Recurrence Patterns after Primary Excision of Invasive Melanoma with Melanoma in situ at the Margin

The significance and management of melanoma in situ (MIS) at the margin of excision of invasive melanoma is debated. Patients undergoing excision of invasive melanoma from 2000 to 2016 with MIS at the margin were identified. A cohort without MIS was matched for age, gender, location, and Breslow depth. Thirty-two patients with 33 cases of MIS at the margin were identified. Melanoma was located on the head/neck (66.7%), extremities (24.2%), and trunk (9.1%). Median Breslow depth was 1.0 mm (range 0.25-10.80). Margin treatment included re-excision (45.5%), re-excision plus imiquimod (3.0%), imiquimod alone (9.1%), and observation alone (42.4%). At a median follow-up of 91 months (range 28-126), five patients (15.2%) with a median Breslow depth of 4.75 mm (range 1.10-6.70) developed local recurrence (LR). Three underwent re-excision of the positive margin and two were observed. Intervention for positive margins did not decrease LR compared with observation (P = 0.905, OR = 1.125, 95% confidence interval [CI] 0.162-7.824). All five patients with LR were alive at the last follow-up. There were two recurrences in the matched cohort (6.1%); both were alive at the last follow-up. Risk of LR is higher with MIS at the margin, but this does not seem to impact survival. Larger studies may elucidate predictive factors and interventions that decrease risk for LR.