The clonality of tumor-infiltrating lymphocytes in African Kaposi's sarcoma

Background: African Kaposi's sarcoma (KS) lesions contain human herpesvirus -8 (HHV-8) and Epstein-Barr virus (EBV, both of which are associated with v arious types of non-Hodgkin's lymphomas and are known to produce several fa ctors suspected of lymphomagenic potential. The aim of this study was to ev aluate tumor-infiltrating lymphocytes for the evidence of clonal expansion in African KS. Methods: We used polymerase chain reaction (PCR)-based assays to determine the clonality of tumor-infiltrating lymphocytes in African KS lesions and c ompared the results to similar studies of patient-matched uninvolved skin a nd peripheral blood. Results: T cells were polyclonal in all samples tested. Peripheral blood B cells were also polyclonal; however, a minority of lesional and uninvolved skin samples exhibited evidence of restricted B-cell clonality. Correlation with immunohistological analysis revealed that this clonal B-cell restrict ion was secondary to the sparse nature of lesional B cells rather than thei r clonal overgrowth. Conclusions: We conclude that, despite the putative lymphomagenic potential of HHV-8 and EBV and their co-existence in African KS lesions, tumor-infil trating lymphocytes in these cases do not show evidence of clonal expansion that might be an early manifestation of lymphoma. Nevertheless, these stud ies are a case in point that sparse lymphoid subpopulations in lesional and uninvolved extranodal tissues can give rise to restricted clonal patterns that must be interpreted carefully to avoid the misdiagnosis of occult lymp homa.