Moles, which are also present at birth, are smaller and more regular in shape. Freckles and liver spots appear after birth in response to sunlight exposure and age. All these types of lesions are due to the overproduction of pigment by pigment cells, or by too high a concentration of pigment cells. Tattoos are produced by introducing pigmented particles into the skin, usually by piercing the skin with a needle coated with the pigment. The needle passes through the outermost layer of skin and deposits the pigment into a lower layer of skin or fat.
Tattoos done by amateurs produce tattoos of a single, blue-black color.
Professional tattoos usually have a higher density of pigment and can include a variety of colors. Vascular lesions are caused by the unregulated growth of blood vessels in an area that follows no discernible pattern of distribution. The vessels are larger than normal and can be thought of as loose, baggy vessels filled with blood. The reason for this unregulated blood vessel growth is not known. Pigmented lesions, aside from tattoos, result from a similar lack of regulation in the production of pigment or pigment cells.