Atypical nevi (AN) are melanocytic nevi that may exhibit ABCD features similar to those of melanoma, and patients with AN have an increased risk of developing melanoma. Since their first description over 30 years ago, confusion persists about the definition, as well as the clinical and surgical management, of AN. Patients with AN account for a significant percentage of patients seen in general dermatology practices and specialized pigmented lesion clinics, as well as in dermatologic surgical clinics for excision. It is, therefore, imperative that all general and procedural dermatologists understand the complexities of this diagnosis and the challenges of care for these patients. This chapter will review the diagnosis, clinical evaluation, approach for management and skin biopsies, and future directions in the care of patients with AN, including advanced imaging technologies.
In 1978, Wallace H. Clark and colleagues first reported the AN (termed “B-K” nevus by Clark) as a clinicopathologic entity and described particular nevi on individuals at risk for melanoma.1 Several names are used in the literature to refer to such nevi, including AN, dysplastic nevus (DN), and Clark’s nevus. In 1992, the US National Institutes of Health Consensus Conference recommended that AN refer to clinically atypical appearing nevi, while “nevus with architectural disorder” be used for pathologically evaluated nevi with dysplasia. To date, some clinicians use the terms AN and DN interchangeably. For the purpose of this chapter, we will use the term AN for clinically AN, and DN for lesions that have been biopsied with pathologically confirmed dysplasia.
Several definitions and criteria for the Familial Atypical Mole and Melanoma (FAMM) syndrome have been proposed, including one by the aforementioned 1992 conference that defined it by (1) occurrence of melanoma in one or more first- or second-degree relatives, (2) large numbers of moles (often greater than 50), some of which are atypical and often variable in size, and (3) moles that demonstrate certain distinct histologic features of dysplasia defined by the consensus conference. In addition, others have proposed FAMM syndrome as the presence of two or more family members with AN and at least one family member with melanoma.2 The atypical mole syndrome has also been described as the presence of 503 to 1004 or more melanocytic nevi including one or more 8 mm or larger in greatest diameter and one or more with clinically atypical (ABCD) features. In 1980, the term dysplastic nevus syndrome (DNS) was termed to describe the association of sporadic DN with nonfamilial melanoma.5
Clinically, AN have been reported in up to 17% of the Caucasian population.6 Histopathologically, DN are reported at a prevalence of approximately 10%.7,8 AN are reported at a much higher frequency ranging from 34% to 59% among patients with a history of melanoma.9–12 The prevalence of AN is positively associated with fair-skinned ...