Cellular deoxyribonucleic acid content of renal oncocytomas: flow cytometric analysis of paraffin-embedded tissues from eight tumors.

Formalin-fixed, paraffin-embedded tissues from eight renal oncocytomas were analyzed using a Coulter Epics V cell sorter. Samples were processed using Hedley's method modified by including centrifugation through sucrose, RNAse digestion, and propidium iodide staining. The nuclei were excited using 200 mw of laser power at 488 nm. The tissues were all from surgical specimens acquired between 1972 and 1983, and the neoplasms met stringent light and electron microscopic criteria for the diagnosis. Sixteen samples were analyzed from the eight tumors; the coefficients of variation on the interpretable G1 peaks ranged from 3.95 per cent to 7.62 per cent with a mean of 5.46 per cent. One of the tumors had been frozen and yielded uninterpretably wide peaks. Control samples of non-neoplastic kidney from six of the specimens had coefficients of variation in a similar range. All of the oncocytomas with acceptable histograms had single, sharp G1 peaks with no evidence of aneuploidy. Proliferative indices were calculated and ranged from 0.02 to 0.18 for the oncocytomas and from 0.01 to 0.03 for renal cortex. The mean of the ratios of proliferative indices between the oncocytomas and the corresponding renal cortical samples was 4.5. These data support the concept that renal oncocytomas are euploid neoplasms with significant growth rates and are consistent with their benign biologic behavior and propensity to grow locally to large size.