Atypical moles (atypical nevi) are nevi that share some clinical features with melanoma, such as size greater than a pencil eraser(5mm), cobblestone texture, asymmetry, notching of the border and variegated (multiple) colors, but differ from melanoma in that they are not cancerous. Although, rarely, atypical moles can become melanoma, the vast majority will not. People with atypical moles, are at a slightly greater risk of developing melanoma (3-20 fold higher risk), depending on the number of atypical nevi they possess. The more atypical nevi present, the greater the risk of developing melanoma.
All patients with a history of atypical nevi should be under dermatological care, and have regular (at least annual) full skin exams. Monthly self skin exams, sun avoidance and sunscreen use are essential, and it would be prudent to have family members checked as well for atypical nevi. Atypical nevi are gradedby the dermatopathologist who examines the tissue after biopsy or excision, and are often labeled “mild, moderate, or severe” based upon their histopathological characteristics.
When a biopsy of a mole reveals an atypical mole or nevus, often it will be necessary to surgically excise any remaining lesion if the initial biopsy margins were involved, but this can be best determined by the degree of atypia. While re-excision may not be necessary for atypical nevi with positive histologic margins showing mild, mild to moderate, or moderate atypia, patients with atypical nevi showing moderate to severe and severe histologic atypia and positive biopsy margins may benefit from re-excision to confirm the diagnosis and exclude melanoma. Ultimately the decision to re-excise an atypical nevus is best discussed with your skin care specialist.