DNA cytofluorometric analysis of benign and malignant nerve sheath tumors

The present study was undertaken to examine the ploidy patterns of benign and malignant nerve sheath tumors using PI-DNA cytofluorometry and to clarify the relationship between the ploidy patterns and pathological findings for these lesions. The benign nerve sheath tumors (schwannomas and neurofibromas) were found to be dipolid or to be euploid-polyploidization, with a few DNA synthetic cells. The number of polyploid cells increased with increase in the frequency of cells with large and atypical nuclei in histology, regardless of the natures of cellular arrangements. Malignant schwannomas were composed of many polyploid and aneuploid cells with DNA synthetic cells, indicating their active cell proliferation. Thus, benign nerve sheath tumors exhibited low-proliferative ploidy patterns that were clearly different from those of malignant nerve sheath tumors. As Takeshita has already stated, it is difficult to ascertain why some of the neurogenic tumors show euploid-polyploidization (19). Further investigations will be needed in this direction. Finally, it is clear from the results of this study that the cytofluorometric analysis mentioned above is useful for assessing malignancy and that it may be useful for predicting prognosis of nerve sheath tumors.