We have established a non-metastatic and a metastatic human Kaposi sarcoma (KS) xenograft model in SCID mice by injecting KS-Imm cells subcutaneously and intrasplenically, respectively. KS-Imm cells expressed endothelial markers, CD34 and vWF in vivo. Furthermore, we have shown that these cells express all the splice variants of the WT1 gene and WT1wt protein in vitro and in vivo detected by nested PCR and immunohistochemistry. WT1 expression in the peripheral blood was only detectable in case of metastatic KS model suggesting it as a molecular marker of progression.