Risk factors predicting positive margins at primary wide local excision of cutaneous melanoma

BACKGROUND A small percentage of patients will have positive histological margins after primary wide local excision (WLE) of cutaneous melanoma (CM). Risk factors that predict marginal involvement at WLE remain unclear. OBJECTIVE To identify risk factors associated with positive margins after WLE of CM. MATERIALS AND METHODS A retrospective review of patients treated at a single institution for CM with sentinel lymph node biopsy from 1997 to 2011 was conducted. RESULTS Positive margins occurred in 6% of patients. Patients with positive margins were older (72.4 vs 60.7, p <.001), had thicker tumors (3.6 vs 1.9 mm, p <.001), and often involved the head and neck region (p <.001). Patients with positive margins at WLE had positive margins on initial biopsy (p .012) and a higher rate of a melanoma in situ component on initial biopsy (24% vs 11%, p .02). The 5-year local recurrence rate was significantly different between those with positive and negative margins at WLE (16.0% vs 6.9%; p .047). CONCLUSION Positive margins after WLE are uncommon. When a patient has multiple risk factors for positive margins at WLE, histologically clear margins should be obtained through mapped serial excision or Mohs micrographic surgery.