[Occurrence of lung cancer in Denmark 1943-1986. Reliability of the cancer registry].

A rise in the number of adenocarcinomas of the lung and a fall in squamous cell carcinomas are seen in Denmark since 1978; a change based on a growing number of lung cancers among women with an excess of adenocarcinomas. A fall in the frequency of autopsies in Denmark will entail the loss of an essential control of the quality of diagnosis of lung cancer, primary or secondary, and make future descriptive studies difficult to interpret. The validity of morphologic diagnosis of lung cancer as recorded by the Danish Cancer Registry during 1943-1986 was assessed. We extracted a stratified random sample of 5% of all recorded cases prior to 1978, these were then recorded according to the ICD-O classification. Cases after 1978 were originally coded in the Registry according to ICD-O, here we checked the coding against the original reports. The information on morphology prior to 1978 was too inprecise to merit evaluation of trends and proportionate distributions by morphology. After 1978 data was adequate, and after 1983 very precise.