The prognosis of melanoma patients who are diagnosed with multiple primary lesions remains controversial. We used a large population-based cohort to re-examine this issue, applying a delayed entry methodology to avoid survival bias. Of 32,238 eligible patients diagnosed between 1995 and 2008, 29,908 (93%) had a single invasive melanoma, 2,075 (6%) had two, and 255 (1%) had three. Allowing for differences in entry time, 10-year cause-specific survival for these three groups was 89% (95% confidence interval [CI] = 88–90%), 83% (95% CI = 80–86%), and 67% (95% CI = 54–81%), respectively.
