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What is the margin of excision necessary for a malignant melanoma with an invasion of 2.5mm?
The answer is 3cm.
Surgical removal of primary malignant melanomas is still the treatment of choice. Once the diagnosis has been made, re-excision is necessary or a 40 % local recurrence is expected. Originally, it was thought that a margin of 5cm was necessary on all re-excisions, but further research revealed that the risk of recurrence is directly related to the depth of invasion. The table below illustrates this correlation.
A 4% local recurrence rate is observed using the above table.
References:
1. Cameron, RB et al, Practical Oncology, pp118-132, Appleton and Lange, 1994