POLYSOMY OF CHROMOSOME-12 IN 60 PATIENTS WITH NON-HODGKINS-LYMPHOMA ASSESSED BY FLUORESCENCE IN-SITU HYBRIDIZATION - DIFFERENCES BETWEEN FOLLICULAR AND DIFFUSE LARGE-CELL LYMPHOMA

Sixty consecutive evaluable specimens from patients with non-Hodgkin's lymphoma (NHL) were studied for the incidence of polysomy of chromoso me 12 by fluorescence in situ hybridization (FISH) with probes for the repetitive DNA sequence in the centromeric region of chromosome 12. T hirty-six samples were from follicular lymphomas (FLs), and twenty-fou r were from diffuse large cell lymphomas (DLCLs). Fifty-two specimens (86%) were obtained by fine-needle aspiration of a diseased node, seve n (11.6%) were from involved bone marrows, and one specimen was from a pleural effusion. Twelve of the thirty-six (33%) cases with FL had tr isomy 12 in 3-41% of the cells (median, 10%) (normal controls had thre e signals in 1.4 +/- 0.7% of cells). Trisomy 12 was found in 62% of th e patients who had had FL for more than 5 years. Nine of the twenty-fo ur cases (37%) with DLCL had more than two copies of chromosome 12 in 4-92% of the cells (median, 78%), and all nine cases were of B-cell ph enotype. Unlike FL cells, some DLCL cells had 4-6 copies of chromosome 12. In previously untreated patients, 54% of DLCLs and 26% of FLs had subpopulations of cells containing more than two copies of chromosome 12 (P = 0.04). Only 2/7 cases of DLCL with polysomy 12 had rearrangem ent of the BCL2 gene, indicating that the majority of DLCL cases with polysomy 12 did not result from histologic transformation of low grade follicular lymphomas. These data demonstrate that FISH of interphase cells is a sensitive method for detecting numerical abnormalities of c hromosome 12 in NHL. The differences between FL and DLCL in the number of chromosomes 12 and the number of involved cells may be related to differences in the biology of these tumors. (C) 1994 Wiley-Liss, Inc.