Translocation (2;9)(p12;p23) in a case of acute leukemia with t(4;11)(q21;q23). Lack of rearrangement of the kappa and interferon gene loci

Characteristic chromosomal imbalances in primary central nervous system lymphomas of the diffuse large B-cell type

We performed a genome wide screening for genomic alterations on a series of 19 sporadic primary central nervous system lymphomas (PCNSL) of the diffuse large B-cell type by comparative genomic hybridization (CGH). The tumors were additionally analyzed for amplification and rearrangement of the BCL2 gene at 18q21 as well as for mutation of the recently cloned BCL10 gene at 1p22. Eighteen tumors showed genomic imbalances on CGH analysis. On average, 2.1 losses and 4.7 gains were detected per tumor. The chromosome arm most frequently affected by losses of genomic material was 6q (47%) with a commonly deleted region mapping to 6q21-q22. The most frequent gains involved chromosome arms 12q (63%), 18q and 22q (37% each), as well as 1q, 9q, 11q, 12p, 16p and 17q (26% each). High-level amplifications were mapped to 9p23-p24 (1 tumor) and to 18q21-q23 (2 tumors). However, PCR-based analysis, Southern blot analysis and high-resolution matrix-CGH of the BCL2 gene revealed neither evidence for amplification nor for genetic rearrangement. Mutational analysis of BCL10 in 16 PCNSL identified four distinct sequence polymorphisms but no mutation. Taken together, our data do not support a role of BCL2 rearrangement/amplification and BCL10 mutation in PCNSL but indicate a number of novel chromosomal regions that likely carry yet unknown tumor suppressor genes or proto-oncogenes involved in the pathogenesis of these tumors.

Primary mediastinal B-cell lymphoma: a review of pathology and management

PURPOSE

Primary mediastinal B-cell lymphoma (PMBL) is recognized as a separate disease entity in the REAL classification. There is uncertainty about the relevance and especially the optimal management of this disorder. In this review, we discuss clinical presentation, pathology, pathobiology, and management of PMBL in order to provide a platform for initiation of further clinical and biologic studies.

MATERIALS AND METHODS

Studies were identified through a MEDLINE search and from the bibliographies of relevant articles.

RESULTS

PMBL is a tumor of young adults who present with a rapidly proliferating tumor. At diagnosis, the tumor is usually limited to intrathoracic organs. Spread to parenchymal organs such as liver, kidneys, and CNS is common at recurrence. Fibrosis and the presence of so-called clear cells are distinctive morphologic features of PMBL, although they are not pathognomonic or even necessary for diagnosis. On the other hand, biologic features relating to oncogene rearrangement and overexpression as well as cytogenetic features clearly differentiate PMBL from other types of diffuse large B-cell lymphoma. Phase II studies and retrospective series indicate cure rates that range from 38% to 88%. The role of chemotherapy, radiation, and high-dose chemotherapy with stem cell rescue in the management of PMBL is reviewed.

CONCLUSION

PMBL has unique clinical and biologic characteristics that are radically different from those of other types of diffuse large B-cell lymphoma. Although relatively rare, its aggressive growth and its occurrence in young patients increase the clinical relevance of this entity. The consistent recognition and study of PMBL will allow the development of new approaches to its management.

Cloning and mapping of the MEIS1 gene, the human homolog of a murine leukemogenic gene

The mammalian homeobox genes encode a family of transcription factors that are important in a wide range of cellular processes, including hematopoiesis. Aberrant expression of some homeobox genes is known to be oncogenic. We report the cloning and initial characterization of a human homeobox gene, MEIS1, identified in a survey of homeobox genes expressed in the human fetal liver. The complete cDNA sequence shows that MEIS1 is likely to be the human homolog of Meis1, a mouse gene that is known to be activated in myeloid leukemia by retroviral insertion. We found that the MEIS1 gene is expressed at low levels in normal immunohematopoietic tissues, including the fetal liver. However, consistent with its possible role in myeloid leukemogenesis, MEIS1 was expressed in a subset of myeloid leukemia cell lines, with the highest expression seen in those with a megakaryocytic-erythroid phenotype. The gene is also expressed at high levels in the cerebellum. The gene is located on human chromosome region 2p13-p14 and contains the previously identified anonymous markers D2S134 and NIB1519. Whether this gene, which is leukemogenic in mice, also plays a leukemogenic role in humans will require further study.

Association between t(2;9)(p12;p23) and early B-precursor acute lymphoblastic leukemia

We report the occurrence of t(2;9)(p12;p23) in a 20-month-old girl with early B-precursor acute lymphoblastic leukemia (ALL). This translocation has only been reported once before in an adult case of early B-precursor ALL with t(4;11)(q21;q23). We suggest that t(2;9)(p12;p23) may be associated with this particular phenotype of ALL.