How is primary mediastinal B-cell lymphoma (PMBCL) differentiated from diffuse large B-cell lymphoma (DLBCL)?

Updated: Sep 14, 2019
  • Author: Sonali M Smith, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Differentiating PMBCL from other malignancies that involve the mediastinum is extremely important because the diagnosis affects management and outcome. [19] Similarly important is differentiating PMBCL from systemic diffuse large B-cell lymphoma (DLBCL) with mediastinal involvement. This latter entity often affects older patients and usually has involvement of distant lymph nodes (away from the mediastinum) and for some, bone marrow is affected with disease.

Distinguishing Hodgkin lymphoma from PMBCL can be challenging. Both diseases can affect younger adults and both entities can be similar histologically. Flow cytometry studies can be helpful, as many patients with classic Hodgkin lymphoma have neoplastic cells that express CD15 and CD30, while they lack expression of B-cell markers. As mentioned above, PMBCL patients express B-cell markers and have weak CD30 expression.

Despite significant advances, cases continue to be difficult to diagnose. Some patients have features similar to classic Hodgkin lymphoma (CHL) and PMBCL at the same time. These patients are diagnosed with mediastinal gray zone lymphoma (MGZL), which is described as B-cell lymphoma with features intermediate between DLBCL and CHL. Prognosis is worse than that of both CHL and PMBCL. Management of these patients is not well defined, but National Comprehensive Cancer Network (NCCN) guidelines recommend treatment with aggressive DLBCL regimens. [20]  Data suggest that adding rituximab to chemotherapy regimens improves outcomes. [20, 21]  

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