What is the next step in managing a melanoma that is 0.72 mm in depth with an initial excision showing a 1mm free margin?

Management of Thin Melanoma (0.72 mm in Depth)

For a melanoma that is 0.72 mm in depth with an initial excision showing a 1mm free margin, the next appropriate step is re-excision with a 1 cm margin. 1

Rationale for 1 cm Margin Re-excision

The management of this melanoma is guided by its Breslow thickness of 0.72 mm, which classifies it as a thin melanoma (≤1.0 mm). Multiple high-quality guidelines provide clear recommendations for this scenario:

• The NCCN guidelines specifically recommend a 1.0 cm margin for stage IA melanomas (≤1.0 mm in thickness) as a category 1 recommendation, indicating high-level evidence and uniform consensus 1
• The UK guidelines similarly recommend a 1 cm margin for melanomas less than 1 mm in depth, supported by level A, grade I evidence 1
• The French guidelines also recommend a 1 cm margin for melanomas with Breslow thickness ≤1 mm 1

Why 1 cm is Sufficient

The recommendation for a 1 cm margin is based on several prospective randomized trials that have shown:

• For thin melanomas (≤1.0 mm), a 1 cm margin provides equivalent local control and survival outcomes compared to wider margins 1
• No local recurrences were observed in patients with melanomas less than 1 mm in depth with 1 cm excision margins in key studies 1
• Wider margins (2-3 cm) have not demonstrated improved survival or local control for thin melanomas 1

Why Other Options Are Not Appropriate

1. 2 cm margin excision: This is excessive for a melanoma of 0.72 mm thickness and is not supported by evidence. Guidelines reserve 2 cm margins for melanomas >2.0 mm in thickness 1

2. Inguinal lymph node excision: This is not indicated for a thin melanoma without clinical evidence of nodal involvement. Prophylactic nodal dissection is not recommended for isolated cutaneous melanoma 1

3. Observation and follow-up only: This is insufficient as the initial excision had only a 1 mm free margin, which does not meet the recommended 1 cm margin for definitive treatment 1

Sentinel Lymph Node Biopsy Considerations

While not specifically mentioned in the options, it's worth noting that sentinel lymph node biopsy (SLNB) may be considered for select patients with thin melanomas:

• For melanomas ≥0.8 mm, SLNB may be justified as studies have shown that approximately 35% of patients with melanomas 0.80-0.99 mm thick developed lymph node recurrence 2
• However, for a 0.72 mm melanoma without other high-risk features, SLNB is generally not indicated 1

Common Pitfalls to Avoid

1. Undertreatment: Simply observing a thin melanoma with inadequate margins (only 1 mm) risks local recurrence

2. Overtreatment: Performing extensive surgery (2 cm margins or lymph node dissection) for thin melanomas increases morbidity without improving outcomes

3. Neglecting histologic features: While thickness is the primary determinant of margin width, other features like ulceration or high mitotic rate may influence risk assessment, though not the margin recommendation itself 1

The evidence clearly supports re-excision with a 1 cm margin as the appropriate next step for this 0.72 mm melanoma with an initial 1 mm free margin.