Moles are pigmented spots on the skin. The medical term for mole is nevus (plural, nevi). Most moles are harmless and normal, and remain stable over a lifetime. However, having certain types of moles increases your risk of developing melanoma.

• A change in the size, shape, or color of an existing mole or the appearance of a new mole is often the first sign of melanoma. If you note any of these changes, contact your doctor for a professional skin examination. (See Early Detection for more information.)
• Congenital nevi are moles that are present at birth or become apparent in early infancy. They occur in about 1 to 2% of all newborns. Most congenital nevi are small and pose a low risk of developing into melanomas. Risk increases with nevus size. Giant nevi, which cover major areas of the head or body, pose the greatest risk, with almost half of melanomas developing before the age of 5. ¹
• Dysplastic nevi are also known as atypical moles. They may occur anywhere on the body but are found most frequently on the back and on sun-exposed areas. Dysplastic nevi are generally larger than normal moles and have irregular or indistinct borders. There are often variations of color within the mole, ranging from pink to dark brown. Individuals with dysplastic nevi and no personal or family history of melanoma have a 7 to 27 times greater risk of developing melanoma than the general population. The risk is increased significantly if there is also a personal or family history of melanoma.
• Dysplastic nevus syndrome or atypical mole syndrome is a condition characterized by the presence of 100 or more moles on the upper trunk and limbs, at least one of which is dysplastic. The syndrome may be acquired or inherited. Individuals with acquired DNS (who do not have a family history of melanoma) have an increased risk of developing melanoma. However, individuals with DNS and a family history of melanoma are at the highest risk of developing melanoma, with a lifetime risk that approaches 100% by age 70. ²
• If you have 50 or more small, normal moles, or five or more normal moles of at least 5 millimeters (almost 1/4 inch) in diameter, you are at 3 times the risk of developing melanoma than the general population. This is because melanoma usually arises in existing moles, so having numerous moles increases the risk.

See Moles and Other Lesions for more information about moles.