OBJECTIVE. Three previous retrospective studies noted a positive association between birthmarks and childhood cancer. The objective of this study was to determine whether the incidence of cancer is increased in children with birthmarks relative to those without birthmarks using data from the Collaborative Perinatal Project cohort, a large, prospective study.

METHODS. Our study population comprised 49503 US children who were born between 1959 and 1968. Birthmarks were documented as definite or suspected during the first year through history or medical examinations and included hemangiomas (port-wine, strawberry, or cavernous), pigmented nevi, lymphangiomas, and café-au-lait spots. The association between birthmarks and childhood cancer was determined using Cox proportional hazards regression.

RESULTS. In the Collaborative Perinatal Project, 2505 individuals had a documented definite or suspected birthmark, including 7 of 47 children who developed cancer. Birthmarks were associated with a significant increase in the risk for cancer. There was a slight attenuation of the risk estimate when cases that were diagnosed in the first year of life were excluded. No specific childhood malignancies were notably affected by birthmarks.

CONCLUSIONS. Although this study was based on a small number of cases, we found birthmarks to be in excess in children who received a diagnosis of cancer using prospective data. These findings provide additional support for the possibility of a shared etiology between birthmarks and childhood cancer that could offer insight into the pathogenesis of pediatric malignancy.

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