Key result
Rare EBV-positive PMBL case with XPO1 mutation suggests EBV positivity should not exclude diagnosis.
Why the study?
The distinction between PMBL and other mediastinal lymphomas is challenging, and EBV positivity is uncommon but can occur in PMBL, complicating diagnosis.
Case Report (n=1)
EBV positivity can occur in rare PMBLs and should not exclude the diagnosis, while XPO1 mutations can provide diagnostic support and potential targeted therapeutic options.
EBV positivity should not exclude PMBL in young adults; this case leaves open XPO1 mutation utility for diagnosis and targeted therapy.
Primary mediastinal (thymic) large B-cell lymphoma (PMBL) is described as almost always negative for Epstein-Barr virus (EBV). In the context of a mediastinal lymphoma, the distinction between PMBL, classical Hodgkin lymphoma, diffuse large B-cell lymphoma, and mediastinal gray-zone lymphoma can be very difficult; hence, EBV positivity often argues against PMBL. We present a 19-year-old man with mediastinal mass morphologically consistent with PMBL. The tumor expressed classic immunophenotype, including positivity for CD20, CD19, MAL, OCT2, BOB1, BCL6, CD79a, and subset positivity for CD30. However, the tumor was EBV-positive by in situ hybridization. Next-generation sequencing detected somatic mutations in XPO1 (E571K), SMARCB1 (L356fs), and MYCC (T73A). Although the immunophenotype and XPO1 mutation are characteristic of PMBL, EBV expression is uncommon. Since EBV positivity can occur in rare PMBLs, it should not be the deciding factor in the diagnosis. This is the first EBV-positive PMBL in which mutational profiling has been reported. Aside from providing diagnostic support, the finding of the XPO1 E571K mutation may suggest a targeted therapeutic option.
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Maracaja et al. (2019) conducted a case report in Primary mediastinal (thymic) large B-cell lymphoma (PMBL) (n=1). Immunohistochemistry and next-generation sequencing was evaluated on Diagnosis and mutational profiling of EBV-positive PMBL. A 19-year-old man was diagnosed with a rare EBV-positive primary mediastinal large B-cell lymphoma featuring an XPO1 E571K mutation, suggesting EBV positivity should not exclude PMBL diagnosis.
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