EBV positive plasmacytoma in immunocompetent patients: A diagnostically challenging rare entity

Abstract

Abstract Introduction/Objective Epstein-Barr Virus (EBV)-positive plasmacytoma is a rare entity that shows morphological and immunophenotypic overlap with plasmablastic lymphoma and can cause a diagnostic dilemma. Here we discuss a unique case of EBER-positive plasmacytoma arising from nasal polyps. Methods/Case Report A 61-year-old immunocompetent male presented with nasal polyps, right maxillary sinus lesions, and an enlarging sternal lesion. Multiple biopsies were obtained which revealed a diffuse infiltration by atypical plasma cells, that were positive for CD138, MUM1, CD79a, CD56, lambda-in situ hybridization, and Ki67- proliferation index of 20-30%. In situ, hybridization for EBV-encoded viral RNA (EBER) was positive in the neoplastic cells. B- and T- cell markers were negative. The flow cytometry studies detected monotypic lambda-restricted CD38/CD138 positive plasma cells with an aberrant expression of CD56 and CD117. Molecular studies for B-and T- cell gene rearrangement were also negative. A final diagnosis of EBER-positive plasmacytoma was made. The patient was treated with cyclophosphamide, vincristine, doxorubicin, and carboplatin followed by four cycles of RVD, and is doing well. Results (if a Case Study enter NA) NA Conclusion EBER-positive plasmacytoma poses a diagnostic challenge with plasmablastic lymphoma, specifically in immunocompetent individuals. The useful differentiating clues pointing towards EBER positive plasmacytoma could be a spectrum of morphology ranging from mature to anaplastic, low Ki67 proliferation index, aberrant CD56 and CD117 positivity, and high M- spike on protein studies. Comprehensive clinical, morphologic phenotypic, and genetic investigations are necessary to make a specific diagnosis as the two entities differ in their management.