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Atypical Moles

(Dysplastic Nevus; Atypical Nevus)

By Denise M. Aaron, MD

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Patient Education

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). Patients with AM are at increased risk of melanoma. It is estimated that about 20% of AM will progress to melanoma. 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.

Symptoms and Signs

AM 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

  • 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.

Resources In This Article

* This is the Professional Version. *