common in young girls. Most black and Asian infants are born with blue-black spots on their lower backs (see Mongolian blue spot).

Port-wine stains and strawberry marks (see haemangioma and spider naevi) are examples of vascular naevi.

Most naevi are harmless. However, if a naevus suddenly appears, grows, bleeds, or changes colour, medical advice should be sought immediately to exclude the possibility of skin cancer.

A congenitally determined tissue abnormality. In the SKIN, naevi of blood vessels are best known, but a MOLE is a MELANOCYTE naevus, and warty streaked and linear naevi of the epidermis occasionally occur. There are several patterns of vascular naevi:

Naevus simplex Also known as ‘salmon patch’. About one-third of white children are born with macular pink areas of ERYTHEMA on the nape, brow or eyelids which usually disappear after a few months, but patches on the nape may persist.

Naevus ?ammeus Also known as ‘portwine stain’ and present at birth. It is unilateral, usually on the face, and may be extensive. It tends to darken with age and is permanent. Laser treatment is e?ective.

Strawberry naevus (cavernous haemangioma) is usually not present at birth but appears within a few weeks and grows rapidly, reaching a peak in size after 6–12 months, when the lobulated red nodule may resemble a ripe strawberry. Untreated, the naevus disappears spontaneously over several years. It may occur anywhere and may be very troublesome when occurring around an eye or on the ‘nappy’ area. If possible it should be left alone, but where it is causing problems other than simply cosmetic ones it is best treated by an expert. This may involve medical treatment with steroids or interferon or laser therapy.

Spider naevus is due to a dilated ARTERIOLE causing a minute red papule in the skin, the small branching vessels resembling spider legs. A few spider naevi are common in young people, but multiple naevi are common in pregnancy and may also be a warning sign of chronic liver disease.

n. (pl. naevi) a birthmark: a clearly defined malformation of the skin, present at birth. There are many different types of naevi. Some, including the strawberry naevus and port-wine stain, are composed of small blood vessels (see haemangioma). The strawberry naevus (or strawberry mark) is a raised red lump usually appearing on the face and growing rapidly in the first month of life. These birthmarks slowly resolve and spontaneously disappear between the ages of five and ten. The port-wine stain (or capillary naevus) is a permanent purplish discoloration that may occur anywhere but usually appears on the upper half of the body. Laser treatment can reduce the discoloration. Occasionally a port-wine stain may be associated with a malformation of blood vessels over the brain, for example in the Sturge-Weber syndrome (see angioma).

It is not uncommon for a pale or white halo to develop around an ordinary pigmented naevus, especially on the trunk, forming a halo naevus. The pigmented naevus disappears over the course of a few months; this is followed by resolution of the pale area. A blue naevus is a small blue-grey papule appearing at birth or later in life, mainly on the extremities. Progression to malignant melanoma is very rare. A naevus of Ota is a blue-grey pigmented area on the cheek, eyelid, or forehead with similar pigmentation of the sclera of an eye. It is associated with melanomas of the uvea, orbit, and brain as well as with glaucoma of the affected eye. See also mole2.