One factor that appears to improve the treatment of Type II PEL is the addition of rituximab (a monoclonal antibody directed against and killing CD20-bearing cell) to the intensive chemotherapy regimens used to treat Type I PEL: the malignant cells in Type II PEL commonly express CD20 whereas the malignant cells in Type I PEL rarely express this cell surface marker. However, there are several cases of KSHV/HHV8-negative EBL that presented with pericardial effusions without evidence of more extensive disease that have experienced complete responses and favorable prognoses without chemotherapy or other cancer treatment (including rituximab) after simple drainage of the effusion. These cases suggest that, in addition to the presence of rituximab-sensitive CD20-bearing malignant cells, Type II PEL may be a less severe disease than Type I PEL, at lease in certain cases. Treatment
PEL is generally resistant to cancer chemotherapy drugs that are active against other B-cell lymphomas and therefore carries a poor prognosis. Overall median and 1 year survival rates in a series of 28 patients treated with chemotherapy for PEL were 6.2 months and 39.3%, respectively. In this study, the complete response rate (presumed to be temporary) to a standard CHOP chemotherapeutic regimen (i.e. cyclophosphamide doxorubicin, vincristine, and prednisone) was only 10% whereas a more intensive CHO chemotherapy regimen which included high dose methotrexate and bleomycin achieved a compete response rate (presumed temporary) of 70%.
Potentially important examples include: 1) overexpression of the APOBEC3B gene whose protein product (termed "probable DNA dC->dU-editing enzyme APOBEC-3B") contributes to the regulation of cell growth; 2) missense mutations in the IRAK1 gene which causes overactivation of its product protein, interleukin-1 receptor-associated kinase 1, and thereby overactivation of the NF-κB signaling pathway that regulates cell proliferation and survival; 3) overexpression of the AQP3 gene whose protein product, aquaporin 3, is a water channel that when overexpressed is thought to promote the progression and spread of various types of cancers; 4) overexpression of the P-selectin glycoprotein ligand-1 gene whose protein product promotes cell attachment to vascular endothelium; 5) overexpressin of the MUC1 gene whose product, the Mucin 1, cell surface associated protein, binds with P53 to inhibit cell death and interacts with beta-catenin to promote the tissue-invasiveness of cancer cells; and 6) overexpression of the MYC gene, whose product, c-Myc, is the cancer-causing MYC proto-oncogene although this overexpression, unlike the c-Myc overexpression occurring in other B-cell lymphomas, is usually not associated with structural abnormalities in its gene but rather is often overexpressed due to the action of the LANA-1 protein made by KSHV/HHV8. The identification of these changes in tissue samples can assist in making the diagnosis of PEL. Diagnosis
In classical cavitary cases, the diagnosis of PEL may be suspected based on its presentation as effusions in one or more bodily cavities in individuals with a history of the immunodeficiencies cited above. The diagnosis is supported by microscopic examination of cytologic smears taken from these effusions.