What are the recommended margins for melanoma in situ?

Surgical Margins for Melanoma In Situ

For standard melanoma in situ, a measured margin of 0.5 cm around the visible lesion is recommended, though for large in situ lentigo maligna melanoma, surgical margins greater than 0.5 cm may be necessary to achieve histologically negative margins. 1

Standard Recommendations by Type

Standard Melanoma In Situ

• 0.5 cm margin around visible lesion (NCCN recommendation) 1
• This recommendation is based on panel consensus rather than prospective clinical trials 1

Lentigo Maligna (Subtype of Melanoma In Situ)

• May require margins greater than 0.5 cm due to characteristic subclinical extension 1
• Studies have consistently shown approximately 50% of patients with lentigo maligna (especially on head and neck) required margins greater than 0.5 cm to achieve clearance 1
• For large lentigo maligna, consider:
  • Staged excision techniques
  • Perimeter excision
  • Contoured excision techniques 1

Special Considerations

Anatomical Location

• Head and neck melanoma in situ often requires wider margins due to subclinical extension 1
• On extremities and trunk, some experts use 1-cm margins for typical melanoma in situ due to:
  • Ease of cosmetic closure
  • Higher likelihood of failure to clear with 0.5-cm margin 1

Margin Adequacy Concerns

• The standard 0.5-cm recommendation has been questioned by research:
  • Zitelli et al. found that 9-mm margins removed 98.9% of melanoma in situ cases, which was significantly better than 6-mm margins (P < .001) 2
  • Traditional bread-loaf sectioning of specimens may miss positive margins, with estimated detection rates of only 58% when sectioning at 1-mm intervals 3

Alternative Approaches When Surgery Is Not Feasible

• Topical imiquimod has emerged as a treatment option, especially for lentigo maligna 1, 4
• Radiotherapy is also used selectively with a recommended target margin of at least 10 mm around the visible lesion 1, 4
• Mohs micrographic surgery may be considered for:
  • Cosmetically sensitive areas (head and neck)
  • When narrow margins are desired 5
  • Has shown 95.1% clearance rates for melanoma in situ 1

Recent Evidence on Recurrence Rates

• A 2024 study found that small melanoma in situ (<10 mm) on low-risk body sites had only 0.9% recurrence rate when excised with 5-mm margins 6
• However, another study showed only 1.1% recurrence following complete excision of all melanoma in situ types, but noted a higher recurrence rate (2.9%) specifically for lentigo maligna subtype 7

Common Pitfalls to Avoid

1. Underestimating subclinical extension: Particularly with lentigo maligna, which may extend several centimeters beyond visible margins 1
2. Relying on standard bread-loaf sectioning: This technique may miss positive margins at the periphery 3
3. Using inadequate margins for high-risk locations: Head, neck, hands, and feet often require wider margins 5
4. Missing foci of invasive melanoma: The central excision specimen should be subject to permanent section analysis to avoid missing invasive components 1

When treating melanoma in situ, surgical excision remains the standard of care, with margins tailored to the subtype and anatomical location, prioritizing complete removal to prevent recurrence and progression to invasive disease.