Posttransplant lymphoproliferative disease in a pediatric patient as seen on PET/CT scan

We present a case of an 18-year-old who had received a renal transplant 4 years ago. He underwent an ultrasound due to pain and fullness in right flank that showed hydronephrosis of the transplant kidney. A percutaneous nephrostomy was performed for hydronephrosis of the transplant kidney because of a new mass in the pelvis as seen on CT scan. This mass was F-18 FDG avid on a PET scan. A biopsy confirmed the diagnosis of posttransplant lymphoproliferative disease. The patient responded to treatment. A follow-up PET scan showed resolution of this mass. PET proved helpful in making the diagnosis and follow-up of the patient.