A Unique Case of der(16)t(1;16) Identified in B-Lymphoblastic Leukemia

Abstract

Abstract Introduction/Objective A derivative chromosome 16 is rare in hematologic malignancies. There are only two previously reported cases to date, both associated with acute myeloid leukemia (AML). In these cases, the t(1;16) presented as a der(16)t(1;16) resulting in trisomy 1q. This was the sole anomaly in each case. Cytogenetic abnormalities in B-ALL are common and important for understanding of the pathogenesis, classification and prognosis of the disease. Herein we describe a case of der(16)t(1;16)(q12;q24) identified for the first time in a patient with B-cell acute lymphoblastic leukemia (B-ALL), with correlation with morphologic and immunophenotypic findings. Methods/Case Report The patient is a 65 year-old male who initially presented with one week of fatigue. A complete blood count showed leukocytosis (white blood cell count of 24.6 x 103/uL), anemia (hemoglobin of 7.9 g/dL), marked thrombocytopenia (platelets of 5 x 103/uL). A differential showed 64% blasts and peripheral blood flow cytometry confirmed B-lymphoblastic differentiation, with two distinct immunophenotypic populations. The patient’s bone marrow biopsy was hypercellular (>95% cellularity) with panhypoplasia and a marked increase in blasts (88% by aspirate manual differential). Cytogenetic analysis of the bone marrow also demonstrated the presence of two clonal cell lines. The first cell line was chromosomally normal, while the second had a t(9;22) translocation and a derived chromosomes 16 from a t(1;16). FISH analysis confirmed 59% of cells demonstrated a BCR/ABL1 fusion event. Results (if a Case Study enter NA) NA Conclusion The patient’s der(16)t(1;16)(q12;q24) represents a novel genetic abnormality that has not previously been reported in B-ALL. Although it has been described in other acute leukemias, little is known about this abnormality in B-ALL and its implications in pathogenesis and prognosis. Additional molecular testing, including chromosomal microarray analysis, mate-pair, or long-range DNA sequencing or RNA sequencing, could potentially identify the fusion partners and shed light on pathophysiological mechanisms implicated in the leukemic process.