An atypical mole, medically known as a dysplastic nevus, is a common skin growth that differs in appearance from an ordinary mole. While these lesions are not skin cancer, they possess features that place them on a spectrum between a common mole and melanoma, the most serious form of skin cancer. Understanding the nature and appearance of these moles is the first step toward appropriate skin health management.
Defining Dysplastic Nevi
The formal medical name for an atypical mole is a dysplastic nevus. These are benign proliferations of pigment-producing cells (melanocytes) that exhibit architectural disorder and cellular atypia when viewed under a microscope. This means the cells are growing in an abnormal, disorganized pattern and may have slightly irregular features, but they are not yet cancerous.
Common moles (nevi) are typically small, uniform, and symmetrical clusters of melanocytes that form during childhood. Dysplastic nevi often appear later, around puberty or early adulthood, and frequently occur on the trunk and extremities, though they can develop anywhere on the body. About one in ten people in the United States has at least one dysplastic nevus. While the presence of a few atypical moles is common, having a large number—typically 50 or more—is a specific risk factor that warrants increased vigilance.
Key Visual Characteristics of Atypical Moles
Atypical moles are clinically distinguishable from common moles because they often display several irregular features, summarized using the well-known ABCDE criteria. This mnemonic helps identify lesions suspicious for an atypical mole or developing melanoma. A stands for asymmetry, where one half of the mole does not mirror the other half.
B for border describes edges that are scalloped, ragged, or poorly defined, instead of the smooth, round outline of a common mole. C represents color variation, meaning the mole contains multiple shades of color, which may include light tan, dark brown, black, or even shades of pink, red, or blue. The D in the criteria stands for diameter, with atypical moles often measuring larger than six millimeters, roughly the size of a pencil eraser.
Finally, the E is for evolution, meaning any change in the mole’s size, shape, color, or elevation over time is a warning sign. Atypical moles may also look different from the rest of the moles on an individual’s body, a concept known as the “ugly duckling” sign. The presence of multiple characteristics increases clinical suspicion and necessitates a professional evaluation.
Atypical Moles and Melanoma Risk
The primary concern regarding atypical moles stems from their association with an increased lifetime risk of developing melanoma. While the majority of dysplastic nevi remain benign, they are considered markers for heightened susceptibility. Experts estimate that approximately one in four cases of melanoma may arise from a pre-existing atypical mole, though most melanomas develop spontaneously on previously clear skin.
The risk level is directly related to the number of atypical moles an individual possesses. People with five or more dysplastic nevi, for instance, have a risk of melanoma about ten times greater than the general population. This risk dramatically increases for individuals diagnosed with Familial Atypical Multiple Mole Melanoma (FAMMM) syndrome, sometimes called Atypical Mole Syndrome. This inherited condition is characterized by a large number of atypical moles coupled with a family history of melanoma.
In those with FAMMM syndrome, a gene mutation can lead to a significantly elevated risk of melanoma development, sometimes reported to be 25 times higher than the average person. While a single atypical mole presents a small risk, the overall context of an individual’s skin—including the total count and family history—determines the true level of concern.
Clinical Management and Monitoring
Because of the potential link to melanoma, the management of atypical moles focuses heavily on careful monitoring and early detection. The first step for anyone with an unusual-looking mole is to consult a dermatologist for a professional evaluation. The dermatologist may perform a full-body skin examination, which often includes a process called dermoscopy to examine the mole’s structure under magnification.
Patients with multiple atypical moles or a high-risk profile, such as those with FAMMM syndrome, are often advised to undergo total-body photography, or “skin mapping,” to establish a baseline record. This photographic record helps track any changes in existing moles or the appearance of new lesions over time. Regular professional skin checks are recommended, with the frequency ranging from every three to twelve months, depending on the patient’s specific risk factors.
Self-examination is also an important part of the monitoring process; patients are taught to check their skin monthly for any signs of change. If a mole is highly suspicious for melanoma, a biopsy or surgical excision is performed to remove the entire lesion for microscopic analysis. For moles confirmed as dysplastic but not cancerous, the decision to remove them is guided by the degree of atypia and whether the mole was completely excised during the initial biopsy.