Derivative (3)t(3;18)(q27;q21)t(18;16)(q21;?) involving the BCL2 and BCL6 genes in follicular lymphoma with t(3;14;18)(q27;q32;q21).

Follicular lymphoma (FL) is genetically characterized by t(14;18)(q32;q21) involving the BCL2 gene (BCL2), and is often associated with 3q27 translocations involving the BCL6 gene (BCL6). We describe here an unusual case of FL with a variant three-way translocation t(3;14;18)(q27;q32;q21). A 57-year-old man was given a diagnosis of FL, grade 2. Chromosome analysis showed 49,XY,+X,+3,t(3;14;18)(q27;q32;q21),i(6)(p10),+21. Spectral karyotyping confirmed three derivative chromosomes, der(3)t(3;18)(q27;q21), der(14)t(3;14)(q27;q32), and der(18)t(14;18)(q32;q21). Furthermore, an extra chromosome 3 was shown to be an unbalanced translocation der(3)t(3;16)(q27;?). Fluorescence in situ hybridization (FISH) analyses detected an IGH/BCL2 fusion signal on the der(18)t(14;18)(q32;q21). FISH also demonstrated split signals of BCL2 and BCL6 on both the der(3)t(3;16)(q27;?) and the der(3)t(3;18)(q27;q21). The findings indicate that the three-way translocation involved BCL2, IGH, and BCL6 and that the der(3)t(3;16)(q27;?) contained the 18q21 fragment including BCL2. It is probable that the translocation between chromosome 16 and the der(3)t(3;18)(q27;q21) occurred after duplication of the der(3)t(3;18)(q27;q21) as clonal evolution. Thus, this additional chromosome was revised as der(3)t(3;18)(q27;q21)t(18;16)(q21;?) and the final karyotype was as follows: 49,XY,+X,t(3;14;18)(q27;q32;q21),+der(3)t(3;18)(q27;q21)t(18;16)(q21;?),i(6)(p10),+21. These findings suggest that the der(3)t(3;18)(q27;q21) involving BCL2 and BCL6 had a crucial role in the pathogenesis of FL with t(3;14;18)(q27;q32;q21).