Atypical Nevus

Atypical Nevus

• Atypical nevi are highly variable in appearance. The same ABCDE criteria used to distinguish melanoma from banal nevi also characterize atypical nevi:
  • A—asymmetry
  • B—border irregularity
  • C—color variegation
  • D—diameter greater than 6 mm
  • E—evolutionary behavior (e.g., changing, itching)
• The treatment of atypical nevi is not standardized. In persons with numerous clinically atypical nevi, a dermatologist may biopsy only those with a history of change, or only those with an appearance considerably different from others (the “ugly duckling sign”). The biopsy technique used may vary based on the clinical situation.
• It has been estimated that the risk of an atypical nevus becoming a melanoma is about 1:10,000 per year. In patients with sporadic atypical nevi, there may be up to a 15-fold elevated lifetime increased risk of melanoma. In patients with FAMMM syndrome, the risk may be increased 200- to 1200-fold.

Terminology

• The terminology surrounding atypical nevi is not standardized. Alternative nosology includes dysplastic nevi, Clark nevi, and nevi with cytologic atypia and architectural disorder.

Etiology and Risk Factors of Atypical Nevus

• The pathogenesis of atypical nevi is poorly understood. It is likely that the development of atypical nevi involves a complex interaction of genetic factors and sunlight exposure. In about one-third of patients with familial atypical moles and melanoma syndrome (FAMMM syndrome), there are germline CDKN2A mutations. The pathogenesis of other forms of familial atypical nevi and sporadic atypical nevi is poorly established.
• Atypical nevi usually appear first in adolescence or early adulthood.

How is this condition diagnosed?

Approach to Diagnosis

• Assessment of any particular nevus as clinically atypical is established by the physical examination.

Workup

History

• Familial atypical nevus syndromes are established through physical exam and queries regarding a personal and/or family history of melanoma. Melanoma in a first-degree relative (parent, sibling, child) is considered significant.

Physical Examination

• Atypical nevi may be solitary, few, or numerous (>200).
• The trunk is usually affected by atypical nevi, especially the back. The chest, abdomen, and proximal extremities may also be involved. Sun-protected sites, such as the buttocks, often have fewer atypical nevi.
• Atypical nevi are usually larger than common banal nevi, with most of them being more than 5 mm in diameter.
• Atypical nevi are highly variable in appearance. The same ABCDE criteria used to distinguish melanoma from banal nevi also characterize atypical nevi:
  • A—asymmetry
  • B—border irregularity
  • C—color variegation
  • D—diameter greater than 6 mm
  • E—evolutionary behavior (e.g., changing, itching)

Diagnostic Procedures

• Histologic assessment of an atypical nevus, and exclusion of melanoma, occurs by biopsy.

How is Atypical Nevus treated?

Approach to Treatment

• The treatment of atypical nevi is not standardized. In persons with numerous clinically atypical nevi, a dermatologist may biopsy only those with a history of change, or only those with an appearance considerably different from others (the “ugly duckling sign”). The biopsy technique used may vary based on the clinical situation.

Nondrug and Supportive Care

• Patients with sporadic or familial atypical nevus syndromes need to be educated in self-examination and have periodic skin exams with a health professional (usually every 6–12 months).

Treatment Procedures

• The management of biopsy-proven atypical nevi with involved surgical margins is not standardized. Some dermatologists remove all atypical nevi completely, whereas others completely remove only those with moderate or severe degrees of atypia.
• Serial photographs and computerized mole mapping have been advocated, but the utility of these measures has been questioned by some. The techniques are also not standardized.

References

• Duffy K, et al. The dysplastic nevus: from historical perspective to management in the modern era: part I. Historical, histologic, and clinical aspects. Journal of the American Academy of Dermatology. 2012;67(1):1-16. Reference 
• Duffy K, et al. The dysplastic nevus: from historical perspective to management in the modern era: part II. Molecular aspects and clinical management. Journal of the American Academy of Dermatology. 2012;67(1):19-32. Reference