Comparison of DNA content in non-Hodgkinʹs lymphoma as measured by flow cytometry and cytogenetics

Specific cytogenetic changes such as t(14;18) and t(8;14) are associated with specific histologic subtypes of non-Hodgkinʹs lymphoma (NHL) and may predict disease outcome. Nonspecific cytogenetic changes include other structural rearrangements or numerical changes such as monosomies and trisomies, which may cause changes in total cellular DNA content. In many solid tumors, the presence of abnormal DNA content may be predictive of clinical behavior. NHL biopsies, however, contain normal (diploid) as well as abnormal cells, and DNA changes in the peridiploid range are detectable by cytogenetic analysis, but not consistently by flow cytometry. In the present study, we performed flow cytometric and cytogenetic analysis of DNA on biopsies from 129 patients with non-Hodgkinʹs lymphoma (NHL). Cytogenetic studies were successful on 88 (68%) of the samples. There was 55% concordance between flow cytometric and cytogenetic techniques in detecting aneuploid DNA content, with the majority of discrepancies occurring in the peridiploid range. We also detected six samples which were aneuploid by flow cytometry, but diploid by cytogenetics. We suggest that a reasonable approach to determine DNA content, as it relates to prediction of outcome in NHL, would be to combine data from both of these techniques and analyze the results in terms of ranges of DNA rather than by categorizing as diploid versus aneuploid.