Intracerebral subependymomas. Clinical and neuropathological analyses with special reference to the possible existence of a less benign variant.

The frequency of asymptomatic subependymomas was 0.4% in 1,000 serial routine necropsies and 0.7% in symptomatic subependymomas from 1,000 serial surgical specimens of intracranial neoplasms. Among patients with subependymoma (7 symptomatic and 4 asymptomatic), we found 3 cases of marked nuclear polymorphism (NP) in biopsy specimens. The subjective NP was objectively quantified by computer-assisted morphometry, by which a significant difference in nuclear size between these three cases and other cases (p less than 0.005) was revealed. This morphological characteristic correlated with the results of DNA-analysis by flow fluorescence cytometry (FFCM): subependymomas with NP demonstrated higher S and G2/M phases in a diploid pattern than other benign gliomas of our series. From the clinical data including prognosis, however, no remarkable difference was found between the NP group and other groups. The possible existence of less benign variant should be considered in the diagnosis and treatment of subependymoma.