A dual colour dual fusion fluorescence in situ hybridisation study on the genesis of complex variant translocations in chronic myelogenous leukaemia

Complex variant 9;22 translocations occur in a significant minority of chronic myelogenous leukaemia (CML) patients. Different mechanisms of their formation have been described. We report dual colour dual fusion fluorescence in situ hybridisation data in 12 Chinese CML patients with complex translocations. Three previously reported breakpoint hotspots in a third partner chromosome (14q32, 17q25, 1q21) were observed. In 10/12 (83.3%) patients, the abnormality occurred as a single step 3-break event. Only a single abnormal clone harbouring the complex translocation was seen in this group. The remaining 2 cases in the chronic phase showed a 4-break mechanism (2/12, 16.7%). Deletion of 5' ABL at der(9) was not observed in any of the 12 patients, however, the loss of 3' BCR was observed in 1 patient (1/12, 8.3%). Together with previous findings, these data suggest that these variant translocations occur more often as a 3-break single-step process with no reciprocal ABL-BCR fusion. On the other hand, a 4-break event is also regularly seen during the initial stages of leukaemogenesis, which likely predisposes to der(9) deletion. The observed difference in rates of der(9) deletion reported in a series of CML patients with variant translocations may be related to a difference in rates of a 4-break event.

Functional alterations of Lin-CD34+CD38+ cells in chronic myelomonocytic leukemia and on progression to acute leukemia

The functional behavior of hematopoietic stem cell (HSC) and progenitors in chronic myelomonocytic leukemia (CMML) and on disease progression is little known. We performed cell proliferation, apoptosis, hematopoietic colony forming/replating and differentiation potential studies in the purified subpopulations of Lin(-)CD34(+)CD38(-) and Lin(-)CD34(+)CD38(+) cells from 16 CMML with 6 cases after acute myeloid leukemia transformation (AML-t). We observed an expansion of the hematopoietic progenitor pool (Lin(-)CD34(+) cells) in AML-t comprising mainly Lin(-)CD34(+)CD38(+) cells. The Lin(-)CD34(+)CD38(+) cells in AML-t displayed high proliferative activity, resistance to apoptosis, enhanced myeloid colony formation/replating ability and a complete dendritic cell (DC) differentiation block. Our findings suggest Lin(-)CD34(+)CD38(+) cells instead of Lin(-)CD34(+)CD38(-) cells could be the target(s) of secondary genetic lesions underpinning progression from CMML to AML, which have implications for the further study of the biology of leukemic transformation and the design of new strategies for the effective treatment of CMML.

Diagnostic utility of dual fusion PML/RARalpha translocation DNA probe (D-FISH) in acute promyelocytic leukemia

Translocation(15;17) leading to the formation of fusion gene PML/RARalpha is the diagnostic hallmark of acute promyelocytic leukemia (APL). Interphase fluorescence in situ hybridization (FISH) is one of the diagnostic tools employed for the detection of PML/RARalpha rearrangement. Using a dual color dual fusion (D-FISH) PML/RARalpha translocation DNA probe which hybridises both to PML/RARalpha and RARalpha/PML fusion genes, we characterised the FISH pattern of 52 APL patients at diagnosis and correlated the findings with conventional cytogenetics and RT-PCR analysis. The diagnostic sensitivity of the probe for PML/RARalpha was 100%. Seven patients had atypical D-FISH patterns; two had a masked PML/RARalpha fusion signal caused by the insertion of PML into RARalpha on 17q; 3 had an extra copy of PML/RARalpha in the form of isochromosome der(17)(q10)t(15;17) and one had duplication of the normal RARalpha gene with an ider(17q) masquerading as i(17)(q10). There was also one case of t(7;17;15) with a typical D-FISH pattern and in which metaphase FISH suggested an unusual 4-point break. In summary, PML/RARalpha D-FISH is a highly sensitive method for confirming diagnosis of APL. However D-FISH cannot be solely relied on for the diagnosis of APL owing to atypical patterns which are infrequently observed in cases with additional 17q structural abnormalities, gene insertion and gene duplication.

A novel beta-delta globin gene fusion, anti-Lepore Hong Kong, leads to overexpression of delta globin chain and a mild thalassaemia intermedia phenotype when co-inherited with beta(0)-thalassaemia

Anti-Lepore haemoglobins (Hb) are rare betadelta fusion variants that arise from non-homologous crossover during meiosis, resulting in a delta-betadelta-beta configuration. A novel anti-Lepore mutation (anti-Lepore Hong Kong) was found in two Chinese families with raised Hb A(2). Direct sequencing revealed a crossover within a 54-bp region spanning the junction of cap site (CAP) and exon 1, which predicted the production of normal delta-globin. Determination of alpha/beta-mRNA ratios by quantitative real-time polymerase chain reaction demonstrated downregulation of the beta gene in cis due to the interposed betadelta fusion gene. Although heterozygotes have normal red cell indices and are clinically silent, compound heterozygotes with beta(0) mutation in trans produce a mild thalassaemia intermedia phenotype with a markedly raised Hb A(2) level that may mimic clinically mild Hb E-beta(+)-thalassaemia. Awareness of the presence of anti-Lepore Hong Kong will help to resolve diagnostic problems in regions with significant prevalence of globin disorders.

A laboratory strategy for genotyping haemoglobin H disease in the Chinese

BACKGROUND

The thalassaemias are the commonest blood disorders worldwide, with South East Asia and southern China as areas of high prevalence. Accurate diagnosis of these disorders helps in clinical management with improved outcome.

METHODS

The alpha-globin genotypes of 100 Chinese patients in Hong Kong with haemoglobin H (Hb H) disease were characterised. Single-tube multiplex gap-PCR was used to detect --(SEA), -alpha(3.7) and -alpha(4.2), while Hb CS, Hb QS and codon 30 (DeltaGAG) were identified by single-tube multiplex amplification refractory mutation system (ARMS). Automated direct nucleotide sequencing of the amplified alpha2- and alpha1-globin genes was performed to characterise other non-deletional alpha-thalassaemia determinants.

RESULTS

In the 100 cases studied, 99 cases had --(SEA) in combination with deletional alpha(+)-thalassaemia or non-deletional alpha-globin gene mutation involving the alpha2-globin gene. In 70 cases of the deletional form, 43 cases showed the genotype of (--(SEA)/-alpha(3.7)) and 27 cases of (--(SEA)/-alpha(4.2)). Three of the 27 cases of (--(SEA)/-alpha(4.2)) were found to have Hb Q-Thailand linked in-cis with -alpha(4.2). The remaining 30 cases were of non-deletional form with the following genotypes: 11 cases of (--(SEA)/alpha(HbCS)alpha), 9 cases of (--(SEA)/alpha(HbQS)alpha), 3 cases of (--(SEA)/alpha(cd30 (DeltaGAG))alpha), 3 cases of (--(SEA)/alpha(cd31)alpha), 2 cases of (--(SEA)/alpha(poly-A)alpha), 1 case of (--(SEA)/alpha(HbWestmead)alpha) and 1 case of (--(non-SEA)/alpha(HbQS)alpha).

CONCLUSIONS

Based on two rapid diagnostic tests, multiplex gap-PCR and multiplex ARMS, more than 90% of the cases were genetically characterised. This laboratory strategy should be widely applicable for genetic diagnosis of alpha-thalassaemia.

High BCL6 expression predicts better prognosis, independent of BCL6 translocation status, translocation partner, or BCL6-deregulating mutations, in gastric lymphoma

To investigate the role of BCL6 in the pathogenesis of gastric lymphoma, we analyzed the BCL6 promoter region for BCL6 translocations, somatic hypermutations, and deregulating mutations in 43 gastric lymphomas, including 4 extranodal marginal-zone B-cell lymphomas of mucosa-associated lymphoid tissues (MALT lymphomas), 33 diffuse large B-cell lymphomas (DLBCLs), and 6 composite DLBCLs with residual MALT lymphoma (DLCLMLs). BCL6 promoter substitutions by immunoglobulin (Ig) and non-Ig translocation partners, resulting in its deregulation, were frequently involved in DLBCL (36.4%) and DLCLML (50%). Two novel BCL6 translocation partner genes, 28S rRNA and DMRT1, and a new BCL6 translocation breakpoint in intron 2 were also identified. Deregulating mutations were found only in DLBCL (24.2%), which correlated significantly with high BCL6 protein expression. Significantly, high BCL6 expression correlated strongly with longer overall survival (OS), independent of mechanism in gastric DLBCL and DLCLML. Gastric DLBCLs were further subclassified into germinal center B-cell-like (GCB) and non-GCB subgroups immunohistochemically. High BCL6 expression was detected in all GCB cases, irrespective of BCL6 genetic alterations. In the non-GCB subgroup, BCL6-deregulating mutations correlated significantly with high BCL6 expression level. No significant correlation was found between the BCL6 expression level and OS in the non-GCB subgroup, which had significantly poorer prognosis than the GCB subgroup.

Diffuse large B-cell lymphoma with occult marrow involvement and a novel t(9;10)(q32;q22)

A 33-year-old man was found to have stage IV diffuse large cell lymphoma with visceral, cutaneous, and central nervous system involvement. Although examination of the posttreatment bone marrow failed to show morphologic evidence of lymphoma involvement, cytogenetic study of the marrow mononuclear cells showed the presence of a clonal abnormality t(9;10)(q32;q22), a hitherto undescribed chromosomal abnormality in diffuse large B-cell lymphoma.

Arsenic trioxide in comparison with chemotherapy and bone marrow transplantation for the treatment of relapsed acute promyelocytic leukaemia

BACKGROUND

The best overall treatment strategy for patients with acute promyelocytic leukaemia (APL) in relapse with chemotherapy, bone marrow transplantation (BMT) or arsenic trioxide (As(2)O(3)) based therapy remains undefined.

PATIENTS AND METHODS

We reviewed the clinical course and treatment outcome of 143 APL cases seen in four major hospitals in Hong Kong over a 10-year period.

RESULTS

Complete remission (CR) was attained in 113 cases (79%) with all-trans retinoic acid (ATRA) and chemotherapy. Relapse occurred at a median of 16 months in 54 cases, with a 3-year disease free survival of 56%. Post-relapse treatment was successful in 41 cases (76%), giving an actuarial 3-year overall survival (OS) of 81% from CR1. Three different protocols were used: chemotherapy alone (n = 19), allogeneic BMT (n = 14) and an As(2)O(3)-based regimen (n = 21). Chemotherapy was associated with the highest treatment-related mortality (TRM) at 53%, giving a CR2 rate of 47%. TRM was 36% for BMT. The CR2 rate for the As(2)O(3)-based regimen was 100%, with no TRM. However, 38% of As(2)O(3) treated patients had subsequent relapses, which were further salvaged in 75% by combined As(2)O(3) plus ATRA. The actuarial OS for the three protocols leveled off by 2 years at 82% for As(2)O(3), 43% for BMT and 23% for chemotherapy (P = 0.0004).

CONCLUSIONS

Our results suggest that As(2)O(3) may be superior to chemotherapy and BMT for the treatment of APL in relapse.

Cytomegalovirus infection associated with clonal proliferation of T-cell large granular lymphocytes: causal or casual?

Clonal proliferation of T-cell large granular lymphocytes (LGL) is an indolent disorder characterized by splenomegaly, lymphocytosis and frequent manifestations of immune disturbances. The LGL are CD3(+) CD4(-) CD8(+) CD56(-). The clonality of the tumor cell population is often only demonstrable by T-cell receptor (TCR) gene rearrangement study because chromosomal abnormality is distinctly rare. We describe a case of T-cell LGL leukemia that presented initially as cytomegalovirus infection. The leukemic LGL are shown to be clonal by both TCR gene rearrangement and chromosomal studies. They persist after subsidence of the cytomegalovirus infection.

Consolidation therapy with autologous blood stem cell transplantation in a patient with primary plasma cell leukaemia

Primary plasma cell leukaemia (PPCL) is a rare form of plasma cell dyscrasia. Conventional melphalan-based treatment is often ineffective, with a reported median survival of 2-7 months only. We report a 53-year-old man with PPCL who was treated with four cycles of combination chemotherapy including vincristine, adriamycin and dexamethasone that resulted in a good partial remission. High-dose melphalan 200 mg/m2 and autologous peripheral blood stem cell (PBSC) rescue was then given 6 months after diagnosis. Maintenance interferon-alpha was started 8 weeks after transplantation with good drug compliance. Complete remission was achieved and molecular remission was documented 11 months after autologous PBSC transplantation. In conclusion, high-dose therapy followed by autologous stem cell rescue is a feasible option for PPCL that can result in a reasonably sustained remission.

A novel t(2;3)(q31;p13) in acute myelocytic leukemia

We report a case of acute myelocytic leukemia without maturation exhibiting a novel t(2;3)(q31;p13). Conventional cytogenetics showed the concomitant occurrence of a single metaphase with 47,XX,+8. Nevertheless, interphase cytogenetics by fluorescence in situ hybridization using a chromosome 8 alpha-satellite DNA probe showed that the percentage of cells with three hybridization signals was within the control range.

Hypoplastic myelodysplastic syndrome-a clinical, morphologic, or genetic diagnosis?

We report a middle-aged female with an 11-year history of nonprogressive pancytopenia and severely hypoplastic marrow with minimal morphologic dysplasia. A diagnosis of hypoplastic myelodysplastic syndrome (MDS) was made because of the finding of a persistent clonal abnormality, del(13)(q12q14), and the subsequent demonstration of a single Auer rod-containing blast in the peripheral blood smear. The case illustrates the problems in the differentiation between aplastic anemia and hypoplastic MDS.

Precursor T-lymphoblastic leukemia with a novel t(1;22)(p34;q13)

A 37-year-old woman that presented with cervical lymphadenopathy and leukocytosis was found to have precursor T-lymphoblastic leukemia (T-ALL). Cytogenetic study of the leukemic cells showed a 46,XX, t(1;22)(p34;q13) karyotype. The t(1;22)(p34;q13) is a novel chromosomal abnormality in human malignancies and is probably a variant form of the t(1;14)(p34;q11) found in precursor T-ALL.

Gain of chromosome 3/3q in B-cell chronic lymphoproliferative disorder is associated with plasmacytoid differentiation with or without IgM overproduction

Trisomy 3 has been reported to be associated with marginal zone B-cell lymphoma. However, its occurrence and significance in other B-cell chronic lymphoproliferative disorders has not been fully defined. We report five cases of B-cell chronic lymphoproliferative disorders showing gain of chromosome 3 or 3q. The patients were elderly males who presented with splenomegaly with or without hepatomegaly and lymphadenopathy. The diagnoses included chronic lymphocytic leukemia (3 cases), prolymphocytic leukemia (1 case), and Waldenstrom macroglobulinemia (1 case). Distinctive feature in this group of patients was the plasmacytoid appearance of the leukemic lymphocytes, with an associated IgM hypergammaglobulinemia in three patients. The relationship between the gain of chromosome 3 and plasmacytoid differentiation in B-cell chronic lymphoproliferative disorders is discussed.

Idiopathic myelofibrosis with extramedullary haemopoiesis involving the urinary bladder in a Chinese lady

Extramedullary haemopoiesis (EMH) associated with idiopathic myelofibrosis most commonly involves the reticuloendothelial organs, such as the spleen and liver, although ectopic haemopoietic tissue has also been described rarely in the lymph nodes, skin, gastrointestinal tract, pleura, peritoneum, central nervous system, and genital and urinary tracts. We report on a 54-year-old Chinese lady with a long history of idiopathic myelofibrosis who presented with gross haematuria and left hydronephrosis due to EMH in the bladder trigone. Cystoscopic examination revealed a sessile necrotic papillary growth at the trigone, obstructing the left ureteric orifice. Transurethral resection of the bladder tumour was performed, and microscopic examination of the tumour chips demonstrated atypical megakaryocytes, immature granulocytes and normoblasts, confirming the presence of EMH. The residual bladder tumour responded well to low dose radiotherapy, with subsequent disappearance of haematuria and normalization of ultrasonogram findings.

Chronic lymphocytic leukemia with a novel der(8;15)(q10;q10) translocation

A 71-year-old male was found to have chronic lymphocytic leukemia. Cytogenetic study of the leukemic lymphocytes shows a 46,XY,der(8;15)+15. The der(8;15) is a novel chromosomal abnormality in human malignancies. The resulting loss of 8p and trisomy 15q are both unusual chromosomal changes in chronic lymphocytic leukemia.

Sinonasal angiosarcoma with marrow involvement at presentation mimicking malignant lymphoma: cytogenetic analysis using multiple techniques

Angiosarcoma of the head and neck most commonly involves the skin of the scalp or face; primary involvement of the sinonasal region is exceedingly rate. We report a patient with sinonasal angiosarcoma who showed marrow involvement at presentation. Marrow aspiration smears showed many large, often segregated blast-like cells, mimicking malignant lymphoma. However, trephine biopsy revealed formation of anastomosing vascular spaces by the tumor cells and immunoreactivity for CD31, supporting a diagnosis of angiosarcoma. DNA ploidy analysis showed an apparent diploidy. Nevertheless, conventional cytogenetics demonstrated very complex chromosomal abnormalities with the presence of multiple hypodiploid clones, together with several near-triploid to near-tetraploid clones showing structural abnormalities involving chromosomes 1, 3, 4, 9, 14, 16, 17, 18, and 22. The identification of these karyotypic changes has been facilitated by the application of comparative genomic hybridization and spectral karyotyping.