A teenage boy presents with concern over a mole on his back that his mother says is growing larger and more variable in color. His mother, who is present with him, reports that his father had a melanoma that was caught early and successfully treated. The edges are irregular and the color almost appears to be “leaking” into the surrounding skin. He reports no symptoms related to this lesion. On physical exam, the nevus is 9 mm in diameter with asymmetry, variations in color and an irregular border (Figure 146-1). A full-body skin exam did not demonstrate any other suspicious lesions. Dermoscopy showed an irregular network with multiple asymmetrically placed dots off the network (Figure 146-2). A scoop saucerization was performed with a DermaBlade taking 2-mm margins of clinically normal skin (Figure 146-3). The pathology showed a completely excised compound dysplastic nevus with no signs of malignancy. No further treatment was needed except yearly skin exams to monitor for melanoma.

Dysplastic nevi (DN)/atypical moles are acquired melanocytic lesions of the skin whose clinical and histologic definitions are controversial and still evolving. These lesions have some small potential for malignant transformation and patients with multiple DN have an increased risk for melanoma.¹

The presence of multiple DN is a marker for increased melanoma risk, similar to red hair, and, analogously, cutting off the red hair or cutting out all the DN does not change melanoma risk. The problem with DN is that any one lesion suspicious for melanoma must be biopsied to avoid missing melanoma, not to prevent melanoma from occurring in that nevus in the future.

Atypical nevus, atypical mole, Clark nevus, nevus with architectural disorder, and melanocytic atypia.¹

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  DN are uncommon in children; in a study of Swedish children (N = 524), none had DN.² In another study of pathology reports from nevi removed from patients younger than 18 years, 3 of 199 nevi submitted for histologic analysis met the histologic criteria for DN.³

  
  
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  Two percent to 9 percent of the population has atypical moles (AMs).^4,5 Among patients with melanoma, the rate of DN ranges from 34 to 59 percent.⁴

  
  
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  Individuals with fair skin types are at higher risk of DN.⁴

  
  
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  The sudden eruption of benign and atypical melanocytic nevi has been reported and is associated with blistering skin conditions and a number of disease states, including immunosuppression. Subsets of patients with immunosuppression have increased numbers of nevi on the palms and soles.⁶

  
  
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  The National Institute of Health Consensus Conference on the diagnosis and treatment of early melanoma defined a syndrome of familial atypical mole and melanoma (FAMM). The criteria of FAMM syndrome are⁷:

  
  
  
  
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    The occurrence of malignant melanoma in one or more first- or second-degree relatives.

    
    
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    The presence of numerous (often >50) melanocytic nevi, some of which are clinically atypical.

    
    
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    Many of the associated nevi show certain histologic features (see the following section “Biopsy”).

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  Most DN are compound nevi (Figure 146-1) possessing a junctional and intradermal component (see Chapter 143, Benign Nevi).¹ The junctional component is highly cellular and consists of an irregular distribution of melanocytes arranged in nests and lentiginous patterns along the dermoepidermal junction. The dermal component, located at the center, consists of nests and strands of melanocytes with distinct sclerotic changes.¹

  
  
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  DN exhibit a host response consisting of irregular rete ridge elongation, subepidermal sclerosis, proliferation of dermal capillaries, and a perivascular, lymphohistiocytic inflammatory infiltrate.¹

  
  
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  Individuals with DN may have deficient DNA repair, and DN lesions are associated with overexpression of pheomelanin (pigment produced by melanocytes), which may lead to increased oxidative DNA damage and tumor progression.⁸

Clinical Features

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  Variable mixtures of color including tan, brown, black, and red within a single lesion (Figures 146-4 and 146-5).

  
  
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  Irregular, notched borders; pigment may fade off into surrounding skin.

  
  
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  Flat or slightly raised (Figures 146-4 to 146-6) with the macular portion at edge. Not verrucous or pendulous.

  
  
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  Lesions frequently surrounded by a reddish hue from reactive hyperemia making them appear target-like.

  
  
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  Usually larger than 6 mm; may be larger than 10 mm (Figures 146-1 and 146-4).

  
  
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  Patients with FAMM syndrome may have more than 100 lesions, far greater than the average number of common moles (<50) in most individuals.