Different opinions on classification of DNA histograms produced from paraffin-embedded tissue

Flow cytometric DNA ploidy determination has been regarded as an objective prognostic parameter in several types of human cancer. To test whether DNA histograms are similarly interpreted, a series of flow cytometric DNA histograms was posted to six investigators working in the field for independent classification. The histograms were produced from paraffin-embedded adrenal adenomas or non-neoplastic tissue and had several different patterns. Only 44% of the histograms were similarly classified by all investigators, and 85% by five of the six participants, when DNA ploidy was evaluated. Different criteria for tetraploidy existed, and also some uncertainty in classifying peridiploid and small aneuploid peaks. It is concluded that lack of consensus on histogram classification may result in widely varying percentages of DNA aneuploid tumors found even if the data are similar. Until general agreement is reached on the definition of DNA aneuploidy and its subclasses, classification of DNA histograms is variable and subjective.