PRIMARY EFFUSION LYMPHOMA: A CASE REPORT OF DIAGNOSIS IN PLEURAL FLUID

Abstract

Primary Effusion Lymphoma (PEL) is a rare and highly aggressive post-germinal center B-cell neoplasm characterized by predominantly developing in serous cavities, such as the pleura, without the initial formation of solid tumor masses. Diagnosis of this entity is challenging and requires confirmation of an etiological association with human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma herpesvirus. PEL is strongly linked to immunodeficiency states, with Human Immunodeficiency Virus (HIV) infection being the main epidemiological factor, conferring a poor prognosis and a median survival of less than two years. This article reports the case of a 29-year-old male patient, HIV-positive and previously diagnosed with Kaposi's sarcoma, who developed bilateral pleural effusion. Diagnostic investigation by thoracentesis revealed serohematic pleural fluid with high cellularity of atypical cells with an immunoblastic and plasmablastic pattern. Pathological, cytological, and immunohistochemical studies were crucial for the diagnosis, demonstrating positivity for HHV-8 (LANA-1), CD30, and CD45, as well as a high cell proliferation index with Ki-67 of approximately 95% and negative for pan-B and EBV markers. The clinical and pathological findings confirmed the diagnosis of primary effusion lymphoma in an immunocompromised patient. This case reinforces the epidemiological profile of PEL, which is more prevalent in HIV-positive men, and highlights the importance of HHV-8 coinfection, which plays a role in immune evasion and oncogenesis. Given the morphological overlap with other lymphoproliferative disorders, the use of a specific immunohistochemical panel, with emphasis on HHV-8 testing, is essential for accurate diagnosis. Case reports like this are vital for deepening the clinical and pathological understanding of this rare neoplasm, guiding investigation and therapeutic decisions, such as the EPOCH regimen initiated in this case, in patients with cavitary effusions of unclear etiology and immunocompromise.