Secondary acute myeloblastic leukemia with t(16;21)(q24;q22) involving the AML1 gene

A t(16;21)(q24;q22) translocation was detected by fluorescence in situ hybridization in a patient with acute myeloblastic leukemia previously treated for malignant lymphoma. While the breakpoint on chromosome 21 was within the AML1 gene as determined by FISH, the gene partner on chromosome 16 could not be identified. Band 16q24 appears to be rearranged in several types of myeloid proliferation and a review of the literature shows that these rearrangements most often occur in secondary leukemia and myelodysplastic syndrome or are part of complex chromosomal rearrangements.     

Acute myeloid leukemia with t(16;21)(q24;q22) in a child

The t(16;21)(q24;q22), a rare chromosomal translocation observed mostly in therapy-related acute myelogenous leukemia (AML), produces a RUNX1-CBFA2T3 fusion gene. Here we report a de novo AML case of 1-year-old girl with t(16;21)(q24;q22). In this case, we demonstrated the RUNX1-CBFA2T3 fusion gene and established quantitative RT-PCR for detecting minimal residual disease.     

Childhood acute myeloid leukemia with bone marrow eosinophilia caused by t(16;21)(q24;q22)

Acute myeloid leukemia with abnormal bone marrow eosinophilia (AML-M4Eo) is often reported in core binding factor (CBF) leukemia, with translocations such as inv(16)(p13q22), t(16;16)(p13;q22) or t(8;21)(q22;q22); however, it is rarely reported with t(16;21)(q24;q22), which produces the RUNX1-CBFA2T3 (AML1-MTG16) chimera. The similarity between this chimera and RUNX1-RUNXT1 (AML1-MTG8) by t(8;21)(q22;q22) remains controversial. Adult leukemia with t(16;21)(q24;q22) was primarily therapy related, and shows poor prognosis; however, pediatric AML with this translocation was quite rare and tended to be de novo AML. We present here a 4-year-old boy with de novo AML-M4Eo and t(16;21)(q24;q22). He received chemotherapy and survived for more than 70 months without transplantation. We speculated that pediatric AML with t(16;21)(q24;q22) showed favorable prognosis, as with t(8;21)(q22;q22).     

Distinctive immunophenotypic features of t(8;21)(q22;q22) acute myeloblastic leukemia in children.

Thirty cases of newly diagnosed pediatric acute myeloblastic leukemia (AML) with French-American-British (FAB) M2 morphology were analyzed with cytogenetics and a comprehensive panel of monoclonal antibodies reactive with lymphoid-, natural killer (NK)-cell-, and myeloid-associated antigens. The t(8;21)(q22;q22), or t(8;21;V)(q22;q22;V), translocation was identified in 16 of the 30 cases. Cases with the t(8;21) did not differ significantly from the remaining M2 cases with respect to expression of CD11b, CD13, CD14, CD15, CD33, CD34, CD36, CD41a, CD42b, CDw65, TdT, or HLA-DR. Expression of the B-cell antigen CD19 was detected in 13 of the 16 t(8;21) cases (81%), but in only 1 of the 14 (7%) other M2 cases (P = .00006). Expression of the CD56 NK-cell antigen was also significantly more frequent among t(8;21) cases (63% v 14%; P = .01). Coexpression of CD19 and CD56 was found only in the t(8;21) group (9 of 16 cases, P = .0009). Furthermore, this phenotype was not found in 48 evaluable cases of de novo AML of the FAB M1, M3, M4, M5, or M7 subtypes. The 14 M2 AML cases lacking the t(8;21) commonly expressed CD2 (n = 5) or CD7 (n = 8). However, no case with the t(8;21) expressed either antigen (P = .01 and .0005, respectively). Thus, the t(8;21) biologic subgroup of pediatric M2 AML has distinct immunophenotypic characteristics that distinguish it from other types of de novo AML.     

B-Lymphoid and myeloid lineages biphenotypic acute leukemia with t(8;21)(q22;q22)

By analyzing the characteristics of morphology, immune phenotype, chromosome karyotype and clinical manifestations of six cases of B-lymphoid and myeloid lineages biphenotypic acute leukemia (BAL) with t(8;21)(q22;q22), a new subgroup of BAL was reported. Bone marrow eosinophilia (more than 5%) and pseudo-Chediak abnormalities were not found. Auer rods were also not identified in four of six cases. Immunophenotype revealed B-lymphoid and myeloid lineages positive, together with frequent and high expression of CD34 and CD33, and weak expression of HLA-DR. In addition to t(8;21) chromosomal translocation, deletion of Y chromosome and complex chromosome abnormalities were also found. Chemotherapy for myeloid and lymphoid leukemia simultaneously produced good response in the patients. BAL with t(8; 21)(q22; q22) might be a new subgroup of BAL, and it was suggested that the leukemia clone with t(8;21)(q22;q22) might have originated from an early phase of hematopoiesis, and AML1/ETO fusion gene might be related to differentiation of B lymphocyte.