Plasmablastic Lymphoma Masquerading as Plasma Cell Myeloma: A Case Report.

Plasmablastic lymphoma (PBL) is an uncommon and aggressive type of B-cell lymphoma, and it primarily affects individuals with compromised immune systems, particularly human immunodeficiency virus (HIV)-positive patients. It has a strong predilection for the oral cavity and a high association with Epstein-Barr virus (EBV) infection, with only rare extra-oral and EBV-negative cases. Tumor cells in PBL are represented by immature plasma cells known as plasmablasts, a morphological appearance shared with many B-cell and plasma cell neoplasms, which makes the distinction very challenging among these entities, especially in extra-oral locations and EBV-negative cases. PBL is characterized by an aggressive clinical outcome, with a very poor prognosis. Here, we describe an unusual case involving a 72-year-old patient who was previously diagnosed with plasma cell myeloma, which exhibited unusually aggressive and refractory progression; histomorphological investigations were consistent with an extra-oral, EBV-negative PBL. The rapid disease progression and lymph node involvement along with the presence of plasmablastic morphology raised the suspicion of a PBL. Throughout this case, we highlight the importance of a complete histopathological and immunohistochemical examination with correlation with clinical manifestations to ensure a precise diagnosis, particularly in extra-oral, EBV-negative cases.