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Abstract Introduction: HIV-associated Plasmablastic Lymphoma (PBL) stands as a rare subset of Diffuse Large B-cell Lymphoma (DLBCL), marked as an AIDS-defining malignancy. The primary presentation site is the oral cavity. Although extra-oral PBLs have been reported, these are considered to be very rare. Despite its scarcity, understanding its pathogenesis, diagnosis, and management remains paramount. Herein, we elucidate a distinctive case of HIV-associated PBL manifesting in the anal cavity, an infrequent site, accompanied by an intriguing immunohistochemical signature. Clinical Course: A 30-year-old male presented with symptoms indicative of an anal mass, ultimately diagnosed as Plasmablastic Lymphoma. Further evaluation disclosed a pulmonary nodule and a substantial anal-perineum mass. Given the concurrent HIV infection, initiation of retroviral therapy was crucial alongside lymphoma-directed treatment. Notably, immunohistochemical analysis revealed an unusual profile, encompassing positive expression for CD45, CD38, MYC, OCT2, and MUM1, alongside a heightened Ki-67 proliferation index. Conversely, markers such as CD20, PAX5, Pankeratin, CK7, CK20, MART1, CD30, HHV8 CD138 and P63 exhibited negativity. Epstein-Barr virus (EBV) presence was detected. Treatment initiation comprised HyperCVAD chemotherapy, supplemented by intrathecal chemotherapy and methotrexate. Discussion: Immunophenotypically, PBL conventionally lacks CD45, CD20, and CD79a expression while expressing CD38, CD138, and MUM1. However, our case deviated with positive CD45 expression and negative CD138. Treatment paradigms for HIV-associated PBL encompass intensive regimens such as CHOP-alike regimens with other intensive alternatives such as CODOX-M/IVAC, DA-EPOCH or Hyper-CVAD therapy, with limited intrathecal agent utilization to avert central nervous system involvement. Despite aggressive therapeutic measures, prognosis remains guarded. The progression free survival rates range between 6 and 7 months, with median overall survival falling within the 11 to 13 month range. Long-term survivors predominantly emerge among pediatric patients, underscoring potential disparities in disease biology and treatment response. Conclusion: This case epitomizes the heterogeneity and intricacy inherent in HIV-associated Plasmablastic Lymphoma. The unconventional presentation in the anal cavity, coupled with an atypical immunohistochemical profile, poses challenges to diagnostic and therapeutic strategies. Collaborative efforts with specialized centers are imperative for optimal disease management, accentuating the imperative for sustained research endeavors to enhance outcomes in this aggressive lymphoma variant. Citation Format: Aliya M Khan, Mehmet Hepgur, Sophia Navajas. Unveiling the complexity of HIV-associated plasmablastic lymphoma: A case report of anal cavity presentation with unconventional immunohistochemical profile abstract. In: Proceedings of the Fourth AACR International Meeting on Advances in Malignant Lymphoma: Maximizing the Basic-Translational Interface for Clinical Application; 2024 Jun 19-22; Philadelphia, PA. Philadelphia (PA): AACR; Blood Cancer Discov 2024;5 (3Suppl): Abstract nr PO-033.
Khan et al. (Wed,) studied this question.