Low- and high-risk malignant melanoma--III. Prognostic significance of the resection margin.

The influence of the resection margin on the prognosis of malignant melanoma was investigated in 577 cases (stage I), 285 with later recurrences and 292 disease-free for at least 5 yr. The resection margins varied considerably, with less than or equal to 10 mm in 172 cases and ca. 50 mm in 85 cases. Low- and high-risk melanomas (determined by means of tumor thickness and mitotic index) were found to be distributed evenly, with only minor variations for different resection margins. The occurrence of metastases was found to be independent of the resection margin, and several statistical methods were used (correlation coefficients, chi-square tests, discriminant analyses). This was also true when high-risk cases were analyzed separately. In contrast, for low-risk melanoma (68 cases), the six metastatic cases had a resection margin less than or equal to 20 mm (11.8% vs 0%, P = 0.3). Furthermore, local recurrences (40 in 482 cases) were seen more frequently in cases with a resection margin less than 30 mm (10.0 vs 2.9%, P = 0.02). However, local recurrences did not appear to be responsible for disseminated disease, as 82.1% were at high and 10.3% were at medium risk. The benefit of a 5-cm resection margin could not be substantiated in this study. A 3-cm resection margin may be necessary to lower the risk of local recurrences and a 2-cm margin appeared to be sufficient for low-risk melanoma.