You should check out all the other literary ones from that challenge:
Birthmarks fall into two categories: pigmented or vascular (I'll deal with those in the future). Birthmarks (both types) are present at birth or develop shortly after birth. Pigmented birthmarks can be brown, tan, black, or bluish/bluish-gray. The cause of pigmented birthmarks is unknown. Most birthmarks are not inherited. There is no known way to prevent birthmarks. People with birthmarks, just like everyone else, should use a good quality sunscreen with a high SPF when outdoors in order to help prevent skin cancer. In most cases, health care professionals can diagnose birthmarks based on the appearance of the skin. Many folk tales and myths exist about the causes of birthmarks, but none of these stories have been proven to explain the true causes of birthmarks. Photo credit
Types of Pigmented Birthmarks
Cafe-au-lait spots are light tan or light brown spots that are usually oval in shape. They usually appear at birth but may develop in the first few years of a child's life. Cafe-au-lait spots may be a normal type of birthmark, but the presence of several cafe-au-lait spots larger than a quarter may occur in neurofibromatosis (a genetic disorder that causes abnormal cell growth of nerve tissues).
Congenital nevi are moles that are present at birth. These birthmarks have a slightly increased risk of becoming skin cancer depending on their size. Larger (covers an area larger than the size of a fist) congenital nevi have a greater risk of developing skin cancer than do smaller congenital nevi. All congenital nevi should be examined by a health care provider and any change in the birthmark should be reported.
Pigmented nevi (moles) are growths on the skin that usually are flesh-colored, brown or black. Moles can appear anywhere on the skin, alone or in groups. Moles occur when cells in the skin grow in a cluster instead of being spread throughout the skin. Moles may darken after exposure to the sun, during the teen years and during pregnancy.
Mongolian spots usually are bluish and appear as bruises. They often appear on the buttocks and/or lower back, but they sometimes also appear on the trunk or arms. The spots are seen most often in people who have darker skin. They usually fade (often completely) by school age without treatment.
Treatment of Pigmented Birthmarks
Pigmented birthmarks are usually left alone, with the exception of moles and, occasionally, café-au-lait spots. Moles, particularly large or giant congenital nevi, often are surgically removed, though larger ones may be more difficult to remove. Café-au-lait spots can be removed with lasers (highly concentrated light energy) but often return. If a mole exhibits potentially cancerous changes, a biopsy may be performed. Large or prominent moles that affect appearance and self-esteem may be covered with special cosmetics.
Since there is an increased risk of skin cancer in congenital nevi, see a doctor if you notice a change in color, size, or texture of a mole or other skin lesion. Also, see a doctor right away if there is any pain, bleeding, itching, inflammation, or ulceration of a congenital mole or other skin lesion.