Wide Local Excision (Melanoma)
What the Examiner Expects
Definitive surgical excision of cutaneous melanoma with appropriate margins based on tumor thickness. The examiner expects you to know the margin guidelines derived from prospective randomized trials: melanoma in situ requires 0.5–1 cm margins, tumors ≤ 1.0 mm require 1 cm, tumors 1.01–2.0 mm require 1–2 cm, and tumors > 2.0 mm require 2 cm radial margins. The excision extends down to but NOT including the underlying deep fascia. Sentinel lymph node biopsy is indicated for melanomas ≥ 0.8 mm Breslow depth, or for thinner melanomas with high-risk features (ulceration, mitotic rate ≥ 1/mm², lymphovascular invasion).
Key Examiner Focus Points
- Margins based on Breslow thickness: in situ (0.5–1 cm), ≤ 1 mm (1 cm), 1.01–2 mm (1–2 cm), > 2 mm (2 cm)
- Excision down to but not including the deep fascia
- Concurrent sentinel lymph node biopsy for tumors ≥ 0.8 mm Breslow depth
- Subungual melanoma may require digit amputation
- Margins are measured clinically from the visible edge of the melanoma or biopsy scar
Common Curveballs
Melanoma is on the face — a 2 cm margin would cause significant cosmetic deformity
In cosmetically sensitive or functionally critical locations (face, digits), narrower margins may be accepted. Mohs micrographic surgery with complete margin assessment is an alternative for melanoma in situ or lentigo maligna on the face. For invasive melanoma, a multidisciplinary approach with plastic surgery for reconstruction is appropriate.
Sentinel lymph node biopsy is positive — what is the next step?
Per MSLT-II and DeCOG-SLT trials, completion lymph node dissection (CLND) is no longer mandatory for all positive SLNs. Observation with ultrasound surveillance of the nodal basin is acceptable for micrometastatic disease. CLND may be considered for high-volume nodal disease. Adjuvant systemic therapy (immunotherapy — nivolumab/pembrolizumab, or targeted therapy — BRAF/MEK inhibitors if BRAF mutated) should be discussed.
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