Atypical moles are benign melanocytic nevi with irregular and ill-defined borders, variegated colors usually of brown and tan tones, and macular or papular components. Patients with atypical moles have an increased risk of melanoma. Management is by close clinical monitoring and biopsy of highly atypical or changed lesions. Patients should reduce sun exposure and conduct regular self-examinations for new moles or changes in existing ones.
Atypical moles are nevi with a slightly different clinical and histologic appearance (disordered architecture and atypia of melanocytes). Some patients have only one or a few atypical moles; others have many. Although most melanomas arise de novo, some develop from atypical moles (1). Risk factors for melanoma include increased number of atypical moles and increased exposure to ultraviolet radiation and sun.
This image shows an atypical nevus, with the characteristic irregular border and variable coloration.
Image courtesy of Marie Schreiner, PA-C.
This image shows atypical nevi, with characteristic irregular borders and variable coloration.
Image courtesy of Marie Schreiner, PA-C.
This photo shows a rounded mole with irregular borders.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
This image shows an atypical nevus, with the characteristic irregular border and variable coloration.
Image courtesy of Marie Schreiner, PA-C.
This image shows atypical nevi, with characteristic irregular borders and variable coloration.
Image courtesy of Marie Schreiner, PA-C.
This photo shows a rounded mole with irregular borders.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
The propensity to develop atypical moles may be inherited (autosomal dominant) or sporadic without apparent familial association. Familial atypical multiple mole–melanoma syndrome refers to the presence of multiple atypical moles and melanoma in ≥ 2 first-degree relatives. These patients are at markedly increased risk of melanoma (2).
General references
1. Friedman RJ, Farber MJ, Warycha MA, et al: The "dysplastic" nevus. Clin Dermatol 27(1):103-115, 2009. doi: 10.1016/j.clindermatol.2008.09.008
2. Soura E, Eliades PJ, Shannon K, et al: Hereditary melanoma: Update on syndromes and management: Genetics of familial atypical multiple mole melanoma syndrome. J Am Acad Dermatol. 74(3):395-407, 2016; quiz 408-10. doi: 10.1016/j.jaad.2015.08.038
Symptoms and Signs of Atypical Moles
Atypical moles are often larger than other nevi (> 6 mm diameter) and primarily round (unlike many melanomas) but with indistinct borders and mild asymmetry. In contrast, melanomas have greater irregularity of color and may have areas that are red, blue, whitish, or depigmented with a scarred appearance.
Diagnosis of Atypical Moles
Clinical evaluation
Dermatoscopic evaluation
Biopsy
Regular physical examinations
Atypical moles must be differentiated from melanoma. Features that suggest melanoma, known as the ABCDEs of melanoma, are
A: Asymmetry—asymmetric appearance
B: Borders—irregular borders (ie, not round or oval)
C: Color—color variation within the mole, unusual colors, or a color significantly different or darker than the patient's other moles
D: Diameter—> 6 mm
E: Evolution—a new mole in a patient > 30 years of age or a changing mole
Although clinical findings can sometimes establish a diagnosis of atypical moles (see table Characteristics of Atypical vs Typical Moles), visual differentiation between atypical nevi and melanoma can be difficult; biopsy of the worst-appearing lesions should be done to establish the diagnosis and to determine the degree of atypia. Biopsy should aim to include the complete depth and breadth of the lesion; excisional biopsy is ideal.
Characteristics of Atypical vs Typical Moles
Criteria | Typical Moles | Atypical Moles |
|---|---|---|
Age of onset | Childhood or adolescence | Continue to appear after adolescence |
Color | Flesh-colored, yellow-brown, or black | Tan to dark brown with a pink background; often resembling a fried egg, with a dark or light target commonly with a flatter rim than center Pigment often blurred at the edges or notched |
Diameter | 1–10 mm (usually < 6 mm) | 5–12 mm |
Shape | Symmetric with regular borders | Can be asymmetric or with irregular borders |
Location | Anywhere on the body | Most common on sun-exposed skin but may occur on covered areas (eg, buttocks, breasts, scalp) |
Number of lesions | ≤ 10 | One to several dozen |
Patients with multiple atypical moles and a personal or family history of melanoma should be examined regularly (eg, yearly for family history of melanoma, more often for personal history of melanoma). Some dermatologists observe pigment patterns of melanocytic lesions using a hand-held instrument known as a dermatoscope. Dermoscopy allows a dermatologist to see structures not visible to the naked eye. Dermoscopy can reveal certain high-risk characteristics suggestive of melanoma (eg, blue-white veil, irregular dots and globules, atypical pigment network, reverse network).
Treatment of Atypical Moles
Removal by excision or shave excision when desired
Complete excision of highly atypical lesions
Prophylactic removal of all atypical moles is not effective in preventing melanoma and is not recommended. However, atypical moles may warrant removal for any of the following conditions:
A patient has a high-risk history (eg, personal or family history of melanoma).
A patient cannot guarantee close follow-up.
The mole has high-risk dermatoscopic findings.
The mole is in a location that makes monitoring the lesion for changes difficult or impossible for the patient.
Prevention of Atypical Moles
Sun protection (ie, sun-protective clothing, sunscreen, sun avoidance during peak times, seeking shade)
Regular self-examination
Full-body photography
Sometimes surveillance of family members
Patients with atypical moles should avoid excessive sun exposure and use sun protection
If patients have a history of melanoma (whether developing from atypical moles or de novo) or other skin cancers, 1st-degree relatives should be examined. Patients who are from melanoma-prone families (ie, ≥ 2 first-degree relatives with cutaneous melanomas) have a high lifetime risk of developing melanomas. The entire skin (including the scalp and genitals) of members of an at-risk family should be examined at least once to determine risk and needed follow-up.
Key Points
Risk of melanoma is higher if patients have increased numbers of atypical moles, increased sun exposure, or familial atypical multiple mole–melanoma syndrome.
Because clinical differentiation from melanoma can be difficult, biopsy the most suspect atypical moles.
Closely follow patients with atypical moles, particularly those at higher risk of melanoma, and do full-body photography.
Do full-body examinations of all 1st-degree relatives of patients who have melanoma.
