DNA-flow fluorescence--cytometry of ependymomas. Report on ten surgically removed tumours

The distribution of DNA is estimated from flow cytometric histograms in surgical specimens of ten ependymomas of different location and varying anaplasia. In three cerebral tumours grade I--II, including one ependymoma of the 4th ventricle, only limited elevation of the 4 C maxima was a prominent feature, corresponding to the microscopical frequency of typical mitoses. Four grade-III ependymomas showed aneuploid or polyploid histograms with stem lines. One frontal tumour was classified as "transitional" because of more numerous mitoses and abnormally elevated S and G2 + M phases, which increased in tissue culture. A correlation between the degree of anaplasia with the DNA pattern was difficult to pursue in two spinal ependymomas obviously lacking microscopical mitoses: Both--one a so-called tanycytic variant of grade I--II, and the other probably a metastasis from a cerebellar tumour--had a clear polyploid DNA histogram with a strikingly increased proliferation index, similar to the more malignant tumours of grade III. Also flow DNA measurements probably allow the decoding of heterogenous mixtures of tumour cells which are not always benign in ependymomas of lower grades of anaplasia microscopically.