Moles (Nevi)
Nevi (plural of nevus) is the medical term for a mole, birthmark, or beauty mark. Moles are common benign skin lesions made of pigment-producing cells known as melanocytes. Melanocytes exist throughout the skin to provide melanin to skin cells. However, in moles, these melanocytes cluster into groups rather than be evenly spread out in the skin. They can appear flat, slightly raised or round, and range in color from brown, black, tan, red, pink, blue, and even colorless.
Acquired nevi describe nevi that develop after birth. Most adults have 10-40 common moles, and they continue to develop moles until about age 40. Moles may fade with time as well. People with fair skin tend to have more moles than people of color. People with 10 or more moles are at 12x the risk for developing melanoma, the most serious type of skin cancer. Moles present at birth are known as congenital nevi.
What is a common mole?
A common mole is a spot on the skin that develops when melanocytes cluster together. It is usually round or oval, flat or raised, of a single color including solid pink, brown or black, with a well-defined border, and smaller than 5mm or a 1/4 inch. Common moles can be found anywhere on the body, including underneath fingernails and between fingers and toes. A common mole has the potential to become a melanoma.
What causes a mole?
A mole is a proliferation of melanocytes that can occur before birth (congenital) or afterward (acquired). Many moles that form during the first few decades of life are thought to be due to sun damage. However, the development of moles has a genetic component as well and the tendency to form moles can be inherited. Sun exposure, immune diseases, and some drug treatments can influence the development of new nevi.
