Understanding Moles and Nevi: Your Guide to Skin Health
Most human beings have 50 – 100 harmless moles. These are harmless, benign tumors of melanocytes (or pigment producing cells) which first appear in childhood. Benign or harmless moles are smaller than a pencil eraser, show uniform pigment distribution, are raised, and change very slowly.
Moles increase in number throughout teen and early adult years, but NEW moles after age 40 are unusual and may be dangerous, i.e. melanoma precursors. Moles can be removed for cosmetic reasons, if they are irritated by clothing or shaving, or if they have a worrisome appearance or behavior.
Congenital Nevi
Congenital moles (brown or black “birthmarks”) are very common and are always larger than a pencil eraser. Most small congenital nevi (smaller than a quarter) require removal only if they show worrisome changes since the lifetime risk of transformation into melanoma is very small.
Dysplastic Nevi
The most common abnormal mole is the dysplastic nevus (DN). Most DN exhibit the “ABCDEs” and more than 50% of adults develop these harmless nevi. It is normal to develop DN throughout life. Since a TINY percent of DN patients develop a malignant melanoma, we consider these moles to be “atypical”. The DN patients at greatest risk for developing melanoma have numerous large (eg. bigger than a dime) moles which are changing. For such patients mole mapping (photographs plus measurement) may be recommended. Multiple DN in family members also increases the lifetime risk for developing a melanoma. 25% of new melanomas in DN patients develop in a pre-existent mole while 75% develop in normal skin.
In general we recommend monthly self exam of all DN, preferably in comparison with mole map photos to detect new DN or change in pre-existent DN. We recommend an annual comprehensive dermatology exam for patients with multiple large DN. We biopsy or completely excise DN which are new or changing and have a worrisome appearance.
Seborrheic Keratosis
Patients often consult their dermatologist regarding changing brown growths. The majority of these lesions are seborrheic keratosis (SKs) which are harmless pigmented (light tan, brown, or even black) warty growths which may exhibit the “ABCDEs” of melanoma. They are not caused by sun damage and have no chance to become cancer. An experienced dermatologist can easily make an accurate visual diagnosis (i.e. no biopsy needed) of these benign growths. SKs are hereditary and increase in number and size with advancing age. Removal of SKs is “medically necessary” if they are irritated or symptomatic, although some patients desire removal for cosmetic concerns. Cryotherapy or freezing is the most popular way to destroy these growths, but very thick lesions are most reliably removed by a minor surgical procedure.
Lentigo
One of the most common pigmented lesions on the face, hands, and arms is the lentigo, aka “age spot” or “liver spot”. “Liver spot” refers only to the brown color. Lentigos have no relationship to the liver or liver disease. These are flat, brown lesions which are age-related and caused by sun exposure. They have no potential to become malignant, but occasionally a lentigo maligna (LM) or melanoma is situ can be mistaken for a harmless lentigo. LM is a slow growing lesion which usually has shades of black and brown. Lentigos can be removed for cosmetic reasons by freezing (cryotherapy) or with our Sciton Laser.
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