One in a hundred million: Merkel cell carcinoma in pediatric and young adult patients is rare but more likely to present at advanced stages based on US registry data.

Published data for pediatric and young adult patients with Merkel cell carcinoma (MCC) are scarce. Case reports from the United States and Europe suggest that MCC can occur in young persons and may be more aggressive in this setting. We sought to determine the frequency of MCC in pediatric and young adult populations and establish whether MCC is more likely to present at advanced stages in younger people. To minimize referral bias and maximize available data, we used the National Program of Cancer Registries Surveillance Epidemiology and End Results (NPCR SEER) database, which captures incident cancer cases in more than 98% of the US population.