Flow cytometry in the diagnosis and classification of malignant lymphoma and leukemia

Abstract

DNA content and light scatter were measured by flow cytometry (FCM) in 103 patients including 43 patients with non-Hodgkin's lymphoma (NHL), eight patients with Hodgkin's disease (HD), 17 patients with acute lymphoblastic leukemia (ALL), ten patients with acute nonlymphocytic leukemia (ANLL), and 25 patients with chronic lymphoid leukemias. Controls consisted of 42 nonneoplastic specimens obtained from lymph nodes, spleen, bone marrow, and peripheral blood. Each specimen was analyzed after staining with a hypotonic solution of propidium iodide using nuclei isolated from chicken erythrocytes as an internal standard. The DNA content and light scatter of the human populations was expressed as a ratio between the DNA content (or light scatter) of the human G₀-G₁ cells and that of the chicken erythrocyte nuclei. The mean DNA ratio for the 42 nonneoplastic samples was 2.58 ± 0.045 (SD). In these samples the DNA coefficient of variation of the human G₀-G₁ peak ranged from 1.48–3.28% (mean, 2.33 ± 0.54%). The FCM data in the NHL was compared to morphologic diagnoses made according to the “working formulation of NHL for clinical usage” recently proposed by a panel of international experts. Eight of 17 (47%) low grade NHL, one of two (50%) mycosis fungoides, ten of 14 (71%) intermediate grade NHL, nine of ten (90%) high grade NHL, nine of 17 (53%) ALL, three of ten (30%) ANLL, and seven of 25 (28%) chronic lymphoid leukemias had abnormal DNA ratios indicative of aneuploidy. In addition, several cases had normal DNA ratios but G₀−G₁ coefficients of variation outside of the normal range. All cases of HD had normal DNA values except one case with a small percentage of near tetraploid cells. The mean percentage of cells with S-phase DNA content for the low grade NHL (2.2 ± 0.8%) was significantly lower than that of the intermediate grade NHL (12.1 ± 4.9%; P < 0.0001). The mean S-phase value for the intermediate grade NHL was significantly lower than that of the high grade NHL (22.6 ± 11.1%; P < 0.001). The three prognostic categories of NHL designated by the new formulation were clearly distinguishable by the FCM data. Light scatter was not particularly useful for distinguishing nonneoplastic from neoplastic populations. The mean light scatter coefficient of variation of the ALL (15.2%) was significantly lower than that of ANLL (20.5%), however (P < 0.04).