Investigation of bone marrow involvement in malignant lymphoma using fluorescence in situ hybridization: possible utility in the detection of micrometastasis.

We evaluated the usefulness of interphase fluorescence in situ hybridization (FISH) for the detection of bone marrow involvement of lymphoma, comparing the results with those of microscopic examination. Bone marrow aspirates obtained for staging work-up from 150 patients with non-Hodgkin lymphoma were used in this study. Interphase FISH study using four probes and conventional G-banding were performed on bone marrow aspirates. The four probes included locus specific identifier (LSI) immunoglobulin heavy chain (IGH) dual-color break-apart rearrangement probe, an LSI p16 SpectrumOrange/CEP 9 SpectrumGreen probe, an LSI BCL6 dual-color break-apart rearrangement probe. Among 150 cases, 29 cases (19.3%) showed infiltration of neoplastic lymphoid cells by microscopic examination. Chromosomal aberrations were detected by FISH in eight patients and by conventional cytogenetic study in three patients. FISH study showed 14q32 rearrangement in four patients (4/126, 3.2%), 9q21 rearrangement in no patients (0/144, 0%), 3q27 rearrangement in four patients (4/131. 3.1%), and a gain of 1q21q32 in two patients (2/115, 1.7%). Among eight patients with abnormal FISH patterns, six had normal karyotypes or no analyzable metaphase according to the conventional cytogenetic study. Seven patients with FISH abnormality showed bone marrow involvement of lymphoma by microscopic examination. One patient, who was defined as having no evidence of bone marrow involvement by microscopic examination, showed a 3q27 aberration in the FISH study. Although the number of patients with BM involvement that was detected by FISH was low, abnormal FISH patterns were detected in six patients who did not have abnormal karyotypes. Therefore, FISH analysis would be beneficial in cytogenetic diagnosis and follow-up study of minimal residual diseases, once the cytogenetic changes are detected at initial diagnosis.