Background: This retrospective single-center study was undertaken to assess the occurrence of de novo neoplasms in renal transplant recipients according to the immunosuppressive regimen and time after transplantation.
Material/Methods: Observation encompassed 1028 patients transplanted between the years 1983–2006 and followed for 0.5–23 years. Patients with skin cancer other than melanoma were excluded due to incomplete data collection.
Results: Malignancy appeared in 4.8% (49) of the patients after the period of 5.8±4.7 years at the age of 54±13 years. The most common malignancies were urinary tract tumors (22%) and non-Hodgkin lymphoma with post-transplant lymphoproliferative disease (PTLD) (16%). Malignancy occurred in 5.2% of patients on cyclosporine (CSA), azathioprine (AZA) and prednisone (P); in 3.4% of patients on mofetil mycophenolate (MMF) with CSA and P; in 3.3% of patients on MMF with tacrolimus (TAC) and P; and in 2 of 20 patients (10%) receiving AZA with P 15 years after transplantation. The regimen consisting of CSA, AZA with P could be distinguished by the higher risk of malignancy occurrence. The occurrence of malignancy was significantly earlier on MMF+TAC+P compared to other regimens (p<0.05). The highest incidence of malignancy on AZA with P could be attributed to the longer observation period.
Conclusions: In the new era of immunosuppression, despite lower occurrence, malignancy tends to appear earlier after the transplantation.

Keywords: Malignancy, Kidney Transplantation, immunosuppression