Interesting ImagesRenal Pelvis Involvement of Immunoglobulin G4–Related Disease Mimicking Malignancy on 18F-FDG PET/CTJiang, Yuanyuan MD; Hou, Guozhu MD; Cheng, Wuying MDAuthor Information From the Department of Nuclear Medicine, Peking Union Medical College Hospital Chinese Academy of Medical Sciences and Peking Union Medical College; and Beijing Key Laboratory of Molecular Targeted Diagnosis and Therapy in Nuclear Medicine, Beijing, China. Received for publication March 15, 2019; revision accepted March 31, 2019. Conflicts of interest and sources of funding: This work is supported by the National Natural Science Foundation of China (no. 81371588, no. 81101074). None declared to all authors. Correspondence to: Wuying Cheng, MD, Department of Nuclear Medicine, Peking Union Medical College Hospital, No. 1 Shuaifuyuan, Wangfujing, Dongcheng District, Beijing 100730, China. E-mail: [email protected]. Clinical Nuclear Medicine: September 2019 - Volume 44 - Issue 9 - p 767-768 doi: 10.1097/RLU.0000000000002621 Buy Metrics Abstract A 70-year-old woman with bilateral submandibular gland enlargement was referred to our hospital. Submandibular gland biopsy indicated immunoglobulin G4 (IgG4)–related disease (IgG4-RD) involvement. Contrast-enhanced CT was undergone for evaluation of IgG4-RD and revealed a mass located at the left renal pelvis. 18F-FDG PET/CT showed bilateral FDG-avid submandibular gland and a hypermetabolic mass in the left renal pelvis. The lesions were decreased in both size and metabolism on follow-up PET/CT 2 months after treatment with prednisone. This case illustrated a rare site for IgG4-RD, and the renal pelvis involvement should be considered into differential diagnosis in patients with IgG4-RD history. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.