BACKGROUND: Analysis conducted in the Life Span Study (LSS) cohort of atomic 
bomb survivors in Hiroshima and Nagasaki found a significant dose-related excess 
of tumors of the central nervous system (CNS) and the pituitary gland. The 
objective of the current study was to evaluate clinical and epidemiologic 
characteristics of first primary tumors of the CNS and the pituitary gland in 
this cohort and to compare them with characteristics among other populations.
METHODS: CNS and pituitary gland tumors that were diagnosed between 1958 and 
1995 among 80,160 LSS cohort members were ascertained through Hiroshima and 
Nagasaki tumor registries, autopsy reports, and other sources. Pathologists 
reviewed all available records and slides to verify histologic diagnoses. 
Poisson regression analysis was used to model background incidence rates 
allowing for radiation effects.
RESULTS: Meningioma was the most common tumor among clinically diagnosed tumors, 
followed by neuroepithelial tumor, schwannoma, and pituitary tumor. The overall 
incidence of these tumors increased initially with age but declined among the 
elderly. For all age groups and for both genders, incidence increased over time. 
By contrast, when tumors diagnosed at autopsy were included, incidence rose 
continuously with age and was stable over time.
CONCLUSIONS: The main characteristics of CNS and pituitary gland tumors 
diagnosed in the LSS cohort were consistent with the characteristics of 
"spontaneous" tumors observed in other population-based studies. The 
predominance of meningiomas over neuroepithelial tumors in the Japanese 
population was noteworthy and warrants further investigation. The secular rise 
in incidence of all clinically diagnosed CNS and pituitary gland tumors is most 
likely to be attributable to the increased use of new imaging techniques.