The purpose of this study was to investigate the roles of bcl-2 chromosomal translocation and Bcl-2 protein expression in follicular lymphoma (FL) minimal bone marrow (BM) infiltration. We identified the same bcl-2/IgH fusion gene in paraffin-embedded lymph node (LN) samples and BM samples using immunohistochemistry (IHC), immunocytochemistry (ICC), cytologic morphology and fluorescence in situ hybridization (FISH). The presence of the Bcl-2/IgH fusion gene in the BM samples and paraffin-embedded LN samples from 56 patients with follicular lymphomas was detected using FISH. The Bcl-2 protein levels in BM and paraffin-embedded tissues were quantified using ICC and IHC, respectively. Approximately 78.6% (44/56) of the paraffin‑embedded LN tissue sections that underwent FISH analysis had a bcl-2/IgH translocation. The primary lesion was also positive for the bcl-2/IgH fusion gene, as were the BM minimal infiltrates. The bcl-2/IgH rearrangement occurred in 88.6% (39/44) of the BM specimens. The bcl-2/IgH recombination rate in stage III/IV cancers was significantly different to that observed in stage I/II cancers (p=0.041). In 59% (23/39) of the cases with t(14;18), Bcl-2 was found to be present as assessed by ICC. Positive Bcl-2 ICC staining and the t(14;18) translocation (as detected using FISH) were positively correlated (p=0.028). We then applied the FISH method to slides that had previously been morphologically evaluated using Wright-Giemsa staining; any slides with at least one abnormal cell were subjected to FISH analysis following staining. The assessment of bcl-2/IgH translocation status may contribute to the better detection of minimal BM infiltration by FL cells. Utilizing FISH and cytologic morphology techniques allows for earlier and more accessible BM examination.

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