A consideration on histopathologic variability of diffuse pleural mesothelioma based on DNA cytophotometry

Nuclear DNA cytophotometry of the tumor cells was performed for an autopsy case of malignant diffuse pleural mesothelioma diagnosed histologically as a mixed type. The DNA distribution of these tumor cells confirmed bimodality, one being situated in the triploid and the other in the pentaploid DNA range, thus indicating two stemline cell populations. In the former, the majority were epithelial mesothelioma cells resembling the normal mesothelial cells. The latter were mesenchymal tumor cells with spindle and occasionally bizarre shaped nuclei. This cytophotometric data strongly suggests that the histologic variability in mesotheliomas results probably from the change in number and ploidy level of the stemline cell population accompanied by neoplastic development.