What is a mole?

Moles (nevi is the medical term) are growths on the skin that range in color from the natural skin tone to brown or black. Moles can appear anywhere on the skin or mucous membranes, alone or in groups.

Most moles appear in early childhood and during the first 20 years of life. It is normal for a person to have between 10 to 40 moles by adulthood. Some moles may not appear until later in life.

The life cycle of an average mole is about 50 years. As the years pass, moles usually change slowly, becoming raised and lighter in color. Often, hairs develop on the mole. Some moles will not change at all and some will slowly disappear over time.

What are the different types of moles?

Congenital Nevi: These are moles that appear at birth. Congenital nevi occur in about 1 in 100 people. These moles may be more likely to develop into melanoma than moles that appear after birth. If the mole is more than eight inches in diameter, it has a greater risk of becoming cancerous.

Dysplastic Nevi: These moles are larger than a pencil eraser and irregularly shaped. Dysplastic nevi tend to have uneven color with dark brown centers and lighter, uneven edges. These moles tend to be hereditary (inherited), and people who have them may have more than 100 moles. People with dysplastic nevi have a greater chance of developing malignant (cancerous) melanoma. Any changes in the mole should be checked by a dermatologist to detect skin cancer.

What causes a mole?

Moles occur when cells in the skin grow in a cluster instead of being spread throughout the skin. These cells are called melanocytes, and they make the pigment that gives skin its natural color. Moles may get darker after sun exposure, during pregnancy, and during puberty in the teen years.