Comparison of DNA ploidy in routine fine needle aspiration biopsy samples and paraffin-embedded tissue samples

The nuclear DNA content was determined by flow cytometry (FCM) from unfixed fine needle aspiration (FNA) biopsy samples of 31 human tumors, and from the same tumors after their excision, fixation with formalin and embedding in paraffin. The ploidy of the histograms was the same in 29 (94%) of the 31 cases. The disagreement in two cases may be explained by clonal heterogeneity of the tumors. The DNA index of the aneuploid cases was identical in fresh and fixed samples. The coefficient of variation of the diploid peaks (P less than .001) and the mean percentage of S-phase cells (P = .06) were larger in the fixed samples. It is concluded that routine FNA biopsy is a practical and reliable method for collecting cells for FCM DNA ploidy determination.