Moles in and of themselves are harmless; they're simply a pigmented lesion called "melanocytic nevi" or "pigmented nevi." They can be flat or raised, depending on where the pigmented cells gather in the layers of your skin. The danger is when previously flat moles become raised or raised moles change shape or grow larger. Possible causes include melanoma, a dangerous form of skin cancer, notes the New Zealand Dermatological Society.
Moles can be as small as a pencil tip or as large as a quarter, ranging in color from light pink to brown to black. Some people are born with them, while other moles appear during infancy.
The New Zealand Dermatological Society classifies flat moles as junctional nevi, formed where the outer and inner layers of skin meet. Raised moles, called dermal nevi or compound nevi, form through a cluster of cells in the dermis and cause a raised bump in the skin.
According to the American Academy of Dermatology, light-skinned people have an average of 10 to 40 moles.
Types of Moles
If you were born with your moles, they're called "congenital nevi." The American Academy of Dermatology reports that 1 in 100 babies are born with moles. Large congenital moles that are bigger than 20 centimeters in diameter carry a greater risk for skin cancer.
So-called "atypical moles" develop after birth and can be a mixture of red, pink and brown colors. These are also skin cancer risks. "Acquired moles" also develop after birth but are more regular in color and generally aren't cause for alarm, states the American Academy of Dermatology website.
Moles that Change Color or Texture
If you notice a mole that changes its color, shape or texture, see a dermatologist as soon as possible.
Moles are caused by extra melanocytes, the pigment cells responsible for color. A form of skin cancer called malignant melanoma can form in or near these melanocytes. When the cancerous cells begin expanding, the mole can change shape or color.
Skin cancer isn't the only possibility; however, your mole might be changing temporarily because it's irritated by contact with a razor blade, chemicals in a lotion or sunscreen, or scratchy clothing.
Your doctor may need to remove all or part of the mole to determine whether it's cancerous. Even if a visual exam confirms nothing is wrong, you can have a mole removed for cosmetic reasons. Doctors can perform a shave excision to cut out small moles or excisional surgery to remove larger moles along with some of the surrounding skin. The latter option is used to remove cancerous moles and in most cases, the moles never reappear, according to the Mayo Clinic.
The American Academy of Dermatology recommends performing self-exams to evaluate the condition of your moles. Don't worry if some of your moles look different than others. Just evaluate each mole based on how it looks now versus the last time you checked. Look for the ABCDs: asymmetry, a changing border, changing colors, and diameter. If you see significant changes in one or more features, consult a dermatologist for a skin cancer screening.