THE UTILITY OF INTERPHASE FLUORESCENCE IN SITU HYBRIDIZATION IN THE DIAGNOSIS OF LYMPHOMAS

Lymphomas are characterized by heterogeneous biology, pathologic features, and clinical outcome. They are classified based on the normal counterpart, or cell of origin, from which they arise. Because lymphocytes have physiologic immune functions that vary both by lineage and by stage of differentiation; the classification of lymphomas coming from these normal lymphoid populations is complex. Genomic instability is a feature of lymphomas due to aberrant alterations at genetic, epigenetic, transcriptional, protein, and dysregulated oncogenic signaling pathways. Detection of specific chromosomal abnormalities is essential in diagnosing of several lymphoproliferative disorders. Interphase FISH investigates cytogenetic alterations, the gold standard technique localizes fluorescent signals to specific interphase non-dividing cells. Translocations and rearrangements are the common chromosomal alterations of lymphomas involving proto-oncogenes and tumor suppressors. The common abnormalities include: t (11;14) (q13; q32) in mantle cell lymphoma and in some cases of plasma cell myeloma; t(14;18)(q32;q21) in follicular lymphoma; t(8;14)(q21;q32) in Burkitt lymphoma; t(11;18)(q21;q21) in MALT lymphoma; BCL6 rearrangement in Large B-cell Diffuse Lymphoma (LBCL); IRF4/DUSP22 rearrangement in LBCL; t(2;5)(p23;q35) NPM-ALK in T-cell lymphomas. Less commonly are deletions, trisomy 12 or partial trisomy 12q13 in Chronic Lymphocytic Leukaemia (CLL). The WHO has recently introduced a particular type of lymphoma morphologically similar to Burkitt Lymphoma but without t (8;14) (q24; q32): instead, the following entity is cytogenetically characterized by a peculiar pattern of an 11q aberration consisting of a gain in 11q23.2-23.3 followed by a telomeric loss in 11q24.1-qter. This study aims to standardize Interphase FISH for diagnosing lymphoma associated with immunophenotypic features, focusing our attention on particular cases showing interested genic abnormalities, such as 11q alterations and t (11;14) in Precursor T-Lymphoblastic Transformation of Mantle Cell Lymphoma. During this study, we have also performed ImmunoFISH, a method combining immunolabelling with fluorescent in situ hybridization (FISH) to simultaneously detect the nucleo-cytoplasmic distribution of proteins and specific nucleotide sequences within the chromosomes.