FISH identifies different types of duplications with 12q13-15 as the commonly involved segment in B-cell lymphoproliferative malignancies characterized by partial trisomy 12

Clinical, cytogenetic, fluorescence in situ hybridization (FISH), and Southern blot data of 18 patients with different subtypes of B-cell non-Hodgkin's lymphoma, cytogenetically characterized by partial trisomy 12, are presented. These chromosomal changes occurred predominantly in clinically progressive chronic lymphocytic leukemia, mixed cell type, and advanced-stage follicle center cell lymphoma at the time of relapse or transformation into diffuse large cell lymphoma. Partial trisomy 12 consistently included the long arm of chromosome 12, either completely or partially, and resulted from dup(12q) or other rearrangements involving chromosome 12. The duplications were cytogenetically identified as dup(12)(q13q23), dup(12)(q13q22), or dup(12)(q13q15) in follicle center cell lymphoma or t(14;18)-positive diffuse large cell lymphoma; dup(12)(q13q22) or dup(12)(q13q24) in chronic lymphocytic leukemia; and dup(12)(q13q21) in a case of t(14;18)-negative diffuse large cell lymphoma. FISH, using library probes and a panel of YAC probes, mapped along the long arm of chromosome 12, confirmed the cytogenetic results in all cases analyzed except for three cases of t(14;18)-positive follicle center lymphoma or diffuse large cell lymphoma with dup(12q). In these cases, FISH showed similar, possibly identical, duplications, which involved a region more centromeric (12q11-21) than assumed by karyotypic analysis (12q13-22 or 12q13-23) and included alphoid DNA sequences, a combination hitherto unknown. In addition, commonly duplicated regions of chromosome 12 could be defined: 12q11-21, including alphoid DNA sequences for follicle center cell lymphoma or t(14;18)-positive diffuse large cell lymphoma, 12q13-22 for chronic lymphocytic leukemia, and 12p13-q15 for marginal zone cell lymphoma, all of which overlapped in 12q13-15. Whether these regions, especially 12q13-15, may contain genes which are important in malignant transformation or disease progression of B-cell lymphoproliferative malignancies characterized by complete or partial trisomy 12 remains to be determined.

BCL6 gene rearrangements also occur in marginal zone B-cell lymphoma

Marginal zone B-cell lymphoma (MZBCL) represents a distinct subtype of B-cell non-Hodgkin's lymphoma (NHL) which has been recently recognized and defined as a disease entity. Cytogenetically, these lymphomas reveal a high prevalence of trisomy 3, and recent data obtained by comparative genomic hybridization indicate that the chromosomal regions 3q21-23 and 3q25-29 might be of particular pathogenetic significance. We identified structural chromosomal abnormalities involving the region 3q27 and rearrangements of the BCL6 proto-oncogene in three out of 34 (9%) well-defined cases of extranodal, nodal and splenic MZBCL using cytogenetic analysis. Southern blot, and fluorescence in situ hybridization (FISH). All three cases were characterized by a t(3;14)(q27;q32). Two of them showed additional chromosomal abnormalities including trisomy 3, which was found in one case. The patients displayed extranodal disease and did not demonstrate any striking clinical and histological differences when compared with MZBCL lacking BCL6 rearrangement. The present study for the first time demonstrates the occurrence of t(3;14)/BCL6 gene rearrangement in MZBCL, thus suggesting a role of the BCL6 proto-oncogene in the pathogenesis of MZBCL.

The monoclonal antibody ALK1 identifies a distinct morphological subtype of anaplastic large cell lymphoma associated with 2p23/ALK rearrangements

Anaplastic large cell lymphoma (ALCL) is a heterogeneous group of diseases by morphology, phenotype, genotype, and clinical presentation. Using a new monoclonal antibody (ALK1) that recognizes the native anaplastic lymphoma kinase (ALK) protein as well as the fusion product of the t(2;5)(p23;q35), nucleophosmin (NPM)/ALK, we investigated for ALK expression cases diagnosed as ALCL as well as lympho-proliferative disorders possessing overlapping features with ALCL. Thirteen cases showed cytoplasmic staining of the neoplastic cells. These cases were characterized by a fairly uniform morphology and occurred in children and young adults as a systemic disease. All other cases comprising T or null ALCL (17 cases), B ALCL (8 cases), Hodgkin's disease (HD) (15 cases), HD-like ALCL (23 cases), and lymphomatoid papulosis (9 cases), were negative for ALK expression. Translocation t(2;5)(p23;q35) was found by classical cytogenetics or interphase fluorescence in situ hybridization in 8 of the ALK1-positive cases and by reverse transcription-polymerase chain reaction in 1 other case. Two additional ALK1-positive cases with an abnormal karyotype, but without t(2;5)(p23;q35), showed by fluorescence in situ hybridization analysis a cryptic NPM/ALK gene fusion caused by an insertion of ALK near NPM in one case and a translocation of ALK to 2q35 as a result of an indiscernible inv(2)(p23q35) in the other. The latter variant translocation points to a localization of an unknown gene at 2q35 that, like NPM, might deregulate ALK and be involved in the pathogenesis of ALCL. In summary, immunohistochemistry with ALK1 antibody allows the identification of a distinct subgroup within the ALCL of T or null phenotype that is associated with 2p23 abnormalities and lacks the marked histological pleomorphism described in ALCL in general. Whereas immunostaining is the most sensitive method to identify this group, it does not help to additionally clarify the relationship among ALCL, HD, and HD-like ALCL.

Marginal zone B-cell lymphomas including mucosa-associated lymphoid tissue type lymphoma (MALT), monocytoid B-cell lymphoma and splenic marginal zone cell lymphoma and their relation to the reactive marginal zone

The marginal zone of the B follicle represents a well-defined compartment of the B area. Its cellular composition is distinct from that of the follicle centre, from which it also differs in its functional role in the immune response. Several newly identified lymphoma entities, e.g. extranodal MALT type lymphoma, nodal monocytoid B-cell lymphoma and splenic marginal zone B-cell lymphoma, display in common a very peculiar organoid growth pattern reminiscent of the marginal zone. Moreover, their neoplastic components share morphologic and phenotypic similarities to the cellular components of the marginal zone. The clinical characteristics of these various marginal zone cell lymphomas may differ depending of the organ which is involved. Nevertheless, they all share common cytogenetic abnormalities suggesting a common pathogenesis.

Characteristic pattern of chromosomal gains and losses in marginal zone B cell lymphoma detected by comparative genomic hybridization

Marginal zone B cell lymphoma (MZBCL) represents a distinct subtype of B cell non-Hodgkin's lymphoma, which has been recently recognized and defined as a disease entity. We investigated 25 cases (18 at primary diagnosis and seven during the course of disease) of MZBCL by comparative genomic hybridization (CGH) and compared these results with cytogenetic, fluorescence in situ hybridization (FISH), and Southern blot data. Twenty of the 25 cases (80%) showed gains (total 49) or losses (total 15) of genetic material. In extranodal, nodal, and splenic MZBCL, material of chromosomes 3 (52% of cases), 18 (32%), X (24%), and 1q (16%) was most frequently gained, whereas losses predominantly involved chromosomes 17 (16%) and 9 (12%). High-level amplifications involving the regions 18q21-23 and 18q21-22, respectively, were detected in two cases. Gains of chromosomes 1q and 8q and losses of chromosome 17 or 17p occurred more frequently in relapsed or progressive lymphomas. For all of the frequently affected chromosomes, CGH allowed narrowing of the relevant subregions including 3q21-23, 3q25-29 and 18q21-23. By Southern blot analysis, the BCL2, BCL6, and CMYC proto-oncogenes were found to be a part of the over-represented regions in two cases, one case, and two cases, respectively, with gains involving 18q, 3q or 8q. In 13 cases, CGH revealed chromosomal imbalances which were not detected by cytogenetic analysis but could be confirmed by FISH or Southern blot analysis in all cases investigated. On the other hand, CGH failed to detect trisomy 3, trisomy 18, and deletion 7q in three cases with a low proportion of tumor cells bearing these abnormalities, as shown by interphase FISH. The characteristic pattern of chromosomal gains and losses detected in this study confirms the distinct nature of MZBCL and may point to chromosomal regions involved in the pathogenesis of these neoplasms.

A new subtype of pre-B acute lymphoblastic leukemia with t(5;12)(q31q33;p12), molecularly and cytogenetically distinct from t(5;12) in chronic myelomonocytic leukemia

Translocation t(5;12)(q33;p13), resulting in an ETV6/PDGFRB gene fusion, is a recurrent chromosomal abnormality associated with chronic myelomonocytic leukemia (CMML). An analogous translocation was also found in four cell lines with features of pre-B acute lymphoblastic leukemia (ALL). Using fluorescence in situ hybridization (FISH) we show here that in three of these cell lines identical complex rearrangements occurred. However, the regions involved on 5q and 12p are different from the breakpoints in CMML, and the translocation is accompanied by seemingly identical cryptic deletions of both 5q and 12p chromosome sequences in all analyzed pre-B ALL cell lines. The similar cytogenetic, FISH, and immunophenotyping findings in the three cell lines suggest that the t(5;12)(q31q33;p12) defines a new entity of pre-B ALL.

Genetic abnormalities in chronic lymphocytic leukemia and their clinical and prognostic implications

Clonal chromosome abnormalities can be detected in approximately 50% of patients with chronic lymphocytic leukemia (CLL). The most common changes are trisomy 12, followed by structural abnormalities of 13q, 11q, 6q, and 14q. By fluorescence in situ hybridization (FISH), these aberrations can be demonstrated even in cases with insufficient mitotic yield or a normal karyotype. The biologic consequences of trisomy 12 are unknown, but a gene dosage effect is suspected and studies on partial trisomy 12 indicate that the region 12q13 to 12q22 might be of particular pathogenetic importance. Trisomy 12 is strongly associated with atypical lymphocyte morphology and seems to be a secondary event in leukemogenesis, as shown by combined immunophenotyping and interphase FISH. Structural abnormalities of 13q frequently involve hetero- and homozygous deletions of a region in 13q14, distal to the retinoblastoma gene, which may be the site of a tumor suppressor gene. In contrast to a normal karyotype or structural changes of 13q, complex karyotypic abnormalities, high percentage of abnormal metaphases, trisomy 12 and structural changes involving the P53 tumor suppressor gene on 17p13 are adverse prognostic indicators. Cytogenetic and molecular findings provide important diagnostic, clinical, and prognostic information which can contribute to treatment decisions and follow-up of CLL patients.

t(14;19)/BCL3 rearrangements in lymphoproliferative disorders: a review of 23 cases

The t(14;19)(q32.3;q13.2) is a rare but recurrent translocation found in patients with B-cell malignancies, mainly in chronic B-cell lymphoproliferative disorders. When occurring in chronic lymphocytic leukemia (CLL), atypical lymphocyte morphology and immunophenotype have been reported. A high proportion of patients with CLL and t(14;19) are aged less than 40 years. t(14;19) is often associated with rapidly progressive disease, and overall prognosis is poor compared to the expected survival in chronic lymphocytic leukemia and low-grade B-cell lymphoma. t(14;19) is rarely the sole cytogenetic aberration. Trisomy 12 is the most frequent associated abnormality, and is observed in 50% of cases. t(14;19) involves the BCL3 gene, which is located at the breakpoint on chromosome 19 and is juxtaposed to the immunoglobulin heavy chain gene locus on chromosome 14 (often in the switch alpha region) in a "head-to-head" configuration. The translocation does not interrupt the transcriptional integrity of BCL3, but is associated with overexpression of this gene, which encodes an I kappa B-like protein and modulates the activity of the NF-kappa B transcription factors. The genes affected by overexpression of BCL3 remain to be identified.

Fusion of ETV6 to MDS1/EVI1 as a result of t(3;12)(q26;p13) in myeloproliferative disorders

We identified a fusion between ETV6 on 12p13 and MDS1/EVI1 on 3q26 in a t(3;12)(q26;p13) found in two cases of myeloproliferative disorder. The resulting chimeric transcript consists of the first two exons of ETV6 fused to MDS1 sequences, which in turn is fused to the second exon of the EVI1 gene. It has recently been reported that MDS1 can be expressed in normal tissues both as a single gene and fused to EVI1. ETV6 does not contribute any known functional domain to the predicted fusion protein. Association with blast crisis and myelodysplastic syndrome-derived leukemia, bad prognosis, and relative complex karyotype are in agreement with observations made in other cases of t(3;12)(q26;p13). Furthermore, a comparison can be made with the formation of an AML1/MDS1/EVI1 fusion gene in translocations (3;21)(q26;q22).

del(7q) in chronic B-cell lymphoid malignancies

Twelve patients with diagnosis of B-cell non-Hodgkin's lymphoma/leukemia and del[7q] were studied for their clinical, cytogenetic, and molecular characteristics. Eleven patients were classified as small cell lymphoma whereas one had a diffuse large cell lymphoma. Lymphoplasmacytic features were observed in six out of eleven small cell lymphomas. Morphologically and immunologically these small cell lymphomas could be classified as chronic lymphocytic leukemia (typical or atypical; 4 cases), marginal zone lymphoma (splenic lymphoma with villous lymphocytes; 1 case), mantle cell lymphoma (2 cases), or nonspecified, non-Hodgkin's lymphoma (4 cases). Eleven of twelve patients presented with peripheral blood and bone marrow involvement. Two of twelve cases showed del[7q] as the sole anomaly. Two different types of deletions were present: ten cases had del(7)(q21q31) and two cases had del(7)(q31q34). Cases that could be molecularly investigated did not show any involvement of BCL2, BCL3, or BCL6, and only one case had BCL1 rearrangement. The data indicate that del(7q) is associated with a subset of mature small B-cell lymphoproliferative disorders of which some but not all show lymphoplasmatic features.

ETV6 gene rearrangements in hematopoietic malignant disorders

Chromosomal abnormalities involving the short arm of chromosome 12 have been frequently observed in a broad spectrum of hematological malignancies. Recently, a gene located in this chromosomal region and implicated in leukemogenesis was identified. The gene, called ETV6 (previously known as TEL) is a new member of the ETS family, a group of genes thought to act as transcriptional activators. The gene spans 240 kb and consists of eight exons coding for a helix-loop-helix (HLH) and a DNA-binding domain. ETV6 was originally identified in a t(5;12)(q33;p13) occurring in a chronic myelomonocytic leukemia (CMML). Recent reports, however, show its involvement in a growing number of translocations associated with myeloid as well as lymphoid leukemias. At the molecular level fusions of ETV6 with PDGFRB (5q33), ABL (9q34), MNI(22q11) and AML1(21q22) have already been identified. Analysis of these chimeric proteins indicates that distinct domains of ETV6 can be involved in different fusion products, thus ETV6 can provide transcriptional and dimerization properties for partner genes, or the gene itself can act as an altered transcriptional factor. At least two clinico-pathological entities associated with ETV6 rearrangements have emerged as distinct disorders. The first one is a chronic myeloid malignancy characterized by t(5;12)(q33;p13), monocytosis and/or eosinophilia. The second entity is a type of childhood acute lymphoblastic leukemia (ALL) hallmarked by t(12;21)(p13;q22), and is shown to be the most frequent but cytogenetically largely undetectable chromosomal anomaly in childhood ALL.

Successful use of the same slide for consecutive fluorescence in situ hybridization experiments

The feasibility of using the same slide repeatedly for fluorescence in situ hybridization (FISH) experiments was systematically evaluated by applying standard procedures and various combinations of direct- and indirect-labeled probes to slides from patients with hematologic malignancies. Specific and distinct hybridization signals along with weak background signals and chromosome morphology of good to moderate quality could be obtained in up to three experiments performed consecutively on the same slide. Signals related to biotin- or digoxigenin-labeled probes applied in previous hybridizations were still visible with variable intensity, but interpretation problems that may result from this signal noise can be avoided by using adequate probes, detection systems and fluorochromes, and sequence of experiments.

ider(9)(q10)t(9;22)(q34;q11) is a recurrent chromosomal abnormality in acute lymphoblastic leukemia and lymphatic blastic phase of chronic myelogenous leukemia

We report on two cases, one with acute lymphoblastic leukemia and a second with lymphatic blastic phase of Philadelphia chromosome-positive chronic myelogenous leukemia, cytogenetically characterized by ider(9)(q10)t(9;22)(q34;q11). Our findings and the data of the 4 cases previously published indicate that ider(9)(q10)t(9;22)(q34;q11) represents a rare but recurrent chromosomal abnormality occurring in hematological malignancies with lymphoid differentiation, namely acute lymphoblastic leukemia and lymphatic blastic phase of chronic myelogenous leukemia, and most likely evolves from a preexistent der(9) involved in the standard t(9;22).

BCL-6 expression in reactive lymphoid tissue and in B-cell non-Hodgkin's lymphomas

Chromosomal abnormalities involving 3q27 have recently been associated with diffuse large B-cell lymphomas and, less frequently, with follicular lymphomas. Molecular studies have led to the identification of the BCL-6/LAZ-3 gene, located at 3q27 and coding for a putative zinc-finger protein that might act as a transcriptional regulator during cell differentiation and development. Rearrangement of BCL-6 results in truncation of the gene in its 5' portion, leaving the protein intact; a resultant deregulation of its expression has been hypothesized. In order to test this hypothesis, the expression of BCL-6 protein was investigated in human reactive lymphoid tissue and compared with a group of non-Hodgkin's lymphomas (NHLs) with or without 3q27 anomalies and/or BCL-6 gene rearrangement. BCL-6 protein is consistently expressed in reactive lymphoid tissues, where it is restricted to the follicle centre. The protein is also widely expressed in NHL: all follicular lymphomas tested showed a pattern of expression similar to the reactive B follicle, independently of the presence of BCL-6 gene rearrangement and/or 3q27 anomalies. In the diffuse large B-cell lymphomas, there was more variation in BCL-6 expression, but a correlation with 3q27 anomalies and/or BCL-6 rearrangement was not found. Deregulation of the BCL-6 gene did not result in an aberrant tissue expression as detected by immunohistochemistry.

Biallelic alterations of both ETV6 and CDKN1B genes in a t(12;21) childhood acute lymphoblastic leukemia case

Recently, a new recurrent t(12;21)(pl3;q22) has been identified in a B-cell lineage childhood acute lymphoblastic leukemia (ALL). The translocation results in a fusion of two known genes, ETV6/TEL (12p13) and AML1 (21q22), previously shown to be involved in the pathogenesis of myeloid disorders. We report results of cytogenetic fluorescence in situ hybridization and molecular studies of a B-cell childhood common ALL with a cryptic 12;21 translocation. Aberrations identified in this case involve both chromosomes 12 and include not only the ETV6-AML1 gene fusion and two different microdeletions of ETV6 but also the hemizygous loss of CDKN1B, D12S119, and KRAS2 loci and a putative rearrangement of the second CDKN1B allele as a result of an inv(12)(p13q24). Moreover, it was shown that the AML1-ETV6 reciprocal chimeric transcript was not present in the malignant cells, and hence may not play a major role in leukemogenesis. In addition, the putative loss of wild-type function of CDKN1B and ETV6 could indicate a synergistic effect of both genes in the pathogenesis of this leukemia case.

Small B cell NHL and their leukemic counterpart: differences in subtyping and assessment of leukemic spread

Three subtypes of small lymphocytic lymphoma were studied, namely B cell chronic lymphocytic leukemia (B-CLL), mantle cell lymphoma (MCL) and follicle center lymphoma (FCL). Agreement between tissue diagnosis, based on the proposal for a revised European-American classification of lymphoid neoplasms from the International Lymphoma Study Group, and the cytomorphological diagnosis on peripheral blood and/or bone marrow smears, using the proposals for the classification of chronic (mature) B and T lymphoid leukemias of the French-American-British Cooperative Group, was studied. Full agreement was found in 90% of the CLL and 82% of the FCL cases. In MCL cases, agreement was 65% including all cases classified as intermediate/mantle zone lymphoma according to FAB criteria. The incidence of bone marrow involvement detection in trephines compared to smears was equal in CLL (both 100%) and slightly higher in MCL (56 vs 48.5%); in FCL, however, trephine biopsies provided more reliable material (71 vs 35%).

Trisomy 3 in marginal zone B-cell lymphoma: a study based on cytogenetic analysis and fluorescence in situ hybridization

Trisomy 3 represents the most frequent and consistent chromosomal abnormality characterizing the recently defined entity marginal zone B-cell lymphoma (MZBCL). By cytogenetic analysis and/or fluorescence in situ hybridization (FISH) on interphase nuclei we found in increased copy number of chromosome 3 in 22/36 (61%) successfully analysed cases, including 8/12 cases with extranodal MZBCL, 8/13 cases with nodal MZBCL, and 6/11 patients with splenic MZBCL. Sensitivity of interphase cytogenetics was somewhat higher than that of conventional cytogenetic investigation. Structural chromosomal changes involving at least one chromosome 3 were seen in 11/20 cases with an increased copy number of chromosome 3: +de(3)(p13) was demonstrated in three cases, and was the sole chromosomal abnormality in one of them; +i(3)(q10) was seen in two other patients; and rearrangements involving various breakpoints on the long arm of chromosome 3 were found in the remaining cases. FISH on metaphase spreads confirmed these structural abnormalities and additionally showed two unexpected translocations involving chromosome 3. We conclude that: (1) trisomy 3 occurs in a high proportion of extranodal, nodal and splenic MZBCL; (2) FISH on interphase nuclei is an additional and sensitive tool in detecting an increased copy number of chromosome 3 in MZBCL; (3) additional structural abnormalities involving the long arm of chromosome 3 are frequent but non-recurrent and are perhaps secondary changes; and (4) abnormalities such as +del(3)(pl3) and +i(3)(q10) suggest that genes located on the long arm of chromosome 3 are of particular importance in the pathogenesis of MZBCL.

De novo 46,XX, dir dup (11)(q133.3-->q14.2) in a patient with mental retardation, congenital cardiopathy and thrombopenia

A 31-year-old female is reported with mild to moderate mental retardation, facial dysmorphy, congenital cardiopathy, and mild thrombocytopenia as the most important clinical findings. Chromosome analysis in lymphocytes showed a de novo dir dup (11)(q13.3-->14.2), by both G-banding and FISH techniques. Previously reported constitutional duplications of 11q are mostly the result of unbalanced translocations involving chromosome 11q, and are associated with a partial monosomy or trisomy of the translocation partner chromosome. In case of an unbalanced translocation it is not clear which clinical findings result from the chromosome 11 duplication and which result from the abnormality on the translocation partner chromosome. This is the first report on a constitutional duplication of chromosome region 11q13.3-->14.2 without involvement of other chromosomes.

"Small" B-cell non-Hodgkin's lymphomas with splenomegaly at presentation are either mantle cell lymphoma or marginal zone cell lymphoma. A study based on histology, cytology, immunohistochemistry, and cytogenetic analysis

Only 1 to 2% of all non-Hodgkin's lymphomas (NHL) present with an enlarged spleen, most of them "small B-cell lymphomas." Recently, several reports have identified these lymphomas as marginal zone B-cell lymphomas. We reviewed 39 cases of NHL presenting with an enlarged spleen without lymphadenopathy, documented by fixed and frozen material. Two were peripheral T-cell lymphomas, four diffuse large B-cell lymphomas, and 14 hairy cell leukemias. The remaining 19 belonged to the "small B-cell" category and constitute the focus of our study. Subtyping was achieved by combining morphology, immunophenotype, and cytogenetic features according to the proposal of the International Lymphoma Study Group; in addition, analysis of the peripheral blood and bone marrow smears was performed adopting the French-American-British (FAB) criteria. From this study, we can conclude that most "small B-cell" NHL of the spleen were either mantle cell lymphomas or marginal zone cell lymphomas and, by peripheral blood analysis, that the mantle cell lymphomas corresponded to intermediate lymphocytic lymphoma and the marginal zone cell lymphomas to splenic lymphomas with villous lymphocytes. As a result, several diagnostic criteria can be proposed that may be helpful in differentiating mantle cell lymphoma from marginal zone cell lymphoma in the spleen.

Marginal zone B-cell lymphomas of different sites share similar cytogenetic and morphologic features

Clinical, histologic, cytogenetic, and molecular genetic data of 31 patients with extranodal, nodal, and splenic marginal zone B-cell lymphoma (MZBCL) are presented. Despite these variable clinical manifestations, a similar spectrum of morphologic features as well as distinctive immunophenotypic findings were noted. In all cases, a monotypic B-cell proliferation consistently negative for CD5, CD10, and CD23 was found expanding the marginal zone of the B follicle with and without colonization of the follicle centers. Clonal chromosomal abnormalities were detected in 23 of the 31 patients. Recurrent aberrations included whole or partial trisomy 3 (18 cases), trisomy 18 (9 cases), and structural rearrangements of chromosome 1 with breakpoints in 1q21 (9 cases) or 1p34 (6 cases), all of which were seen in extranodal, nodal, as well as splenic MZBCL. Abnormalities of the additional chromosome 3, such as +del(3)(p13),+i(3)(q10), or structural changes involving the distal part of the long arm, were evident in 9 of the 18 cases. All recurrent abnormalities were found in MZBCL more frequently than in other histologic entities of B-cell non-Hodgkin's lymphoma (B-NHL). None of the known lymphoma-associated chromosomal changes or rearrangements of the BCL1, BCL2, BCL3, BCL6, and CMYC genes were detected. We conclude that MZBCL represent a distinct entity of B-NHL with characteristic morphologic and immunophenotypic features and particular chromosomal abnormalities, and that a close histogenetic relationship between extranodal, nodal, and splenic MZBCL is likely, although the clinical presentation may vary.

Assignment of the gene encoding human Krüppel-related zinc finger protein 4 (GLI4) to 8q24.3 by fluorescent in situ hybridization

The gene for human Krüppel-related protein 4, (HKR4, gene symbol GLI4), a zinc finger protein of unknown function, has been localized by fluorescence in situ hybridization to chromosome 8q24.3, distal to c-MYC.

The ETV6, CDKN1B and D12S178 loci are involved in a segment commonly deleted in various 12p aberration in different hematological malignancies

Structural rearrangements including deletions of the short arm of chromosome 12 are frequent cytogenetic findings in various hematologic malignant disorders. Using FISH with a panel of DNA probes we detected loss of a common region of 12p in 22 patients with different hematologic disorders. Nine of them were characterized cytogenetically by a del(12p), seven by unbalanced translocations, and in the remaining cases the loss of the 12p region was masked by translocations and insertions, adding extra material to the short arm of chromosome 12. The smallest commonly deleted region found in all cases analyzed included ETV6, the gene for p27kipl (CDKN1B), and the D12S178 marker.

Translocation (Y;1)(q12;q12) in hematologic malignancies. Report on two new cases, FISH characterization, and review of the literature

Translocation (Y;1)(q12;q12) is a rare cytogenetic anomaly occurring in hematologic disorders thought to affect stem cells. We report here on two new cases, one end-stage myelofibrosis and one chronic myelomonocytic leukemia. The translocation breakpoints were assessed by conventional cytogenetic techniques in both cases and by FISH in the second case. A partial trisomy of the 1q21-qter region could be demonstrated. The data of the literature are reviewed and the possible pathogenetic mechanisms are discussed.

BCL3 rearrangement and t(14;19)(q32;q13) in lymphoproliferative disorders

Translocation t(14;19)(q32;q13) is a rare but recurrent abnormality in chronic lymphocytic leukemia and small cell lymphoma. It has been associated with rearrangements of the BCL3 gene, which is located at the breakpoint on chromosome 19 and is juxtaposed to the immunoglobulin heavy chain locus on chromosome 14 as a result of the translocation. This results in transcriptional up-regulation of the BCL3 gene, which encodes a transcription coactivator, an I-kappa B protein, probably contributing to disease progression. We found, among 4,487 cytogenetic analyses of lymphoproliferative disorders, six cases with a t(14;19)(q32;q13), five of which showed the classical t(14;19)(q32;q13) and one of which showed a three-way translocation t(7;19;14)(q21;q13;q32). The 14;19 translocation never occurred as a single abnormality; additional aberrations included trisomy 12 and several structural abnormalities. The cytogenetic examination was supplemented by molecular analysis using available probes for the BCL3 locus (p alpha 1.4P and p alpha 5B) in 1,150 of the 4,487 patients. Rearrangements of BCL3 could be detected in five cases, all of which had the classical t(14;19). In the case with t(7;19;14), the suspected BCL3 involvement could only be confirmed using long-range restriction mapping, indicating that, with the usually available BCL3 probes, rearrangements of this locus may be missed.

Isodicentric (X)(q13) in haematological malignancies: presentation of five new cases, application of fluorescence in situ hybridization (FISH) and review of the literature

Idic(X)(q13) represents a rare but recurrent chromosomal abnormality in haematological malignancies. We present five new cases characterized by this particular aberration and review the literature on this subject. The patients were elderly females with a diagnosis of refractory anaemia (1/5), refractory anaemia with ringed sideroblasts (2/5), chronic myelomonocytic leukaemia (1/5), and Philadelphia chromosome-negative chronic myeloid leukaemia (1/5). Three out of the five patients demonstrated an increased proportion of bone marrow ringed sideroblasts. After a follow-up period of 30-57 months all patients but one are alive. Idic(X)(q13) always occurred as the sole chromosomal abnormality, either in one or in two copies. We confirmed the dicentric nature of the aberration by fluorescence in situ hybridization (FISH) on metaphases as well as interphase nuclei using an X-chromosome-specific alpha-satellite probe, and performed chromosome painting to visualize possible additional chromosomal changes involving the X chromosomes. Our findings and the data of 17 previously published cases indicate that idic(X)(q13): (1) may play a significant pathogenetic role in haematological malignancies affecting exclusively females and deriving predominantly from early progenitor cells; (2) is frequently associated with a pathological iron accumulation; (3) indicates a variable prognosis.