De novo acute B-cell leukemia with translocation t(14;18): an entity with a poor prognosis.

Three cases of de novo acute B-cell lymphoblastic leukemia are presented, all with an unusual phenotype, involvement of translocation t(14;18) and additional chromosomal abnormalities, including translocation t(8;14) and deletion of chromosome 9. In contrast to normal FAB-L2 or FAB-L3 acute lymphoblastic leukemia (ALL), these leukemias did not express cytoplasmatic and membranous immunoglobulin. The combination of translocation t(14;18) and additional chromosomal events on the other chromosome 14 account for the lack of immunoglobulin expression. In one case a low grade follicular lymphoma was found next to a high grade Burkitt type ALL. The translocation t(14;18) takes place as a mistake in the VDJH joining in pre-B cells in the bone marrow. It is proposed that some cases of de novo ALL may arise as a blast crisis induced by genetic events, secondary to the primary t(14;18) translocation. This type of ALL seems to have a poor prognosis.

Chromosomal translocation t(14;19) as indicated by bcl-3 rearrangement is a rare phenomenon in non-Hodgkin's lymphoma and chronic lymphocytic leukemia: a molecular genetic analysis of 176 cases.

Using a probe for the newly described bcl-3 gene near the breakpoint of the t(14;19), 176 cases of non-Hodgkin lymphoma and B cell chronic lymphocytic leukemia were analyzed. Rearrangement of the bcl-3 gene was found in only one case; a follicular lymphoma involving the salivary gland that had progressed to a diffuse large cell lymphoma. We conclude that rearrangement of the bcl-3 gene as detected by our method occurs rarely in mature B or T cell neoplasms.

Mosaicism of trisomy 12 in chronic lymphocytic leukemia detected by non-radioactive in situ hybridization.

Cytogenetic analysis using banding techniques of B-chronic lymphocytic leukemia (CLL) is hampered by the difficult in vitro proliferation of these tumor cells. For detection of specific cytogenetic aberrations these problems can be overcome with non-radioactive in situ hybridization (ISH). ISH may especially be applied for the detection of trisomy 12, which is the most frequent cytogenetic aberration in CLL. Sixty-seven patients with CLL, four normal controls and one lymphoblastoid B-cell line with a trisomy 12 were studied using a chromosome 12 specific probe. To determine the hybridization properties of the CLL cells, all samples were also hybridized with probes specific for chromosomes 1 and 8. All leukemias were analyzed by immunocytochemistry to determine the proportion of tumor cells. Eight cases (11%) showed a trisomy 12. After correction for the number of tumor cells, it was demonstrated that in almost all cases (7 out of 8), the aberration was present in a proportion of the tumor cells (between 30 and 72%). Except for one patient this mosaicism persisted with long-term follow-up. We conclude that the in vivo incidence of trisomy 12 in CLL is approximately 11%, and that trisomy 12 occurs in most instances in only a subpopulation of the leukemic cells. Both findings suggest that trisomy 12 in CLL is a late event.

Histological conversion of follicular lymphoma with structural alterations of t(14;18) and immunoglobin genes.

About half of the patients with follicular lymphoma will develop an aggressive B cell lymphoma with morphological changes in growth pattern and cellular morphology. Changes of the immunophenotype, especially of the expression of immunoglobulin (Ig) have been documented less frequently. Multiple tumor samples of two patients with follicular lymphoma who developed tumor progression, were studied by Southern blot analysis for rearrangements of the Ig genes and the oncogenes BCL2 and MYC. In both patients, the general pattern of Ig gene rearrangements, especially of the Ig light-chain genes, and the structure of the t(14;18) breakpoint as assessed by the polymerase chain reaction (PRC) and fine restriction mapping, remained unaltered with time. However, both within the functional Ig heavy-chain allele and around the t(14;18) breakpoint, extensive secondary alterations took place. This indicates clonal evolution rather than the appearance of an independent lymphoma. In the first case with progression from follicular lymphoma to Burkitt's lymphoma 3 years after diagnosis, alterations were especially present 3' of the t(14;18) breakpoint. In the second patient with a change from follicular to diffuse centroblastic lymphoma 4 years after diagnosis, subsequent class switches from IgM to IgG and to defective IgH expression were accompanied by deletion of C mu sequences and a rearrangement of the MYC gene, respectively. Additionally, in both patients alterations in individual restriction sites occurred, which most likely were due to somatic mutations within both the functional IgH and translocated allele. Our data indicate that complex alterations of both the functional and non-functional IgH allele may accompany tumor progression and may erroneously suggest the appearance of independent clones by Southern blot analysis. It remains to be established whether these alterations are causative events or the consequence of genetic instability and clonal evolution.

Molecular genetics of gastrointestinal non-Hodgkin's lymphomas: unusual prevalence and pattern of c-myc rearrangements in aggressive lymphomas.

Thirty-two extranodal lymphomas of the gastrointestinal (GI) tract underwent molecular genetic analysis by Southern blotting using probes for the immunoglobulin genes and the bcl-1, bcl-2, and c-myc loci, commonly involved in lymphomagenesis. No bcl-1 rearrangements were found. There was only one large-cell lymphoma with a bcl-2 rearrangement. A rearrangement of the c-myc gene was found in six of eight Burkittlike lymphomas of the intestine. In five of these six cases, a chromosomal translocation t(8;14) with an unusual breakpoint was demonstrated by comigration of the rearranged c-myc and a rearranged JH sequence. This pattern of rearrangement has not been previously associated with a specific group of non-Hodgkin's lymphomas. In contrast to all six low-grade lymphomas, c-myc rearrangements were found in 6 of 12 large-cell or high-grade mucosa-associated lymphomas of the stomach. No comigration of c-myc and immunoglobulin heavy-chain gene sequences were found. We conclude that primary GI lymphomas have different molecular genetic characteristics compared with node-based follicle center-cell lymphoma and as a group are not related to these lymphomas. In addition, the prevalence and patterns of c-myc rearrangements in the gastric large-cell lymphomas and ileocecal Burkittlike lymphomas are noteworthy and suggest a different and distinct pathogenesis for these tumors.

Oncogene rearrangements in chronic B-cell leukemia.

Forty-four B-chronic lymphocytic leukemias (CLL) were studied by Southern blot analysis using probes for the Ig genes and bcl-1, bcl-2 (major, minor and 5' breakpoint region), bcl-3, c-myc, and retinoblastoma (Rb) loci. Eight cases had three or more rearranged JH bands, indicating oligoclonality, clonal evolution, or chromosomal translocation. One case had a rearrangement of the bcl-1 locus and three of the bcl-2 locus. In the first case, comigration of the rearranged bcl-1 and JH sequences indicated a t(11;14)(q13;q32) translocation, which, in contrast to previously described cases, seems to be completely reciprocal. One case with a bcl-2 rearrangement showed comigration of the bcl-2 major breakpoint region and a rearranged JH band. This indicates a t(14;18) (q32;q21). The two other cases showed rearrangements of the bcl-2 5' breakpoint region without apparent comigration. No rearrangements were detected of c-myc and bcl-3, located at chromosome 19, nor was a deletion of Rb found. All but three cases had CD5 expression. The exceptions included the t(11;14) and the t(14;18) cases. Our results confirm recent data on rearrangements at the 5' site of bcl-2 in CLL. Additionally, they corroborate the presumption that CD5-negative chronic B-cell leukemias should be considered apart from classical CLL.

Essential differences in oncogene involvement between primary nodal and extranodal large cell lymphoma.

Large cell lymphomas (LCLs) are heterogeneous in morphology, clinical presentation, and behavior. We studied 52 de novo LCLs of B-cell type for rearrangements of the bcl-2 and c-myc oncogenes by Southern blot analysis and related these data to the primary site of presentation, stage, and cytomorphology. Thirteen tumors had comigrating rearrangements of JH and bcl-2, indicative of a t(14;18). Far more primary nodal lymphomas than extranodal lymphomas carried a t(14;18) (40% v less than 5%). Additionally, almost all lymphomas with a t(14;18) versus 41% of the tumors without a bcl-2 rearrangement presented with lymphadenopathy. c-myc rearrangements were seen in 35% of the extranodal lymphomas and 5% of the nodal lymphomas. No differences were observed in bone marrow involvement and staging according to Ann Arbor. bcl-2 rearrangements were found in 50% of the LCLs with cleaved nuclei, whereas c-myc rearrangements were relatively frequent (25%) in the noncleaved subtype. Our data support the hypothesis that primary nodal and extranodal lymphomas have a different genetic origin.