Donor-Derived Renal Cell Carcinoma in a Kidney Allograft: A Case Report.

Renal cell carcinoma (RCC) in the kidney allograft is a relatively rare complication most commonly seen approximately a decade or more after transplant. We report a case of diffuse multifocal RCC within 6 months of transplant. The initial signal leading to an abnormality in the graft was an elevated routine cell-free DNA. Initial imaging findings appeared consistent with post-transplant lymphoproliferative disorder; however, biopsy would ultimately yield RCC. The patient's diffuse disease necessitated radical nephrectomy. Tumor DNA fingerprinting was employed in this case to show the tumor originated from donor tissue rather than host, indicating primary rather than metastatic disease. Early RCC is a rare complication. Most cases are detected at an early stage, likely as a result of increased surveillance with ultrasound imaging. A donor's social history including significant tobacco use should be considered when evaluating the risk of malignancy transmission in the allograft. Clinicians should be aware of multifocal RCC as a potential differential diagnosis for diffuse nodular infiltrates in the allograft.