Primary effusion lymphoma

**Definition:** An aggressive non-Hodgkin B-cell lymphoma composed of large cells, presenting as a serous effusion without detectable tumour masses. It is universally associated with human herpes virus 8 (HHV-8)/Kaposi sarcoma herpes virus (KSHV) [HHV-8/KSHV]. It mostly occurs in the setting of immunodeficiency; most cases have been reported in HIV positive patients. The most common sites of involvement are the pleural, pericardial, and peritoneal cavities. The prognosis is extremely unfavorable.