Birth marks are pigment spots or areas, often raised above the skin surface. The most common birthmark is the naevus, or large port-wine stain, which is a mass of dilated blood-vessels often located on the face. Small naevus of a reddish or bluish colour are more common elsewhere on the body. Naevus which are darker and hairy are often called moles.
There are two categories of vascular birthmarks. These are hemangiomas, which are the most common tumour of infancy, and vascular malformations. These two categories, while related, require different treatment. Hemangiomas are benign and will regress but vascular malformations will continue to grow.