Detection of chromosomal translocations involving ALK gene in anaplastic large cell lymphoma by fluorescence in-situ hybridization and its clinical significance

Abstract

To investigate clinicopathologic features and clinical value of the chromosomal translocation involving anaplastic lymphoma kinase (ALK) in anaplastic large cell lymphoma (ALCL) by fluorescence in situ hybridization (FISH). A total of 55 cases, including 45 cases of ALCL and 10 reactive lymphoid hyperplasia, were collected during 1999 to 2006 in the Department of Pathology, Fudan University Shanghai Cancer Center, and Xinhua Hospital Affiliated to Shanghai Jiaotong University. All cases were studied by FISH using dual color break apart probes of ALK for detection of chromosomal translocation, compared with the previous results of immunohistochemistry (IHC) and reverse-transcriptase polymerase chain reaction (RT-PCR) for the detection of ALK aberrations. The result of FISH showed that the clear red and green fluorescence signals were detected in 38 cases of ALCL, in which conspicuous split signals were observed in tumor cells in 24 cases (63.2%), suggesting the rearrangement of the ALK locus, with multiple copies of ALK gene in one case. In addition, the rearrangement of the ALK locus was not identified in 14 of 38 cases (36.8%); and the FISH results were unable to be evaluated in 7 cases, because no fluorescent signals involving ALK gene were found or signals were too weak to be analyzed. The concordance for the detection ALK aberrations in ALCL between FISH and RT-PCR, FISH and IHC were both statistically significant (P < 0.01). Chromosomal translocation involving ALK gene was not found in all 10 cases of reactive lymphoid hyperplasia. ALCL is an entity of lymphoma characterized by special clinical presentation, morphology, and ALK aberrations. FISH is helpful for detection of the chromosomal translocations involving ALK in ALCL, however, the detection efficiency by FISH may be affected by storage time of the paraffin-embedded tissue; and therefore combined detection with IHC and RT-PCR could complement each other and help for differential diagnosis of ALK(+)ALCL from ALK(-)ALCL.