CAVEATS IN THE USE OF ARCHIVAL CELL MATERIAL FOR DNA-PLOIDY ANALYSIS BY IMAGE CYTOMETRY

Monolayer preparation from paraffin-embedded tissue from archival biop sy specimens older than 10 years was shown in this study to be more di fficult to deal with than recent biopsies. We have studied the dissemi native effect of several enzymes on archival biopsies from laryngeal e pithelium, as well as mechanical dissemination. Thirty minutes incubat ion in protease 0.5% in 37 degrees C without syringing provided the be st cell yield. Hydrolysis and Schiff staining conditions were also stu died. Cell loss was calculated by stereological methods and found to b e high in most cases. Cell loss during various steps in monolayer prod uction was examined and we found no proof of selective cell loss. Larg e variations in Feulgen-Schiff staining intensities were observed, esp ecially in biopsy specimens older than 10 years. The use of reliable i nternal (intrinsic) control cells is advocated since interspecimen var iations in the diploid integrated optical density (IOD) can be expecte d. Although DNA measurements on archival biopsy material should be tre ated with caution, we demonstrate that meticulous studies of the prepa ration procedures will make it possible to obtain reliable histograms from old, archival biopsies.