Fluorescence in situ hybridization (FISH) for the detection of t(14;18)(q32;q21) involving IGH and MALT1 on metaphase chromosomes and interphase nuclei of a hepatic MALT lymphoma.

(A) The dual break-apart probe for IGH confirmed the rearrangement of the IGH locus showing the red signal on the der(14) and the green signal on the der(18), whereas the normal chromosome 14 carries the colocalization signal. By using probes forIGH and BCL2 (B), a split green signal forIGH is seen on der(14) and der(18), confirming the IGH translocation, however, the red signal for BCL2 is observed only on the der(14), indicating that the breakpoint is centromeric toBCL2. Moreover, the interphase nucleus does not showIGH/BCL2 fusion signals. The translocation ofMALT1 is demonstrated in (C), featuring a split signal for the red MALT1 probe in the aberrant metaphase on the der(14) and der(18) and fusion signals in both the metaphase and interphase. The interphase FISH assay schematically shown in (D) usesIGH and MALT1 probes for the detection of the t(14;18)(q32;q21) in isolated nuclei of routinely processed tissue.