Comparison of DNA and karyotype aneuploidy in malignant lymphomas. Tumors from 48 patients with non-Hodgkin's lymphoma were examined for flow cytometric DNA ploidy and chromosome constitution to determine the degree of concordance of these two methods. Histologically, there were 24 low-grade, 19 intermediate, and 5 high-grade lymphomas. Flow cytometry revealed an aneuploid cell population in 19% of the cases. The mean DNA index of the aneuploid tumors was 1.58 +/- 0.71. The frequency of DNA aneuploidy was only slightly higher (23%) in intermediate than in low-grade lymphomas (17%). None of the five high-grade lymphomas showed DNA aneuploidy. The chromosome study was successful in 81% of cases (39 of 48), and clonal chromosome abnormalities were observed in 92% of these (36 of 39). In most of the chromosomally abnormal clones the chromosome number was in the diploid range. Most tumors with pseudodiploid (46 chromosomes), hypodiploid (45-44 chromosomes), or hyperdiploid (47-49 chromosomes) clones were DNA diploid by flow cytometry. On the other hand, all specimens with a chromosome number exceeding 50 were DNA aneuploid by flow cytometry. Therefore, flow cytometric DNA analysis appears to be a rather coarse method that will detect aneuploidy only when there is a major increase in chromosome material. 