To discuss the utility of 
IRPF patients diagnosed between September 2011 and June 2016 were included. Retroperitoneal malignancy patients were included as control. The morphological features and FDG uptake of retroperitoneal lesions were measured along with lymph node (LN) mapping.
Seventy-one iRPF patients were included. Fifteen lymphoma patients and 6 retroperitoneal metastatic malignancy patients were included as control. Significant differences in morphological features were observed between iRPF and lymphoma but not retroperitoneal metastatic carcinoma. Compared with malignancy, iRPF displayed a lower frequency of high-FDG-uptake retroperitoneal lesions (P = 0.017) and a lower mean maximum standardized uptake value (SUV
Retroperitoneal malignancy can mimic iRPF morphologically. 