Atypical Moles

(Dysplastic Nevus; Atypical Nevus)

By Denise M. Aaron, MD, New, Dartmouth-Hitchcock Medical Center

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Benign Skin Tumors, Growths, and Vascular Lesions
Atypical Moles
Capillary Malformations
Cutaneous Cysts
Dermatofibromas
Infantile Hemangiomas
Keloids
Lipomas
Lymphatic Malformations
Moles
Nevus Araneus
Pyogenic Granulomas
Seborrheic Keratoses
Skin Tags
Vascular Lesions of the Skin

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 (AM) are nevi with a slightly different clinical and histologic appearance (disordered architecture and atypia of melanocytes). Most melanomas arise de novo. Risk factors for melanoma include increased number of AM and increased exposure to ultraviolet radiation and sun. Some patients have only one or a few AM; others have many.

The propensity to develop AM may be inherited (autosomal dominant) or sporadic without apparent familial association. Familial atypical mole–melanoma syndrome refers to the presence of multiple AM and melanoma in ≥ 2 1st-degree relatives. These patients are at markedly increased risk (25 times) of melanoma.

Diagnosis

Clinical evaluation
Sometimes biopsy
Regular physical examinations

AM 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 yr of age or a changing mole

Although clinical findings can sometimes establish a diagnosis of AM (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 often 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 AM 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 do imaging of the skin using a hand-held instrument (dermoscopy) to see structures not visible to the naked eye. Dermoscopy can reveal certain high-risk characteristics.

Treatment

Removal by excision or shaving when desired
Excision of high-risk lesions

If desired, AM can be removed by excision or shaving.

Prophylactic removal of all AM 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

Sun protection
Regular self-examination
Full-body photography
Sometimes surveillance of family members

Patients with AM should avoid excessive sun exposure and use sunscreens. Patients who are vigilant about sun protection should be counseled to take sufficient supplemental vitamin D. Also, they should be taught self-examination to detect changes in existing moles and to recognize features of melanomas. Full-body photography may help detect new nevi and monitor existing nevi for changes. Regular follow-up examinations are recommended.

If patients have a history of melanoma (whether developing from AM or de novo) or other skin cancers, 1st-degree relatives should be examined. Patients who are from melanoma-prone families (ie, ≥ 2 1st-degree relatives with cutaneous melanomas) have a high lifetime risk of developing melanomas. The entire skin (including the scalp) 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 AM, increased sun exposure, or familial atypical mole–melanoma syndrome.
Because clinical differentiation from melanoma can be difficult, biopsy the worst-appearing AMs.
Closely follow patients with AM, particularly those at higher risk of melanoma, and do full-body photography.
Recommend sun protection (with supplemental vitamin D) and self-examination for high-risk changes.
Do full-body examinations of all 1st-degree relatives of patients who have melanoma.