[Thymomoa in Denmark]

This is a descriptive study of thymomas notified to the national Danish Cancer Registry and registered by the departments of pathology during the years 1943-1993. A total of 433 cases of benign and malignant thymomas were included over these 50 years with an increase of the incidence to a stable rate of 2.5/million/year from start to 1973. The male:female ratio is 1:1. While the age-specific incidence rate for persons below 40 years is constantly low throughout the period of investigation, a doubling of the rate is registered for persons between 70 and 79 during the period 1978-1993. The incidence rate in Copenhagen is much higher compared to other regions of Denmark. The above-mentioned increase in incidence is due mainly to an underreporting of benign thymomas during the first period of investigation (1943-1977), but may also be due to improved diagnostic capabilities and to more uniform methods of registration during the last period (1978-1993).