Three adults with acute lymphoblastic leukemia and dic(7;9)(p11.2;p11)

A Retrospective Observational Study of Dicentric (9;12): A Unique, Nonrandom Translocation Defining a Cytogenetic Subgroup with Favorable Outcome in Acute Lymphoblastic Leukemia

Introduction Cytogenetic abnormalities are integral to the risk stratification of acute lymphoblastic leukemia (ALL).

Objectives The present study aimed to highlight a rare, yet nonrandom cytogenetic abnormality notably dicentric (9;12), which was observed in ALL patients who presented to our institute. The study analyzed the frequency, clinicohematological features, and treatment response of these patients.

Materials and Methods A single-group observational study was conducted from April 2014 to April 2020. Cytogenetic analysis was done on bone marrow aspirate samples of the patients referred to the cytogenetics laboratory with clinical diagnosis of acute leukemia. Cytogenetic, clinical, and hematological data were collected from respective departmental records, case files, and patients.

Results Dic(9;12) was identified in 1.2% of ALL (19 out of 1,544 patients). They showed striking preponderance in teen and young adult males with characteristic precursor B cell immunophenotype. Majority of these patients displayed favorable risk profiles such as low total count, mild lymphadenopathy and splenomegaly, mild-to-moderate elevation of lactate dehydrogenase, and good response to first induction chemotherapy. Rare coexistence of dic(9;12) with well-established cytogenetic markers such as t(9;22) and t(1;19) was observed.

Conclusion Dic(9;12) is one of the most specific cytogenetic markers of precursor B cell (pre-B) ALL. It defines a subgroup with favorable clinical and biological profile. We suggest inclusion of dic(9;12) in cytogenetic risk stratification of precursor B cell ALL. Long-term follow-up studies are recommended to establish the prognostic significance of this cytogenetic subgroup, which may benefit from less intensive chemotherapy.

Adult B-cell acute lymphoblastic leukemia with two unrelated abnormal cytogenetic clones

The presence of two different abnormal cell lines at diagnosis in hematologic malignancies is rare and raises the question of etiology and pathogenesis--two separate malignant lineages occurring together or a common stem cell malignancy? We present a 64-year-old woman who was evaluated for low platelet count and peripheral blasts. On the basis of the morphology, flow cytometry, and lack of myeloid-associated markers, a diagnosis of precursor B-cell acute lymphoblastic leukemia (B-ALL) was made. Cytogenetic analysis of the diagnostic bone marrow (BM) specimen revealed two unrelated abnormal clones--one had a dicentric (7;9)(p11;p11), resulting in the deletion of 7p and 9p, and the other had only trisomy 8. The dic(7;9) is a rare but recurrent abnormality in B-ALL, while trisomy 8 as a sole abnormality is most commonly associated with myeloid malignancies. After standard treatment for B-ALL, BM cytogenetic analysis showed disappearance of the dic(7;9) cell line but persistence of cells with trisomy 8. The presence of two unrelated clones suggestive of concomitant malignancies, possibly B-ALL with an underlying MDS, may have arisen by different mechanisms.

Tiling resolution array CGH of dic(7;9)(p11∼13;p11∼13) in B-cell precursor acute lymphoblastic leukemia reveals clustered breakpoints at 7p11.2∼12.1 and 9p13.1

The dic(7;9)(p11 approximately 13;p11 approximately 13) is a recurrent chromosomal abnormality in acute lymphoblastic leukemia (ALL), mainly of B-lineage. Although more than 20 dic(7;9)-positive ALLs have been reported to date, the molecular genetic consequences of this aberration are unknown. We performed tiling resolution (32K) genome-wide array-based comparative genomic hybridization (array CGH) analysis of three cases with dic(7;9) in order to characterize the breakpoints on 7p and 9p. The analysis showed a clustering of breakpoints within 9p13.1 in all three cases and within 7p11.2 in two cases; the array CGH revealed two different breakpoints - 7p12.1 and 7p14.1 - in the remaining case. Based on these findings the abnormality should hence be designated dic(7;9)(p11.2 approximately 12.1;p13.1). Locus-specific fluorescence in situhybridization analysis of one of the cases narrowed down the 7p11.2 breakpoint to a <500-kb segment in this sub-band, a region containing three known genes. Unfortunately, lack of material precluded further molecular genetic studies, and it thus remains unknown whether the pathogenetically important outcome of the dic(7;9) is formation of a chimeric gene or loss of 7p and/or 9p material.