A Rare Case of Systemic Epstein-Barr Virus-Positive Diffuse Large B-Cell Lymphoma With Hemophagocytic Lymphohistiocytosis in an Immunocompetent Young Man: Potential Diagnostic Pitfall and Therapeutic Challenge.

Epstein-Barr virus-positive diffuse large B-cell lymphoma (EBV⁺ DLBCL) is an uncommon subtype of aggressive B-cell lymphoma, with both nodal and extranodal involvement being exceedingly rare. We present a unique case of a 32-year-old immunocompetent male with a nasopharynx lesion accompanied by fever and bilateral cervical lymphadenopathy. The initial biopsy from the nasopharynx proposed infectious mononucleosis (IM) as a potential diagnostic pitfall. The further discovery of lymph node and intestinal mucosa biopsies confirmed the diagnosis of systemic EBV⁺ DLBCL. After receiving four cycles of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) treatment, the patient got complete remission. However, hemophagocytic lymphohistiocytosis (HLH) developed following the fifth cycle of CHOP. The patient accepted allogeneic hematopoietic stem cell transplantation (allo-HCT) subsequently. Unfortunately, the survival time was only 14 months. Appeals for a multi-dimension approach to understanding more fully and improving the outcomes of such cases are underscored.