EBV NA1 [GST]

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.

BackgroundPrimary cardiac lymphomas are extremely rare entities (<2% of cardiac tumours) and the most frequent histologic type is diffuse large B-cell lymphoma (DLBCL). Fibrin-associated DLBCL (FA-DLBCL) is a very unusual form of DLBCL associated with chronic inflammation, and only case reports and small series have been described. In the heart, it usually occurs in the context of a cardiac myxoma or cardiac prostheses and it is not bulk forming. These lymphomas frequently present with non-germinal center phenotype and are associated with Epstein-Barr virus (EBV) type III latency.Case presentationWe describe a case of FA-DLBCL arising in a cardiac myxoma, with plasmacytic differentiation and type I EBV latency.ConclusionsAlthough they are very rare, FA-DLBCLs should be known for their diagnostic difficulty, due to its unspecified clinical manifestations, and for their more favourable prognosis, sometimes even without additional treatment after surgical resection.