Gastrointestinal Plasmablastic Lymphoma in an Immunocompetent 44‐Year‐Old Woman

Plasmablastic lymphoma (PBL) is classified by the World Health Organization (WHO) as a type of diffuse large B‐cell lymphoma (DLBCL) that is characteristically aggressive with a morphology of a diffuse proliferation of large cells. These cells display an immunoblast/plasmablast‐like morphology and exhibit a plasma cell immunophenotype. They are positive for markers such as CD138, CD38, and MUM1, while lacking expression of typical pan‐B‐cell markers, which include CD20, CD79a, and CD19. Typically, it presents as an extra nodal, oral cavity–related proliferation associated with HIV infection. Other sites of presentation have been described. The gastrointestinal (GI) tract is recognized as a leading extranodal site of PBL, being the second most frequent presentation site. The GI involvement is significantly common in HIV‐negative patients, accounting for approximately 20%–30% of cases. Although not fully understood, its pathogenesis has been strongly associated with two factors: Epstein–Barr virus (EBV) infection, detected in approximately 60%–75% of cases, and MYC gene alterations. Differentials include undifferentiated carcinomas, neuroendocrine neoplasms, metastatic tumors, and other plasma cell proliferations. Diagnostic techniques include EBV probes, and MYC rearrangement is present in a small number of cases. These findings are useful in differentiating other types of lymphomas with similar morphology: anaplastic lymphoma kinase positive, DLBCL, and DLBCL with plasmacytoid differentiation. This case report is aimed at presenting a patient with PBL that does not conform to the usual clinical presentation yet exemplifies the morphological and ancillary findings of a PBL with some challenging characteristics that should be considered in the identification of PBL.