The Use of Fluorescence Hybridization to Confirm Gene Rearrangement in Fibrolamellar Hepatocellular Carcinoma: A Validation Study.

Objective: The objectives of this study are to define the specificity of the fusion transcript for the fibrolamellar subtype of hepatocellular carcinoma (FL-HCC) by testing a targeted sampling of other hepatic neoplasms/proliferations and extrahepatic neoplasms seen in children and young adults and to develop a FISH assay using a commercially available break apart probe for use in a CLIA-certified clinical laboratory.

Methods: Formalin fixed paraffin embedded tissue sections from 12 FL-HCC cases, 142 cases of other hepatic neoplasms/proliferations (conventional HCC, focal nodular hyperplasia (FNH), hepatocellular adenoma (HA) and hepatoblastoma (HB)) and extrahepatic neoplasms (neuroblastoma (NB), Wilms tumor (WT) and Gastrointestinal neuroendocrine tumor (GNET)) and 60 matched background normal control tissues underwent fluorescence in situ hybridization (FISH) testing using a break apart probe targeting the gene locus on chromosome 19 using standard techniques.

Results: The gene rearrangement was detected in 11/12 (92%) FL-HCC cases and 1/94 (1%) of conventional HCC cases. All other cases and background control tissues were negative for the gene rearrangement. These findings establish a test sensitivity of 91.7% and specificity of 99.5%.

Conclusion: This study shows that, using standard techniques, FISH testing with a commercially available break apart probe targeting the gene can be used as a surrogate for the fusion commonly found in FL-HCC. Also, the gene rearrangement is not expressed in other hepatic neo-plasms/proliferations or extrahepatic neoplasms seen in children and young adults. Finally, FISH testing can be used as a diagnostic tool to confirm the diagnosis of FL-HCC, in the appropriate clinical setting.