What is the treatment for evolving melanoma in situ?

Treatment of Evolving Melanoma In Situ

Surgical excision with a margin of 0.5 to 1.0 cm is the standard first-line treatment for melanoma in situ, with complete histological clearance being the primary goal to prevent progression to invasive melanoma. 1

Surgical Management Options

Standard Wide Excision

• For typical melanoma in situ: 0.5-1.0 cm margins 1
• For lentigo maligna type (LM): May require wider margins to achieve histological clearance due to subclinical extension 1
• Depth of excision should extend to but not include the fascia 1

Special Considerations for Different Anatomical Locations:

Head and Neck/Cosmetically Sensitive Areas:

• Mohs micrographic surgery (MMS) or staged excision with permanent sections is recommended 1
• For lentigo maligna on face, ears, or scalp:
  • Staged excision techniques allow for comprehensive margin assessment while preserving tissue 1
  • Permanent section analysis of the central specimen is essential to identify potential invasive melanoma 1

Trunk and Extremities:

• 1 cm margins are often preferred due to:
  • Ease of cosmetic closure
  • Higher likelihood of clearing the melanoma in situ compared to 0.5 cm margins 1

Alternative Approaches When Surgery Is Not Feasible

For patients where surgery is contraindicated or impractical:

• Radiotherapy: Viable alternative with approximately 5% local failure rate 2
• Topical imiquimod 5% cream: Complete clinical clearance rate of 75-90% 2
• CO2 laser or cryotherapy: May be considered in select cases 1

Important Clinical Considerations

Risk of Subclinical Disease

• Studies show that 5 mm margins may be inadequate in many cases:
  • Only 86% of melanoma in situ cases were successfully excised with 6 mm margins
  • 9 mm margins removed 98.9% of melanoma in situ 3
  • Lentigo maligna type has higher rates of incomplete excision 4

Risk of Occult Invasion

• Up to 12% of lesions diagnosed as melanoma in situ may contain invasive melanoma upon complete excision 5
• This reinforces the importance of adequate full-thickness biopsies before surgical management

Recurrence Risk

• Complete excision with adequate margins results in very low recurrence rates:
  • Recent data shows only 0.9% recurrence rate for small (<10 mm) melanoma in situ lesions on low-risk sites with 5 mm margins 6
  • Lentigo maligna has higher recurrence rates (2.9%) even after complete excision 4

Follow-up Recommendations

• Lifelong annual follow-up is recommended to detect potential recurrence or new primary melanomas 1
• Self-surveillance should be encouraged through patient education 1
• Clinical examination remains the standard for surveillance 1

Treatment Algorithm

1. Confirm diagnosis with adequate biopsy
2. Assess patient factors: age, general health, lesion location and size
3. Select surgical approach:
   • Standard melanoma in situ: Wide excision with 0.5-1.0 cm margins
   • Lentigo maligna on face/head/neck: Consider Mohs or staged excision
   • Large lesions or anatomically sensitive areas: Consider specialized techniques
4. Confirm histological clearance of all margins
5. Implement lifelong surveillance with annual skin examinations