A cancerous proliferation of lymphocytic B-cells caused by the human herpesvirus 8 (HHV-8, Kaposi's sarcoma-associated herpesvirus). It is more prevalent in immunodeficient people such as AIDS patients. The cancer tends to occur in the lining of body cavities such as the pericardium and peritoneum. The cancerous cells are detected in the fluid secreted from the lining of the cavity. See also Primary effusion lymphoma