Introduction: The aim of this study was to evaluate the registration of childhood CNS tumours in the Danish Cancer Registry (CR) from 1980 to 1996, based on completeness and validity.
Materials and methods: The completeness of the CR was estimated by examination of the Danish National Hospital Register and an independent hospital registry. To determine the validity of the CR, 640 cases of childhood CNS tumours identified in the CR were compared with the corresponding medical record, with regard to cancer morphology and date of diagnosis.
Results: The completeness of the CR was 98-99%. For 82% of all cases, the morphology registered in the CR was identical with that in the medical record. The validity of the morphological diagnosis was 84% for astrocytomas, 88% for ependymomas, 95% for medulloblastomas, 47% for other gliomas and 76% for miscellaneous intracranial and intraspinal neoplasms. In a further 7% of all cases, the morphological diagnosis in the CR was incorrect with respect to details but correct within these main diagnostic groups, 6% were tumours of another main diagnostic group than that registered in the CR and 5% were not tumours, were tumours outside the study criteria or were registered in the hospital journal as suspected tumours. The date of diagnosis in the CR and that in the medical records were concordant in 88% of the evaluated cases.
Conclusion: Registration of childhood CNS tumours in the CR was highly complete, while the validity of the morphological diagnosis differed among the main diagnostic groups. The relatively low validity might be explained by the anatomic location of CNS tumours, which makes tissue sampling for histological verification and therefore diagnosis difficult.