Childhood pre-B cell acute lymphoblastic leukemia with translocation t(1;19)(q21.1;p13.3) and two additional chromosomal aberrations involving chromosomes 1, 6, and 13: a case report

On 22 May 2014, a 15-year-old Syrian boy without significant personal or familial history of malignancies presented to Al-Biruni University Hospital with a 1-month history of bleeding gums, fatigue, and pallor. He had no familial history of malignancies and no social and environmental history or exposure to toxins and animals. A physical examination revealed splenomegaly without lymph node involvement. An initial laboratory evaluation of peripheral blood (PB) revealed elevated WBC count of 56×10⁹/l with 94% of blasts cells, anemia (9.1 g/dL), and a thrombocytopenia (123×10⁹/L). His serum LDH value was 862 U/l (normal value up to 480 U/l). He was diagnosed as having pre-B-ALL according to the World Health Organization (WHO) classification. A biopsy of his bone marrow (BM) revealed hypercellular marrow (WBC count 155.3×10⁹/l with 94% of blasts cells).

He was referred (on 25 May 2014) to our Chromosomes Laboratory and Flow-cytometry Laboratory, Molecular Biology and Biotechnology Department, Atomic Energy Commission of Syria, for cytogenetics and flow-cytometric analyses. He could be classified in a high risk group. Thus, he was supplied with German Multicenter Study Group for Adult Acute Lymphoblastic Leukemia (GMALL) protocol treatment after the initial diagnosis for 5 months. Unfortunately, due to the political situation in his home country he was given available drugs such as vincristine 1.4 mg/m², doxorubicin 25 mg/m², and methotrexate 20 mg/m². He responded to that treatment without any infiltrations in his BM; he received platelets and blood transfusions many times; his PB showed pancytopenia and neutropenia. The treatment was stopped before consolidation phase because his BM biopsy evaluation showed morphologic remission (8% blasts left); a cerebrospinal fluid test revealed abnormal cells; he also had a pulmonary infection. Approximately 5.5 months after initial diagnosis he died due to unknown causes while under treatment. No autopsy was performed because he died in his house. His parents agreed with the scientific evaluation of the case and a study was approved by the ethical committee of the Atomic Energy Commission, Damascus, Syria.

A chromosome analysis on a BM sample using GTG-banding according to standard procedures [10] was performed before his treatment started; it revealed a karyotype of 46,XY,del(6)(q?),der(13)t(1;13),der(19)t(1;19)[6]/46,XY,del(6)(q?),der(19)t(1;19)[5]/47,XY,+i(1)(q?),del(6)(q?),der(19)t(1;19)[1]/46,XY[6] (Fig. 1). Karyotype was described according to the International System for Human Cytogenetic Nomenclature (ISCN) of 2013 [11].

Further studies were performed on BM sample using molecular cytogenetics (Fig. 2). We performed dual-color fluorescence in situ hybridization (D-FISH) with specific whole chromosome paint (WCP) probes for chromosomes 1, 6, 13, and 19 (MetaSystems, Altlussheim, Germany) [10], which did not provide any information on the cryptic translocations (data not shown), and array-proven high-resolution multicolor banding (aMCB) [12], using probes for the corresponding chromosomes 1, 6, 13, and 19 involved according to GTG-banding (Fig. 2). Reverse transcriptase-polymerase chain reaction (RT-PCR) for E2A-PBX1 fusion transcripts was performed prior the treatment using specific primers previously described [13], confirmed the presence of the TCF3/PBX1 fusion (E2A/PBX1 transcript; 373-base pair band), most often identified in acute lymphoblastic leukemia (ALL; data not shown). Thus, the following final karyotype prior to treatment was determined using a fluorescence microscope (AxioImager.Z1 mot, Carl Zeiss Ltd, Hertfordshire, UK) equipped with appropriate filter sets to discriminate between a maximum of five fluorochromes plus the counterstain 4',6-diamidino-2-phenylindole (DAPI). Image capture and processing were performed using an ISIS imaging system (MetaSystems): 46,XY,del(6)(q12q26),der(13)t(1;13)(q21.1;p13),der(19)t(1;19)(q21.1;p13.3)[6]/46,XY,del(6)(q12q26),der(19)t(1;19)(q21.1;p13.3)[5]/47,XY,+i(1)(q10),del(6)(q12q26),der(19)t(1;19)(q21.1;p13.3)[1]/46,XY[6].

Immunophenotyping was performed on BM sample using a general panel of fluorescent antibodies against the following antigens typical for different cell lineages and cell types: CD1a, CD2, CD3, CD4, CD5, CD8, CD10, CD11b, CD11c, CD13, CD14, CD15, CD16, CD19, CD20, CD22, CD23, CD32, CD33, CD34, CD38, CD41a, CD45, CD56, CD57, CD64, CD103, CD117, CD123, CD138, CD209, CD235a, and CD243; in addition, antibodies to kappa and lambda light chains, IgD, surface-bound IgM (sIgM), and human leukocyte antigen-antigen D related (HLA-Dr) were tested. All antibodies were purchased from BD Biosciences (San Jose CA, USA). Samples were analyzed on a BD FACSCalibur™ flow cytometer. Autofluorescence, viability, and isotype controls were included. Flow cytometric data acquisition and analysis were conducted by BD Cellquest™ Pro software. Flow cytometric analysis of BM specimen characterized this case as pre-B-ALL according to WHO classifications. The abnormal cell population (94% of tested cells) was positive for CD45^+dim, CD19⁺, CD10⁺, HLA-DR⁺, and CD79a⁺. This cell population was negative for CD34, CD2, CD7, CD13, CD14, CD15, CD20, CD33, and CD117.