A t(17;19)(q22;p13.3) Involving TCF3, a t(1;9)(p13;p13), and a 5' IGH Deletion in a Case of Adult B-cell Acute Lymphoblastic Leukemia.

TCF3 (19p13.3) abnormalities are relatively common in B-cell acute lymphoblastic leukemia (B-ALL). The t(1;19)(q23;p13) involving PBX1 is the most common of these rearrangements. The t(17;19)(q22;p13.3), resulting in the TCF3-HLF fusion gene, is also seen in B-ALL and is associated with an extremely poor prognosis. Herein, we present the case of a 25-year-old male diagnosed with B-ALL whose initial karyotype showed a t(17;19)(q22p13.3). FISH confirmed TCF3 involvement and also revealed a 5' IGH deletion. After treatment, the patient relapsed, at which point conventional cytogenetic studies showed a t(17;19), loss of the 5' IGH region, and a t(3;10) not seen in initial studies. After hematopoietic stem cell transplantation, the patient relapsed again, at which point conventional cytogenetic studies showed a complex karyotype with t(17;19), t(1;9)(p13;p13), and structural anomalies involving chromosomes 5, 7, and 14, but no IGH abnormalities by FISH. The t(1;9) has been shown to involve PAX5, which plays numerous regulatory roles in B-cell differentiation. Other PAX5 rearrangements have been detected in B-ALL cases of young adults and adolescents, but with unclear clinical significance. To the best of our knowledge, this is the first reported case of t(17;19)-ALL with concomitant 5' IGH deletion and t(1;9)(p13;p13) potentially involving PAX5, albeit at different time points in disease progression. This case provides insight into the clonal evolution of t(17;19)-ALL and the potential involvement of PAX5 and IGH aberrations in the evolution of this malignancy.