Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 1997.
What is a blue naevus?
A blue naevus (nevus) is a rather unusual and harmless mole.
The blue naevus is a dark blue colour because the pigment cells (melanocytes) are deeper in the skin than in commoner brown moles and freckles. Characteristically, the view seen with dermoscopy is a uniform steel-blue pattern.
Clinical features of blue naevi
Blue nevi may be found anywhere on the body, but are often found on the scalp, face, hands and feet. They usually appear in older children and teenagers, but may develop at any age. They remain stable.
Most blue naevi are just a few millimetres in diameter and round in shape. They may be flat or elevated. Sometimes they have a dryish surface.
Although most blue naevi are blue in colour, they are sometimes another colour (usually grey, brown or yellowish).
Blue naevi, with dermatoscopic views
How is the diagnosis made?
Blue naevi are usually diagnosed clinically by their typical appearance.
If there is any doubt about the diagnosis, they may be excised for histopathology (biopsy). Spindle-shaped pigment cells (melanocytes) are found in the dermis.
Treatment of blue naevi
No treatment is needed as blue naevi are harmless. However, some people with a blue naevus on an exposed part of the body ask for it to be removed for cosmetic reasons. If the lesion has only recently appeared, your doctor may to prefer to remove it to make sure it is not a dangerous skin cancer, malignant melanoma.
Removal involves a small surgical excision after an injection of local anaesthetic. It takes about twenty minutes, and leaves a small scar.