Minimum Safe Pathologic Excision Margins for Primary Cutaneous Melanomas (1-2 mm in Thickness): Analysis of 2131 Patients Treated at a Single Center.

Abstract

This study was designed to determine the minimum safe pathologic excision margin for primary cutaneous melanomas 1.01-2.00-mm thick (T2) and to identify prognostic factors that influence survival in these patients. Several studies have shown previously that "narrow" clinical excision margins (1-2 cm in vivo) are as safe as "wide" excision margins (4-5 cm) for management of primary T2 melanomas. However, pathologic margins are likely to be a better predictor of recurrence than clinical margins. Clinicopathologic and follow-up data for 2131 T2 melanoma patients treated at Melanoma Institute Australia between January 1992 and May 2012 were analyzed. Of the 2131 patients, those who had a pathologic excision margin of <8 mm (equivalent to 1 cm in vivo) had poorer prognosis in terms of disease-free survival compared with the 8-16-mm group (equivalent to 1-2 cm in vivo; P = 0.044). When comparing 8-mm with 16-mm pathologic margins, no differences were observed in any of the survival outcomes. Only the deep margin proved to be an independent predictor of local and in-transit recurrence-free survival (P = 0.003) in all excision margin categories. Pathologic excision margins <8 mm were associated with worse regional node recurrence-free survival and distant recurrence-free survival compared with margins ≥8 mm (P = 0.049 and P = 0.045; respectively). However, these results failed to translate into a statistically significant difference in melanoma-specific survival. The results of this study suggest that if a peripheral/radial pathologic excision margin for a T2 primary cutaneous melanoma is <8 mm consideration should be given to performing a wider excision.