[Flow cytometric and karyotypic studies on meningiomas]

Although meningiomas have been regarded as one of the benign brain tumors, cases showing clinically malignant behavior have been reported. For the purpose of detecting the possibility of predicting different biological behavior in meningiomas, eleven meningiomas were studied with the aid of flow cytometric (FMC) and cytogenetic techniques. Morphologically two cases were diagnosed as syncytial meningiomas and nine as transitional meningiomas. The former included one case (#5) of "syncytial poorly structured meningioma" (Zang et al.). In the FCM study seven out of eleven cases showed diploid (2C) or near diploid modal peaks with small amounts of tetraploid DNA (4C) cells. The remaining four cases had larger cell populations at 4C. Cytogenetically cells corresponding to 2C and near 2C peaks were also proved to be composed of diploid or hypodiploid cells in all of the eight cases studied. Chromosomal analyses revealed normal karyotypes in three. The remaining five hypodiploid cases had common chromosomal aberrations in G22, including missing chromosome 22 in four cases and 22 q-deletion in one. Nine cases grown in culture were also studied by FCM and were able to be maintained in culture from 14 days to 5 months. Close to the terminal stage of culture, most of the cases in culture tended to have higher cell population at 4C and the appearance of cells even at 8C (polyploidization). Similar changes were also obtained in cultured human fibroblast and seem not to be specific to this benign tumor. These results are discussed with reference to the previous reports from the point of view of patterns of FCM histograms from surgical specimens, degree of hypodiploidy, morphological behavior. Further studies, especially relating to basic cell kinetics are needed before clinical application can be made.