Malignancy after solid organ transplantation: Comprehensive imaging review

Life expectancies for solid organ recipients as well as graft survival rates for these patients have improved over the years because of advanced immunosuppressive therapies; however, with chronic use of these drugs, posttransplant malignancy has become one of the leading causes of morbidity for them. The risk of carcinogenesis in transplant recipients is significantly higher than for the general population and cancers tend to manifest at an advanced stage. Posttransplant malignancies are thought to develop by three mechanisms: de novo development, donor-related transmission, and recurrence of a recipient’s pretransplant malignancy. Although nonmelanoma skin cancer, Kaposi sarcoma, posttransplant lymphoproliferative disorder, anogenital cancer, and lung cancer are malignancies that are thought to arise de novo, malignant melanoma and cancers that arise in the renal allograft are frequently donor related. Hepatocellular carcinomas and cholangiocarcinomas have a greater tendency to recur in liver transplant recipients. An altered or deranged immune system caused by chronic immunosuppression is considered to be one of the major contributing factors to carcinogenesis. The proposed pathogenic mechanisms for oncogenesis include impaired immunosurveillance of neoplastic cells, weakened immune activity against oncogenic viruses, and direct carcinogenic effects of immunosuppressive agents. Imaging plays an important role in screening, follow-up, and long-term surveillance in patients with malignancies because key imaging features can guide in their timely diagnosis. However, some benign entities such as transplant-related renal fibrosis, biliary necrosis, and infectious nodules in the lungs mimic malignancies and require pathologic confirmation. Management strategies that can improve malignancy-related morbidity and mortality in transplant recipients include prevention of risk factors, appropriate modulation of immunosuppressive agents, prophylaxis against infection-related malignancies, and use of intensive targeted screening programs.