Feasibility and limitations of a cytometric DNA ploidy analysis procedure in tissue sections

To produce IOD histograms from tissue sections interpretable in terms of DNA ploidy, compromises between section thickness, nuclear volume and cellularity have to be found. In most cases, some kind of correction for capping effects will be inevitable. One of the correction procedures for that purpose was studied, i.e. that concerning the extent of errors which are necessarily introduced by assuming a distributional model of nuclei in the tissue slide. This procedure is mainly based on the assumptions of a spherical shape of the nuclei, of their homogeneous chromatin distribution, and of an equal distribution of the equatorial plane inside the tissue slide sectioned. Measurements on rat liver sections with a series of section thicknesses demonstrated that the correction procedure would lead to an exact position of the IOD peaks from the tetraploid nuclei on the ploidy axis. The width of the IOD peaks will not be diminished considerably as compared to uncorrected IOD histograms. Therefore, there are serious limitations to the procedure as compared to the DNA ploidy analysis on smears or imprints. If applied very critically in the case of tissue sections, the method may provide additional information about the DNA ploidy in those cases which lack a uniform tumour cell population or adequate material for smear preparations.