The BCL2 (BCL2, apoptosis regulator, a.k.a. PPP1R50) gene encodes a mitochondrial membrane protein that regulates apoptosis and is expressed in B-cells. Translocations involving the BCL2 gene are commonly identified in B-cell lymphomas. In particular, the translocation t(14;18) (q32.3;q21.3) has been identified in about 80% of follicular lymphoma (FL), in 20% to 30% of diffuse large B-cell lymphoma (DLBCL), and rarely in B-cell chronic lymphocytic leukemia (B-CLL). In FL this translocation is considered to be a cytogenetic hallmark. As a result of this rearrangement, the BCL2 gene is juxtaposed to IGH (Immunglobulin heavy locus) at 14q32.33 which leads to overexpression of the anti-apoptotic protein BCL2, and finally to progression to lymphoma. Alternative BCL2 translocations to immunoglobulin light chain genes as well as non-IG translocation events have been reported. In DLBCL, BCL2 gene overexpression has been implicated in conferring resistance to chemotherapy and has been associated with poor prognosis. Hence, detection of BCL2 translocations by Fluorescence in situ Hybridization (FISH) may be of diagnostic and prognostic relevance.