Sources and nature of variation in DNA analysis of follicular thyroid adenoma.

We investigated the sources and nature of variation that may occur in the DNA analysis of thyroid adenomas from cytological and histological samples. Imprints and smears gave identical results. However, the nuclear area was higher in smears where the optical density of the nuclei was lower. In measuring imprints, the interactive selection of nuclei was preferred to the automatic, because the risk of measuring nuclear fragments or undesired objects was thus avoided. The reproducibility and the variation of the DNA measurements depended on the degree of observer training in quantitative pathology, the method of field selection, and the type of instrumentation. Biological variation in the spatial distribution of nuclei with different ploidy values in some adenomas seemed to hide the influence of section thickness on measurements. Our data seem to suggest that it is best to apply a constant section thickness and 5 micron sections seem acceptable.