Follicular Lymphomas: Molecular Diagnosis of t(14;18)(q32;q21) –Fluorescence in situ Hybridization, Qualitative and Quantitative PCR

Overview

Diagnosis of follicular lymphoma (FL) is based on histology and immunohistochemical profile(CD20+, CD79alfa+, CD10+, BCL-2+, CD5-). A chromosomal marker – translocation t(14;18)(q32;q21)supporting the tumor diagnosis and useful for monitoring bone marrow or peripheral bloodinfiltration by the tumor cells is also used. The BCL2 gene (18q21) is controlled by an enhancer ofthe IGH gene (14q32) resulting in BCL-2 protein overexpression. The translocation is present inthe majority of patients with FL. The aim of the study was to introduce the quantitative PCR(RQ-PCR, real-time quantification) method for the assessment of the quantity of cells bearing thetranslocation t(14;18) in patients with FL. The fluorescence in situ hybridization on interphasicnuclei (I-FISH) in histologic sections was used for screening of patients with the t(14;18). A searchfor the break of the BCL2 gene at the major breakpoint region (mbr) was performed by means ofqualitative PCR. We determined the relative number of the tumor cells bearing t(14;18) translocation(mbr) in patients with FL by the RQ-PCR. The relative quantity of these cells was significantlyhigher in the lymph nodes than in the bone marrow or peripheral blood. The RQ-PCR is a toolof choice to monitor the activity of the disease in individual patients, and to detect an earlydisease relapse before its manifestation at the level diagnosed by morphology.

Key words:
follicular lymphoma – translocation t(14;18) – I-FISH – qualitative PCR – quantitativeRQ-PCR – minimal residual disease