(Dysplastic Nevus; Atypical Nevus)
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.
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
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.
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:
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.
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.