Susan Mathew

Reassessment of the prognostic significance of hypodiploidy in pediatric patients with acute lymphoblastic leukemia

The purpose of the current study was to evaluate the cytogenetic features of the hypodiploid leukemic cells of pediatric patients with this rare subgroup of acute lymphoblastic leukemia (ALL). In addition, the authors determined whether subdivision of the hypodiploid category served a prognostic purpose for these patients.

Novel cryptic, complex rearrangements involving ETV6-CBFA2 (TEL-AML1) genes identified by fluorescence in situ hybridization in pediatric patients with acute lymphoblastic leukemia.

In childhood B‐lineage acute lymphoblastic leukemia (ALL), the most common genetic change, the ETV6‐CBFA2 (TEL‐AML1) fusion resulting from the cryptic t(12;21)(p13;q22) is associated with a favorable outcome. Therefore, it is important to identify patients with this translocation so that they can receive appropriate treatment. To identify new partner breakpoints for ETV6 and CBFA2, we selected 30 patients with childhood ALL in whose leukemic cells a t(12;21) had been detected by RT‐PCR. Conventional cytogenetics revealed that 12p abnormalities were present in 10 patients and that other random abnormalities were present in another 15, including 9 with a numerical or structural abnormality of chromosome 21. Normal karyotypes were observed in the leukemic blasts of five patients. Interphase fluorescence in situ hybridization (FISH) confirmed the RT‐PCR finding of the t(12;21) in each patient and detected the loss of the wild‐type ETV6 allele in 14 (47%) patients. Metaphase cells from only 20 patients were available for additional FISH analysis. In 13 patients, the expected fusion signal of t(12;21) was observed on der(21)t(12;21), and the reciprocal CBFA2 signal was observed on der(12)t(12;21). However, in six patients with the ETV6‐CBFA2 fusion on chromosome 21, the reciprocal CBFA2 signal was observed not on 12p13 but on 4q21, 4q27, 8q24, 11q24, 14q11.2, or 16p13.1. In four of these six patients, we found interstitial insertions of part of CBFA2. In another patient, the ETV6‐CBFA2 fusion was observed on 4q21 rather than on 21q. Thus, seven (35%) of the 20 patients with a t(12;21) revealed complex rearrangements. Our findings also indicate the importance of analyzing metaphase chromosomes in identifying cryptic and complex rearrangements involving ETV6 and CBFA2.

Concurrent translocations of MLL and CBFA2 (AML1) genes with new partner breakpoints in a child with secondary myelodysplastic syndrome after treatment of acute lymphoblastic leukemia.

The MLL gene at 11q23 is frequently disrupted by chromosomal translocations in de novo acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL), and in secondary leukemia induced by treatment with inhibitors of topoisomerase II, including the epipodophylotoxins. The CBFA2 gene at 21q22 is also frequently disrupted in de novo ALL and AML and less commonly in secondary AML. Rearrangements of MLL and CBFA2 have been described in de novo and secondary myelodysplastic syndrome (MDS). There have been no previous descriptions of coexisting abnormalities of MLL and CBFA2 in cases of MDS or acute leukemia. We describe a patient who developed secondary MDS after chemotherapy for hyperdiploid ALL. At the time of conversion to MDS, the patient had 46 chromosomes, with an 11q23/MLL translocation involving a new partner breakpoint at 2p23 and a 21q22/CBFA2 translocation involving a new partner breakpoint at 6p22. This report is the first to describe new partner breakpoints at 2p23 and 6p22 for MLL and CBFA2 genes, respectively, and concurrent rearrangements of these genes in a patient with secondary MDS. Genes Chromosomes Cancer 28:227–232, 2000.

Complex t(X;18)(p11.2;q11.2) with a pericentric inversion of the X chromosome in an adolescent boy with synovial sarcoma

Synovial sarcoma is the most common nonrhabdomyosarcomatous soft-tissue sarcoma in children and young adults. It is characterized by the common t(X;18)(p11.2;q11.2) that results in the fusion of SYT on chromosome 18 to one of two closely related and adjacent genes on the X chromosome, SSX1 or SSX2. Here we describe a poorly differentiated, monophasic synovial sarcoma in a 17-year-old adolescent boy. Hyperdiploidy, a t(X;18)(q13;q11), and other structural abnormalities were detected by conventional cytogenetic analysis. Fluorescence in situ hybridization with the PAC probe RP3-519N18, which is specific for the Xp11 region, resulted in a signal on the der(Xq), a finding consistent with a pericentric inversion of the X chromosome that resulted in a t(X;18)(p11.2;q11.2)inv(X)(p11.2q13). Real-time polymerase chain reaction using primer sets specific for SYT-SSX1 and SYT-SSX2 confirmed the presence of an SYT-SSX1 fusion transcript. Our finding of this unique and complex translocation in synovial sarcoma demonstrates the utility of molecular methods in confirming the diagnosis of synovial sarcoma.

A complex variant t(8;21) involving chromosome 3 in a child with acute myeloblastic leukemia with eosinophilia (AML M4Eo).

Although the classic t(8;21) has been reported in 10 pediatric patients with acute myeloid leukemia with eosinophilia (AML M4Eo), no complex variant t(8;21) in children with AML M4Eo has been previously described. In our analysis of leukemic blasts from a 4-year-old boy with AML M4Eo, conventional cytogenetics revealed that 95% of the cells had a hypodiploid line containing 45 chromosomes and a complex karyotype involving chromosomes 3, 8, and 21. Fluorescence in situ hybridization using whole chromosome painting probes for these chromosomes confirmed the cytogenetic findings. The presence of a CBFA2 - ETO fusion gene was established by fluorescence in situ hybridization and reverse-transcriptase polymerase chain reaction analysis. Thus, this report illustrates the first description of a complex variant t(8;21) involving chromosome band 3q27 in a child with AML M4Eo.

A Complex Karyotype Involving Chromosomes 3, 6, 11, 12, and 22 in Adult Acute Lymphoblastic Leukemia

Complex chromosomal abnormalities are rare in adult patients with acute lymphoblastic leukemia (ALL). Using molecular methods, we characterized a complex karyotype involving chromosomes 3, 6, 11, 12, and 22 in a 38-year-old man with ALL. Cytogenetic analysis revealed the following karyotype: 46,XY,der(3)t(3;? 6)(q22;?p21), m 6,add(11)(q23),add(12)(p13),+mar[10]/46,XY[19]. Because patients with 11q23 abnormalities have a poor prognosis and require aggressive treatment, we used fluorescence in situ hybridization (FISH) to fully characterize the abnormalities. FISH analysis showed no rearrangement of the MLL or ETV 6 -CBFA 2 (TEL-AML 1) genes; the wild-type ETV 6 allele was deleted in most cells. The revised karyotype after the FISH analysis was as follows: 46,XY,der(3)t(3;12)(p13;p?13)del(3)(q21),der(6)inv(6)(p21q21)ins(6;3)(q21;q21q25),der(11)t(3;11)(q25;q23),der(12)t(11;12)(q23;p?12),t(12;22)(p13;q13). Although structural abnormalities involving 11q23 and 12p13 bands were identified by conventional cytogenetics, this report clearly demonstrates that molecular assays are needed to fully characterize gene rearrangements, complex translocations as well as to assign patients to the appropriate treatment group.