Resection Margins in Merkel Cell Carcinoma: Is a 1-cm Margin Wide Enough?

Background Guidelines regarding specific resection margins for primary Merkel cell carcinoma (MCC) are not well established. The current National Comprehensive Cancer Network (NCCN) guidelines recommend 1- to 2-cm resection margins. This study aimed to determine the impact of margin width on local recurrence (LR), disease-specific survival (DSS), overall survival (OS), and type of wound closure. Methods All patients who underwent resection of primary MCC at a single institution from 2000 to 2015 were reviewed. Patient demographics, clinicopathologic characteristics, treatments, and outcomes were reviewed. Results A total of 240 patients underwent resection of primary MCC with resection margin width identified in the operative report. The median age was 76 years, and 65.8% of the patients were men. Of the 240 patients, 85 (35.4%) had head and neck primaries, 140 (58.3%) had extremity primaries, and 15 (6.3%) had trunk primaries. In terms of margins, 69 patients (28.8%) had a margin of 1 cm, 36 patients (15%) had a margin of 1.1–1.9 cm, and 135 patients (56.2%) had a margin of 2 cm or more. The median follow-up period was 21 months. The LR rate was 2.9% for a margin of 1 cm, 2.8% for a margin of 1.1–1.9 cm, and 5.2% for a margin of 2 cm or more ( p = 0.80). The 5-year OS was 63.6% for a margin of 1 cm, 59.7% for a margin of 1.1–1.9, and 70.7% for a margin of 2 cm or more ( p = 0.66). The 5-year DSS was 80.3% for a margin of 1 cm, 66.2% for a margin of 1.1–1.9 cm, and 91.8% for a margin of 2 cm or more ( p = 0.28). For wound closure, 43.5, 50, and 65.9% of the patients respectively required a flap or graft with a margin of 1, 1.1–1.9, and 2 cm or more ( p = 0.006). Conclusions A 1-cm resection margins did not increase the risk of LR. Margin width did not make a significant difference in DSS or OS. Larger resection margins increase the need for a graft or flap closure.