Detection of ploidy in colorectal tumors. A comparison between flow cytometry and cytogenetics.

Parallel investigations of ploidy by flow cytometry and cytogenetics were performed in 20 colorectal tumors. Flow cytometry detected an aneuploidy in 13 tumors with DNA indices ranging from 1.13 to 2.21. The other samples exhibited an apparent diploid DNA content. Cytogenetic analyses revealed an abnormal chromosome count in 14 cases and a frequent implication of numerical or structural changes in chromosomes 1, 7, 12, 17, 18, and 20. DNA content evaluated by both techniques was generally concordant with minor discrepancies not exceeding 10%. In six cases, cytogenetics failed to find the cell populations detected by flow cytometry. These results indicate that flow cytometry and cytogenetics are reliable and complementary techniques, particularly in near-diploid tumors, where flow cytometry has some difficulties in detecting variations from diploidy below to 8%.