Ask the Expert: What Is the Difference Between a Precancer and an Atypical Mole?

Q: What is the difference between a precancer and an atypical mole? Why are atypical moles sometimes removed?

A precancerous skin lesion is a growth that can carry the same mutations present in fully manifested skin cancers, but to a lesser extent. The most common type of skin precancer is called actinic keratosis (AK). AKs carry the same mutations as nonmelanoma skin cancers, especially squamous cell carcinomas (SCCs), and some experts even consider them early SCCs, but in general AKs have fewer, less developed mutations than full-fledged SCCs. Some AKs, if left untreated, will eventually progress into nonmelanoma skin cancers, most often SCCs. The majority of SCCs begin as AKs.

An atypical mole, also sometimes called a dysplastic nevus, is a benign but unusual-looking mole that can look a lot like a melanoma. It’s important to be aware of these moles, because they can turn into melanomas. Atypical moles carry some of the same mutations found in melanomas, but significantly fewer. When they keep accumulating mutations, above all caused by sun exposure, they can transform into melanomas.

About the Expert:

Maritza I. Perez, MD, is founder and director of Advanced Aesthetics in New Canaan, Connecticut, a clinical professor of dermatology at the Icahn School of Medicine at Mount Sinai and an attending physician in the Mount Sinai Health System hospitals in New York City. She is a senior vice president of The Skin Cancer Foundation.