Abstract
Background
Primary mediastinal (thymic) large B-cell lymphoma (PMBL) is described to be almost always negative for EBV in the current WHO. In the context of a mediastinal lymphoma, the distinction between PMBL, classic Hodgkin lymphoma (CHL), diffuse large B-cell lymphoma, and mediastinal gray-zone lymphoma can be very difficult; hence, EBV positivity often aids in pointing away from a diagnosis of PMBL. However, since EBV positivity can occur in rare PMBLs, it should not be the deciding factor in the diagnosis; assistance from molecular studies is emerging in these difficult cases.
Case Presentation
We present a 19-year-old male patient with a 2-week history of cough, vocal changes, and occasional dysphagia who was found upon imaging to have a 6-cm mediastinal mass. The biopsy of this mass was morphologically consistent with PMBL but the tumor was EBV positive by in situ hybridization.
Methods
We performed next-generation sequencing using Oncomine Comprehensive Assay v3 (ThermoFisher Scientific) on formalin-fixed, paraffin-embedded tumor tissue with a buccal swab sample for germline control. Variant calling, filtering, and annotation were performed by the Yale Tumor Profiling Laboratory.
Results
We found somatic mutations in XPO1, SMARCB1, and MYC. Along with classic immunophenotype of PMBL including positivity for MAL, OCT2, BOB1, BCL6, CD79a, MUM1, CD20, and subset weak CD30, the diagnosis was confirmed to be PMBL.
Conclusion
This is the first EBV-positive PMBL in which molecular profiling was performed. XPO1, specifically the mutation hotspot (E571K), found in our case is involved in PMBL and CHL. This was clinically helpful in confirming the histopathologic diagnosis and also opening up a targeted therapeutic option. Selective inhibitors of nuclear export (SINEs) that block the binding of XPO1 to its cargo are in clinical development as antineoplastic agents and have shown promising activity against some hematologic malignancies.
BRACHIAL PLEXOPATHY AND CARDIAC TAMPONADE: AN UNCOMMON PRESENTATION OF DIFFUSE LARGE B-CELL MEDIASTINAL LYMPHOMA
