What is primary mediastinal B-cell lymphoma (PMBCL)?

Updated: Sep 14, 2019
  • Author: Sonali M Smith, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Answer

Answer

Primary mediastinal B-cell lymphoma (PMBCL) is relatively rare B-cell non-Hodgkin lymphoma that comprises 6–12% of all diffuse large B-cell lymphomas (DLBCLs) and 2–4% of all non-Hodgkin lymphomas. PMBCL affects young adults in their third to fourth decade of life and has a slight female predominance. [1]  

PMBCL was initially recognized in the Revised European-American Classification of Lymphoid Neoplasms (REAL) as a subtype of DLBCL that involves the mediastinum. However, PMBCL became a fully recognized separate entity in 2001 when the World Health organization (WHO) identified that PMBCL represents a distinct clinicopathologic disease and should be classified as such.

Gene expression studies have confirmed that PMBCL is molecularly different from DLBCL and that it may resemble Hodgkin lymphoma. [2, 3, 4] Because of its skewed age distribution, PMBCL accounts for a much higher proportion of lymphomas in patients who have undergone autologous hematopoietic stem cell transplantation (auto-HSCT). Importantly, the majority of patients are cured with modern intensive combination chemoimmunotherapy that is often followed by either involved-field radiation or auto-HSCT. In fact, in some retrospective studies, PMBCL was shown to even have better prognosis than DLBCL when all other variables were equal. [5, 6] Important to note, however, is that the role of radiotherapy (RT) and/or auto-HSCT is being challenged in the current modern era of highly sophisticated imaging modalities such as positron emission tomography (PET) scanning. See the image below.

Example of mediastinal lymphoma at diagnosis. A la Example of mediastinal lymphoma at diagnosis. A large tumor mass is present in the anterior mediastinum, and an associated pleural effusion can also be seen.

While PMBCL is generally limited to the mediastinum, hematogenous and extranodal involvements are common in relapsed patients, who have generally a poor prognosis. [7, 8]  For more information, see B-Cell Lymphoma.

For patient education information, see Non-Hodgkin Lymphoma.


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