Recommended Surgical Margins for Melanoma Excision
The recommended surgical excision margins for melanoma are determined by the Breslow thickness of the tumor, with 0.5 cm margins for melanoma in situ, 1 cm margins for melanomas ≤1.0 mm thick, 1-2 cm margins for melanomas 1.01-2.0 mm thick, and 2 cm margins for melanomas >2.0 mm thick. 1
Margin Recommendations Based on Tumor Thickness
Melanoma in situ: 0.5 cm margin around the visible lesion 1
- For large in situ lentigo maligna melanoma, surgical margins greater than 0.5 cm may be necessary to achieve histologically negative margins 1
Melanomas ≤1.0 mm thick (Stage IA): 1.0 cm margin (category 1 recommendation) 1
Melanomas 1.01-2.0 mm thick: 1.0-2.0 cm margin (category 1 recommendation) 1
Melanomas >2.0 mm thick: 2.0 cm margin 1
Special Considerations
Lentigo maligna melanoma: May require wider margins due to characteristic subclinical extension of atypical junctional melanocytic hyperplasia that can extend several centimeters beyond visible margins 1
- Various approaches with meticulous margin control have shown high local control rates 1
Anatomically difficult areas: Margins may be modified to accommodate individual anatomic or cosmetic considerations 1
- 1.0-2.0 cm margins might be acceptable in areas where a full 2.0-cm margin would be difficult to achieve 1
Head and neck melanomas: May benefit from narrower margins (1 cm) for melanomas 1.01-2.0 mm thick to decrease the need for grafts/flaps 2
Evidence from Clinical Trials
The WHO international prospective study randomized 612 patients with melanomas ≤2.0 mm to wide excision with either 1.0 or 3.0 cm margins. At median follow-up of 90 months, both groups had similar rates of local recurrence and disease-free and overall survival 1
The National Intergroup Trial randomized 468 patients with melanomas 1.0-4.0 mm in thickness to wide excision with either 2.0 or 4.0 cm margins. At median follow-up of 10 years, no differences were seen in local recurrence, disease-free survival, or overall survival 1
A more recent prospective randomized trial comparing 1 versus 3 cm margins for melanomas thicker than 2 mm showed wider margins were associated with a slightly lower rate of combined local/regional/nodal recurrence, but without improvement in local recurrence alone or melanoma-specific survival 1
However, a long-term follow-up study published in 2016 found that for melanomas >2 mm in thickness, 1 cm margins were associated with higher melanoma-specific mortality compared to 3 cm margins, suggesting that 1 cm margins may be inadequate for these thicker melanomas 3
Important Clinical Considerations
Surgical margins should not be less than 1 cm around primary melanoma (except for melanoma in situ) 1
Clinical/surgical margins do not necessarily correlate with gross pathologic/histologic margins 1
Sentinel lymph node biopsy (SLNB) should be discussed for melanomas ≥1 mm thickness, and lymphoscintigraphy must be performed before wider excision of the primary melanoma site 4
Although surgical excision remains standard care for in situ melanoma, topical imiquimod has emerged as a treatment option in cases where surgery is not feasible due to comorbidity or cosmetically sensitive tumor location, especially for lentigo maligna 1
Common Pitfalls to Avoid
Inadequate margins for lentigo maligna melanoma - studies have shown that approximately 50% of patients with melanoma in situ on the head and neck required margins greater than 0.5 cm to achieve clearance 1
Using narrower margins than recommended for thick melanomas (>2 mm) - evidence suggests this may lead to higher rates of melanoma-specific mortality 3
Failing to perform SLNB before wide excision in eligible patients, which can disrupt lymphatic drainage patterns 4
Not considering staged excision techniques for melanomas in cosmetically sensitive areas, particularly for lentigo maligna on the head and neck 1