DNA CONTENT MEASUREMENT CAN BE OBTAINED USING ARCHIVAL MATERIAL FOR DNA FLOW-CYTOMETRY - A COMPARISON WITH CYTOGENETIC ANALYSIS IN 56 PEDIATRIC SOLID TUMORS

Background. Although flow cytometry (FCM) has become a widely used tec hnique for the measurement of DNA content in solid tumors, the correla tion of ploidy analysis by FCM with cytogenetic analysis (CGA) is not well described. The sensitivities of G-banded CGA and FCM were compare d to determine the accuracy of the DNA index value (DI) as a measureme nt of chromosome number. Methods. Tumor specimens from 56 pediatric ca ses were analyzed for DNA content by both FCM and CGA. Nuclei for FCM were prepared from archival tissue in 53 specimens using a modificatio n of the Hedley technique and from fresh tissue in 3 specimens. Metaph ase chromosomes for CGA were prepared from standard solid tumor harves ts and Giemsa-trypsin banding procedures. Ploidy status for this study was defined as (1) diploid-DI between 0.97 and 1.03 by FCM or chromos ome number + 2 from normal by CGA (44-48); and (2) aneuploid-DI < 0.97 or > 1.03 by FCM or total chromosomes < 44 or > 48 by CGA. Results. F orty-nine of the 56 pediatric specimens were evaluable by both techniq ues. Concordance was observed in 34 cases (69%) between the two techni ques in assigning similar ploidy status to a tumor (22 diploid and 12 aneuploid). It also was observed that among the aneuploid concordant c ases, the actual DI obtained from archival material could predict tota l chromosome number with 95% accuracy. The 15 discordant cases showed a distinct aneuploid population by FCM, but were diploid by CGA. Concl usions. A correlation of 69% was obtained between both techniques to a ssign a similar ploidy status (diploid versus aneuploid) in 56 pediatr ic solid tumors. These results support the combined use of CGA and FCM to obtain the most complete analysis of DNA content and chromosome ab normalities in pediatric solid tumors. FCM on formalin-fixed, paraffin -embedded tissue can be used to measure total DNA content.