About Lymphoma > Types of Lymphoma > ??

Last update: 01/03/2008

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Background:

"Primary Mediastinal B-cell lymphoma (PMBL/PMBCL)) is a diffuse large B-cell lymphoma that arises in the thymus and mainly affects young adults.  

Molecular diagnosis of Primary Mediastinal B Cell Lymphoma has identified it as a clinically favorable subgroup of Diffuse Large B Cell Lymphoma related to Hodgkin Lymphoma ²

Gene expression profile in PMBCL:

Primary mediastinal large B cell lymphoma (PMBCL) has been thought of as a special subtype of DLBCL. Its distinct clinical presentation in younger patients with a female predominance has led to the suspicion that it constitutes a unique entity. However, reliable distinction from DLBCL has remained elusive.

Gene expression analysis has settled the question and provided surprising insight into this lymphoma's unique biology, including similarities to Hodgkin lymphoma5. Based on a core cluster signature of 46 specific genes, 35 of which are relatively overexpressed in PMBCL and 11 in DLBCL, PMBCL can be quite accurately distinguished from all other types of large B cell lymphomas.

This unique gene expression signature includes a number of regulators of T cell activation, but, even more surprisingly, over one-third of the genes that are more highly expressed in PMBCL than in other large B cell lymphomas are also characteristically over-expressed in cells from putative (regarded as) Hodgkin lymphoma cell lines.

Of particular note is the overexpression of several genes associated with nuclear factor κ B (NFκB), revealing a pivotal role for this gene complex and suggesting possible points of attack for future therapeutic agents.

In the case of PMBCL, the application of gene expression profiling has provided not only improved accuracy of diagnosis and provocative suggestions for possible targets for new therapeutic agents, but also intriguing linkages to Hodgkin lymphoma.

SOURCE: Improving Diagnosis and Treatment of Lymphomas with Gene Expression Profiling, Joseph M. Connors, M.D.  - hematology.org  
 
"Major new insights into the biology of lymphomas have resulted from the use of microarray gene expression technology to elucidate their underlying biology and to identify novel pathways for therapeutic intervention."

See WHO Classification

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Incidence:  

Mediastinal large B-cell lymphoma is a rare form of non-Hodgkin's lymphoma, accounting for about 1 in 50 of all cases,

"In REAL classification PMBL is considered a variant of diffuse large B cell lymphoma." "PMBL accounts for about 2 percent of all non Hodgkins lymphoma." ¹

Because of its skewed age distribution, PMBL accounts for a much higher proportion of both younger patients and those undergoing autologous transplantation. Uncertainty remains regarding the management of this disorder."  ⁷

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Diagnosis:   

To make an accurate diagnosis of lymphoma, a biopsy must be performed by the surgical removal (resection) of a lymph node.   If the lymph nodes within the mediastinum are the only ones affected, the biopsy is likely to be taken during a procedure known as a mediastinoscopy.

A series of tests will then be performed to determine the characteristics of the cells.  If a malignancy is determine, these characteristics will allow your doctors to determine the appropriate treatments to use when needed. 

Specific markers: 

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Common signs and symptoms: 

Other symptoms may include night sweats, unexplained high temperatures and weight loss. These are known as B symptoms.

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Resources:

1. Primary mediastinal B cell lymphoma (PMBL) in two sisters Year: 2002 
   Abstract No: 2646

2. Molecular Diagnosis of Primary Mediastinal B Cell Lymphoma Identifies a Clinically Favorable Subgroup of Diffuse Large B Cell Lymphoma Related to Hodgkin Lymphoma - jem.org 9_15_03

3. Molecular Diagnosis of Primary Mediastinal B Cell Lymphoma Identifies a Clinically Favorable Subgroup of Diffuse Large B Cell Lymphoma Related to Hodgkin Lymphoma - jem.org 9_15_03

4. Primary Mediastinal Large B Cell Lymphoma: Elucidating Optimal Therapy and Prognostic Factors; an Analysis in 141 Consecutive Patients Treated at Memorial Sloan Kettering from 1980-1999. Session Type: Oral Session - ASH 2004

5. Lymphomas: Non-Hodgkin Lymphoma - Medscape (free login req.)

6. About Mediastinal large B-cell lymphoma - Cancerbackup

7. About Mediastinal large B-cell lymphoma - Emedicine

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Treatment:

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Some patients with early-stage primary mediastinal DLBCL (PMBCL), however, may require involved-field radiation after chemotherapy. 

In a study of 50 patients with untreated PMBCL who received MACOP-B (methotrexate with leucovorin rescue, doxorubicin, cyclophosphamide, vincristine, prednisone, and bleomycin) followed by radiation, 66% had a persistently positive gallium scan after chemotherapy alone, suggesting active disease.¹³⁶ 

However, treatment of PMBCL with other regimens that do not include involved-field radiation, such as ACVBP and DA-EPOCH, have yielded good results in PMBCL.^71,135 Furthermore, rituximab has improved the outcome in DLBCL.⁷⁹ Hence, it is reasonable to limit involved-field radiation to those patients with persistently positive PET scans after such treatments.  - Medscape  06/07/2006

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