Flow cytometric measurement of DNA content in human solid tumors: A comparison with cytogenetics

The aims of this study were: (1) to test the accuracy of flow cytometry (FC) in the measurement of DNA content in human solid tumors, (2) to correlate the FC DNA-index (DI) with the chromosome modal number (CMN) provided by cytogenetic analysis (CG), and (3) to investigate the most frequent pitfalls in FC histograms classification. FC and CG analyses were performed in parallel on 113 samples of human solid tumors of different origin. FC provided an evaluable histogram in 110 out of 113 cases (97%), whereas a successful CG culture was obtained in 79 out of 113 samples (72%). In the 79 cases evaluable by both FC and CG, a concordant ploidy status was found in 66 cases (84%) (47 diploid and 19 aneuploid) (P < 0.001, chi-square test). In the 19 concordant aneuploid tumors a close correlation between the CMN and the DI was found (y = 0.019 x + 0.151; r = 0.860). Concerning the 13 discordant cases, 11 (85%) were classified as aneuploid by FC and as diploid by CG, while 2 cases (15%) were CG aneuploid (1 near-diploid and 1 tetraploid) and FC diploid. The current study suggests that FC is a reliable method for the measurement of tumor DNA content of the studied solid tumors. Special attention should be paid to the improvement of DNA histograms quality, in order to reduce the difficulties in the detection of near-diploid and near-tetraploid cell populations. Multiple sampling should be warranted whenever possible.