[Ultrastructural characteristics of nephroblastoma and its relation to DNA ploid]

Fifty-one cases of nephroblastoma were studied by light and electron microscopy as well as microspectrophotometry. Under light and electron microscope, the tumor appeared to be carcinosarcoma structurally, consisting of epithelial, sarcomatous and undifferentiated tumor cells. Their ultrastructural feature was similar to that of renal tubular epithelial cells and fibroblasts. It could be differentially diagnosed from renal mesoblastic tumors by electron microscopy when the tumor was chiefly composed of sarcomatous cells. Microspectrophotometer measurement showed an increased average nuclear DNA content (DI greater than 1.04), belonging to aneuploid tumor with polyploid cells, serving as one important feature of malignant tumors. In addition, the poorer the tumor differentiation the higher was the DNA content of the tumor cells, suggesting that the measurement of nuclear DNA of tumor cells may also help ascertain the degree of differentiation and malignancy of nephroblastomas.