Analysis of non-Hodgkin's lymphoma by conventional cytogenetics and fluorescence in-situ hybridisation.

Cytogenetic analysis was performed on 40 non-Hodgkin's lymphoma (NHQ node biopsies. Chromosomes X, 3 and 12 were the most frequently gained; of the much rarer monosomies, loss of chromosome 13 was most common. Structural abnormalities primarily involved chromosomes 14,1,18,6 and 17. A markedly greater number of chromosome gains were associated with low-grade disease when compared to high-grade. In order to obtain further information from the cytogenetic analysis of the NHL karyotypes, the fluorescence in-situ hybridisation (FISH) technique was applied to the series. The activation state of additional X-chromosomes was examined and evidence that more than one X-chromosome was present in the active state in 4/9 cases was obtained. Further, in an apparent case of monosomy X, a marker was identified as an abnormal X-chromosome by chromosome painting. Interphase FISH was applied to NHL cells and numerical chromosome changes were identified; this approach was also attempted on aged bone marrow smears from acute lymphocytic leukaemia patients, in order to test the utility of the technique on archival material. Dual chromosome painting was used to elucidate the origins of add(14) chromosomes in 8 of the cases. In the control and two other cases the translocated material was demonstrated to be from chromosome 18, in two cases it was from chromosome 3 and in one case them was an insertion of chromosome 11 material. it was not possible to identify the origins of the translocated material in one NHL and in the final case the apparent add(14) was demonstrated not to contain chromosome 14 material. Structural abnormalities of chromosome 6 were investigated both by chromosome painting and by hybridisation of the MYB gene. The latter, which was initially mapped to 6q23 before hybridisation to NHL cells revealed previously unsuspected rearrangements. One case contained extrachromosomal chromatin bodies that appeared to be double minute chromosomes (dmin), which FISH analysis demonstrated to be derived from the X-chromosome and contain centromere-associated DNA. The significance of these results is discussed with reference to previously published series of NHL karyotypes