[Malignancy grading of glial tumors. II. Oligodendrogliomas]

Surgical biopsy material from 55 oligodendrogliomas was classified according to a four-level system of malignancy grading. Categorization was based on following criteria: numerical cell-density, cell and nuclear polymorphism, mitotic activity, proliferative activity of the vascular elements and degenerative phenomena, in particular necrosis. According to the intensity of these features, tumors were assigned to a malignancy level. The number of tumors alloted to each of the four ascending levels were 7, 15, 19, and 14, respectively with corresponding median survival times of 61.7, 27.7, 19.5, and 7.4 months. There was no statistically significant difference in the duration of survival between levels 2 and 3. The results of the investigation are consistent with reports from the literature which identify three prognostic grades for oligodendrogliomas, namely a group with low malignancy and a relatively good prognosis, an intermediate group and a group with a high level of malignancy and an extremely poor prognosis. It is suggested that the use of automated microscope image analysis or other quantitative methods contribute to more objective and reliable results.