Width of excision

After the excision biopsy for diagnosis and measurement of microscopic Breslow thickness, a wider and deeper margin is taken to make certain that the primary lesion is completely removed and also micrometastases if any (1).

• lateral surgical excision margins for invasive melanoma is based on the Breslow thickness
• the depth of excision has conventionally been to the muscle fascia or deeper (1)
• the recommended surgical margins are those measured clinically at the time (rather than the histopathological margins)
  • the final decision is affected by the functional and cosmetic implications of the margin chosen and is made by the multidisciplinary team (MDT) after discussion with the patient
  • adequacy of excision should be confirmed subsequently by review of re-excision histology, making an adjustment for an average shrinkage of 20%

Traditionally the width of excision of a malignant melanoma was 3 to 5cm (2).

• however, there has been evidence in the treatment of melanomas of less than 2mm thickness that there are no differences in local, regional or metastatic spread with thin lesions excised with 1cm or more than 3cm margin (3).
• in patients with high risk malignant melanoma (>=2mm thick), primary tumour excision with a surrounding margin of 3cm was more effective than a margin of 1cm for reducing recurrence However the study did not reveal any difference for all cause mortality between the two groups (4).

NICE guidance states (5):

Excision for stages 0 to II melanoma

• consider a clinical margin of at least 0.5 cm when excising stage 0 melanoma
• if excision for stage 0 melanoma does not achieve an adequate histological margin, discuss further management with the specialist skin cancer multidisciplinary team
• use a clinical margin of:
  • 1 cm when excising stage I melanoma or when a 2 cm excision margin would cause unacceptable disfigurement or morbidity
  • 2 cm when excising stage II melanoma. The clinical margin should be around the histological biopsy scar and take into account the primary melanoma margin

Reference:

• (1) Marsden JR et al. Revised U.K. guidelines for the management of cutaneous melanoma 2010. Br J Dermatol. 2010;163(2):238-56
• (2) Clark, W. et al (1969).The histogenesis and biologic behaviour of primary human malignant melanomas of the skin. Cancer Res;29:705-26.
• (3) Veronesi, U. et al (1998).Thin stage I primary cutaneous malignant melanoma.NEJM ;318:1159-62.
• (4) Thomas JM et al (2004). Excision margins in high-risk malignant melanoma. NEJM;350:757-66
• (5) NICE (July 2022). Melanoma: assessment and management