Does a mildly atypical nevus (mole) need to be completely excised?

Management of Mildly Atypical Nevi

Complete excision of mildly atypical nevi is generally unnecessary, as studies document low short-term recurrence rates and no progression to melanoma in incompletely excised lesions with mild to moderate atypia. 1

Risk Assessment for Atypical Nevi

• Mildly atypical nevi have a very low risk of transformation to melanoma, with studies showing no melanoma development in incompletely excised atypical nevi followed for 5+ years 1
• Local recurrence rates are minimal (approximately 3.6% over 2 years) for incompletely excised nevi with mild to moderate atypia 1
• The risk of clinically significant change in diagnosis after excision of mildly or moderately dysplastic nevi is extremely low (1.6% in one study) 2
• Atypical nevi are frequently diagnosed using shave biopsy or other procedures that may result in positive histologic margins 1

Management Algorithm Based on Degree of Atypia

For Mildly Atypical Nevi:

• Observation is an acceptable alternative to re-excision, particularly when:
  • The patient has multiple other atypical nevi 1
  • The lesion shows only mild atypia 1, 3
  • Clinical margins appear normal even if histologic margins are positive 2

For Moderately Atypical Nevi:

• Observation may still be reasonable if:
  • The patient has multiple other similar lesions 1
  • The lesion was mostly removed during initial biopsy 1
• Consider conservative re-excision (2-5 mm margins) if:
  • The lesion is the patient's only atypical nevus 1
  • Patient preference leans toward complete removal 4

For Severely Atypical Nevi:

• Complete surgical excision is recommended due to:
  • Higher association with melanoma 2
  • Insufficient long-term data on observation 1
  • Conservative re-excision with 2-5 mm margins is typically adequate 1

Technical Considerations for Removal

• If complete removal is desired, a 2-mm margin of normal-appearing skin has been shown to achieve clear histopathologic margins in 87.2% of dysplastic nevi 5
• Avoid diagnostic shave biopsies for suspicious lesions as they may lead to incorrect diagnosis due to sampling error 1, 4
• Partial removal of melanocytic nevi may result in pseudomelanoma (clinical and pathological picture resembling melanoma) 1, 4

Follow-up Recommendations

• Regular self-examination should be taught to patients with atypical nevi 4
• Clinical and dermoscopic follow-up is appropriate for observed lesions with mild atypia 4, 3
• Concerning changes that warrant immediate evaluation include:
  • Rapid growth or darkening 4, 6
  • Bleeding or ulceration 6
  • Development of nodules or color variegation 6

Special Considerations

• Location matters: atypical genital nevi may have worrisome histologic features but typically follow a benign clinical course 7
• For melanomas arising in an atypical nevus, ensure removal of both the melanoma with appropriate margins and the entirety of the residual nevus 1, 4
• Photography is recommended to document baseline appearance and track changes over time for any observed atypical nevi 6