Disseminated Kaposi sarcoma presenting as an endophytic renal mass with concurrent primary effusion lymphoma: A case report.

Primary effusion lymphoma (PEL) is a rare, aggressive B-cell lymphoma associated with human herpesvirus-8 (HHV-8) and immunodeficiency, notably in untreated human immunodeficiency virus (HIV). Kaposi sarcoma (KS) is also an HHV-8-driven malignancy. Most cases of KS present with cutaneous manifestations, with less frequent visceral involvement. We present the case of a 63-year-old male with untreated HIV/AIDS who developed KS presenting as an endophytic renal mass with lymphovascular invasion and concurrent HHV-8-positive PEL. Biopsies confirmed KS in the kidney and PEL in the pleural fluid. Given profound immunosuppression, he was started on combination antiretroviral therapy and chemotherapy. This case represents a rare presentation of KS and highlights the aggressive course of HHV-8-driven malignancies in the setting of advanced HIV. Delayed antiretroviral initiation likely contributed to disease progression, emphasizing the critical role of early HIV treatment.