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. Risk factors for melanoma include increased number of atypical moles and increased exposure to ultraviolet radiation and sun.
The propensity to develop atypical moles may be inherited (autosomal dominant) or sporadic without apparent familial association. Familial atypical 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 (25 times) of melanoma.
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
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 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.
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)
Sometimes surveillance of family members
Patients with atypical moles should avoid excessive sun exposure and use sun protection Prevention The skin may respond to sunlight with chronic (eg, dermatoheliosis [photoaging], actinic keratosis) or acute (eg, photosensitivity, sunburn) changes. The sun emits a wide range of electromagnetic... read more . 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 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.
Risk of melanoma is higher if patients have increased numbers of atypical moles, increased sun exposure, or familial atypical 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.
Recommend sun protection (with supplemental vitamin D) and regular self-examination for high-risk patients.
Do full-body examinations of all 1st-degree relatives of patients who have melanoma.