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 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.
If a dermatologist believes a mole needs to be evaluated further or removed entirely, he or she will either remove the entire mole, or first take just a small tissue sample of the mole to examine thin sections of the tissue under a microscope (a biopsy). This is a simple procedure. (If the dermatologist thinks the mole might be cancerous, cutting through the mole will not cause the cancer to spread.) Read more about moles, freckles, and skin tags.
Slideshow: Slideshow: A Visual Guide to Birthmarks