Long-term survival after malignant glioma. A clinical and histopathological study on the accuracy of the diagnosis in a population-based cancer register.

The Stockholm Regional Cancer Register (SRCR) contains 1,002 patients with malignant glioma reported between 1958 and 1977. A total of 49 patients had a minimum survival time of 4 years and of these 48 were studied in search for histological characteristics that might explain the unexpectedly good prognosis. In only 8 of the 48 patients (17%) could the diagnosis of malignant glioma of high malignancy grade be verified at histopathological reexamination. All 8 were grade III tumors according to WHO and no primary glioblastomas were found. The explanation for the erroneous registration was either incorrect initial pathological diagnosis or incorrect registration. No common morphological features could be found among the correctly registered long-term survivors. Survival data on gliomas based on original histopathological diagnoses derived from information in population-based cancer registers should be cautiously interpreted. Reliable conclusions can only be drawn when such data are supplemented with clinical information and the histopathology is reviewed.