Kaposi's sarcoma in renal transplant recipients

Kaposi's sarcoma (KS) is a spindle-shaped vascular cell tumor that occurs in the skin, lymphoid, respiratory and gastrointestinal tissues. It may resemble aggressive malignant neoplasm in HIV-related or in post-transplant types but classic form may behave as benign, potentially controllable and reversible hyperplasia. KS lesions from the onset are dispersed and multicentric. KS probability increases in solid organ transplant recipients (approximately 3/1000 patients). KS occurrence is associated with: type and dose of immunosuppression, chronic stimulation by foreign allograft antigens, viral infections (Herpes virus 8), anti rejection and induction therapy, etc. 90% of KS cases appear as dark blue or purplish macular lesions that may form nodular tumors. Histological picture shows networks of spindle shaped cells and vascular spaces surrounded by an endothelial cell layer. There is no uniform schema of KS treatment in renal transplant recipients. Immunosuppression must be reduced to the lowest levels which preserve allograft function. CsA should be converted to mofetil mycophenolate or mTOR-inhibitors. After conversion to MMF regression of KS was observed, although low therapeutic MMF doses seem to be appropriate. Sirolimus seems to inhibit the growth of established vascularized tumors and this effect is best realized with relatively low immunosuppressive doses of drug.