Abstract
A 52-year-old male had pain in the right back and right hypochondrium, and an abdominal CT scan revealed a 49-mm tumor in the right upper perirenal space. Additional MRI and PET-CT suggested that the tumor may be a primary adrenal carcinoma and could invade the liver and diaphragmatic leg. The tumor was completely removed by laparotomy and histopathologically diagnosed as retroperitoneal primary undifferentiated pleomorphic sarcoma. The patient has remained recurrence-free for 1.5 years after the surgery.