The resolution of discrepancies in the reported incidence of primary brain tumors.

Population-based morbidity studies of primary intracranial neoplasms reveal a general pattern of age-specific incidence: a small childhood peak, followed by a taller peak between ages 50 and 80. One notable exception is Rochester, Minnesota, where there is a sustained increase in incidence with increasing age, together with higher age-specific rates than seen in data from other locations. Comparing data from Rochester and Connecticut reveals that the larger percentage of cases first diagnosed at autopsy in Rochester accounts in large part for these discrepancies and suggests that a substantial number of brain tumors remain undiagnosed in the elderly during life.