The use of interphase fluorescence in situ hybridization for cytogenetic analysis on paraffin sections in children with non-Hodgkin lymphomas

Abstract

Background. According to WHO classification, the detection of genetic alterations in tumor cells enables definition of
the subtype of lymphoma more precisely. The FISH technique allows analysis of cytogenetic changes in the cells in any
phase of the cell cycle. The aim of this work was to develop the method of cytogenetic analysis with the use of FISH
on interphase nuclei extracted from paraffin-embedded sections, in cases of children with non-Hodgkin lymphomas.

Material and methods. The study population was 38 children with non-Hodgkin lymphoma aged from 1 to 16 years
(median age 8.3), diagnosed between 1993 and 2000. We tested paraffin-embedded malignant tissues. In the first stage of the work we developed the method of nuclei extraction from paraffin sections, then in the second stage we used it with FISH analysis in material from 28 children.

Results. We devised the optimal patterns of nuclei extraction from paraffin sections. FISH performed on the extracted interphase nuclei were positive in 36/40 (90%) of tested specimens of 24/28 patients (85.7%). We detected the cytogenetic changes in 11/28 patients (39.3%): in 6/17 cases of B-cell lymphoma, 2/5 lymphoblastic lymphoma and 3/6 anaplastic large cell lymphoma.

Conclusions. FISH analysis performed on paraffin-embedded tissues is, due to different reasons, difficult to evaluate. The introduction of interphase nuclei extraction method allows the increase in the detection of cytogenetic alterations by FISH in archival biopsed material. However, this technique requires an efficient fixation procedure. To define the significance of cytogenetic aberrations in pediatric lymphomas, further studies of large series of patients with long follow-up should be undertaken.