What are the recommended margins of excision for a patient with melanoma?

Recommended Surgical Excision Margins for Melanoma

For melanoma excision, use 0.5 cm margins for in situ disease, 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. These recommendations are based on multiple prospective randomized trials showing no survival benefit with wider margins 1, 2.

Margin Recommendations by Breslow Thickness

Melanoma In Situ

• Use 0.5 cm clinical margins to achieve complete histological excision 1, 2
• For lentigo maligna melanoma in situ, particularly on the head and neck, margins >0.5 cm are frequently necessary to achieve histologically negative margins due to unpredictable subclinical extension 1, 2
• Consider staged excision techniques or Mohs micrographic surgery for lentigo maligna, especially in cosmetically sensitive areas, with studies showing 95.1% clearance rates 3

Melanomas ≤1.0 mm (T1)

• Use 1 cm margins (Category 1 recommendation) 1, 2
• This is supported by the WHO trial of 612 patients showing no difference in local recurrence or survival between 1 cm and 3 cm margins at 90-month follow-up 1, 4
• A large case-control study of 11,290 thin melanomas demonstrated that margins <8 mm histologic (corresponding to <1 cm clinical) were associated with increased local recurrence risk 5
• No local recurrences occurred in patients with melanomas <1 mm treated with 1 cm margins in the WHO trial 1, 4

Melanomas 1.01-2.0 mm

• Use 1-2 cm margins (Category 1 recommendation) 1, 2
• The WHO trial showed similar outcomes between 1 cm and 3 cm margins, though 4 patients with 1-2 mm melanomas developed local recurrence as first relapse, all in the 1 cm margin group 1
• The Swedish Melanoma Study Group trial of 769 patients with 0.8-2.0 mm melanomas found no significant differences in local recurrence, regional recurrence, or survival between 2 cm and 5 cm margins at median 5.8-year follow-up 6
• A 2 cm margin is preferred when functionally and cosmetically feasible 1

Melanomas 2.01-4.0 mm

• Use 2 cm margins (Category 1 recommendation) 1, 2
• The National Intergroup Trial of 468 patients showed no differences in local recurrence, disease-free survival, or overall survival between 2 cm and 4 cm margins at 10-year follow-up 1
• Margins >2 cm are inappropriate for this thickness category 1

Melanomas >4.0 mm

• Use 2 cm margins (Category 2A recommendation) 1, 2
• A recent prospective randomized trial comparing 1 cm versus 3 cm margins for melanomas >2 mm showed wider margins were associated with slightly lower combined local/regional/nodal recurrence but no improvement in local recurrence alone or melanoma-specific survival 1
• Evidence is less robust for this thickness category, but 2 cm margins remain the standard 1

Critical Clinical Considerations

Anatomically Difficult Locations

• Margins may be modified for anatomic or cosmetic considerations, particularly on the face, distal extremities, hands, feet, and ears 1, 2
• In these locations, 1.0-2.0 cm margins may be acceptable when a full 2.0 cm margin would be difficult to achieve 1
• For head and neck melanomas, consider that wider margins may be needed—one Mohs surgery study recommended minimum 1.5 cm margins for these locations 7

Timing of Wide Excision

• Perform definitive excision within 2-6 weeks after biopsy to allow complete pathologic assessment and coordinate sentinel lymph node biopsy when indicated 8
• If sentinel lymph node biopsy is indicated, it must be performed before or concurrent with wide excision to avoid disrupting lymphatic drainage patterns 8

Important Margin Interpretation

• Clinical/surgical margins do not necessarily correlate with histologic margins measured by pathologists 1, 2
• The margins discussed refer to those taken at surgery, measured from the visible lesion or biopsy scar 1

Common Pitfalls and How to Avoid Them

Inadequate Initial Biopsy

• Ensure the initial biopsy was full-thickness and adequate for microstaging 8
• Shallow shave biopsies may underestimate true Breslow depth, leading to inadequate surgical planning 8
• If microstaging is inadequate, perform narrow margin re-excision before definitive treatment 1

Lentigo Maligna Recurrence

• Lentigo maligna has high recurrence rates with standard margins due to subclinical extension that can extend several centimeters beyond visible margins 1
• Approximately 50% of melanoma in situ on the head and neck require margins >0.5 cm to achieve clearance 2
• Use techniques for exhaustive histologic margin assessment or consider staged excision/Mohs surgery for these lesions 1, 3

Melanomas 1-2 mm Thickness

• While 1 cm margins are acceptable, be cautious as all local recurrences in the WHO trial occurred in the 1 cm margin group for this thickness category 1
• Discuss margin choice with the multidisciplinary team and patient, but use minimum 1 cm margins where functionally and cosmetically sensible 1

Avoiding Excessive Margins

• Do not use margins >2 cm for any melanoma, as multiple randomized trials show no benefit and increased morbidity 1
• The National Intergroup Trial definitively showed margins >2 cm are inappropriate for melanomas 1-4 mm thick 1