Molecular Evaluation of t(14;18)(bcl-2/IgH) Translocation in Follicular Lymphoma at Diagnosis Using Paraffin-Embedded Tissue Sections

Abstract

OBJECTIVE: Follicular lymphoma (FL) is one of the most common lymphomas, and is characterized by t(14;18) (q32;q21) in more than 80% of patients. The aim of this study was to determine the rate of t(14;18) positivity based on the detection of mbr or mcr in paraffin-embedded tissue samples. METHODS: The study included 32 paraffin-embedded tissue samples collected from 32 consecutive FL patients that were diagnosed and followed-up at our hospital between 1999 and 2006. The MBR breakpoint was identified based on real-time PCR using a LightCycler v.2.0 t(14;18) Quantification Kit (MBR), multiplex PCR, and seminested PCR. To identify the mcr breakpoint, real-time PCR was performed using specific primers and the FastStart DNA Master SYBR Green I Kit. To detect t(14;18) via fluorescence in situ hybridization (FISH) nuclei from paraffin-embedded tissue sections were extracted and used together with LSI IgH (immunoglobulin heavy chain) (spectrum green)/bcl-2 (B-cell leukemia-lymphoma 2) (spectrum orange) probes. RESULTS: The DNA and nuclei isolation success rate for B5 formalin-fixed, paraffin-embedded tissue sections (n = 12) was 42% and 33%, respectively, versus 95% and 60%, respectively, for 20 tissue sections fixed in formalin only. In all, 24 paraffin-embedded tissue sections were analyzed and mbr positivity was observed in the DNA of 82.14% via seminested PCR, in 53.57% via multiplex PCR, and in 28.57% via real-time PCR. We did not detect mcr rearrangement in any of the samples. In all, 15 of 16 patients (93.75%) whose nuclei were successfully isolated were observed to be t(14;18) positive via the FISH method. CONCLUSION: Semi-nested PCR and FISH facilitated the genetic characterization of FL tumors. As such, FISH and PCR complement each other and are both essential for detecting t(14;18) translocation.

Keywords

• follicular lymphoma
• fish
• multiplex pcr
• semi-nested pcr