Interesting ImagesMediastinal 99mTc-Methylene Diphosphonate Accumulation in a Patient With Primary Mediastinal Soft Tissue Giant Cell TumorChen, Haotian MD; Fan, Qiuping MD; Su, Minggang MDAuthor Information From the Department of Nuclear Medicine, West China Hospital, Sichuan University, Chengdu, China. Received for publication January 13, 2020; revision accepted February 19, 2020. H.C. and Q.F. contributed equally to this work. Conflicts of interest and sources of funding: This study was supported by the Key Projects of the Ministry of Science and Technology (grant 2017YFC0113304). None declared to all authors. Correspondence to: Minggang Su, MD, Department of Nuclear Medicine, West China Hospital, Sichuan University, #37 Guo Xue Lane, Chengdu 610041, China. E-mail: email@example.com. Clinical Nuclear Medicine: June 2020 - Volume 45 - Issue 6 - p 477-479 doi: 10.1097/RLU.0000000000003037 Buy Metrics Abstract Soft tissue giant cell tumor (GCT) is rare. It usually involves the extremities. We report the case of a 37-year-old woman who was suspected of having mediastinal tumor on radiograph. Thoracic CT revealed the tumor had extensive calcification and invaded the adjacent vertebrae and spinal canal. It intensively accumulated 99mTc-methylene diphosphonate on bone scan. The tumor showed hypointensity on T1-weighted and mixed intensity on T2-weighted fat-saturated sagittal images. Finally, a soft tissue GCT was confirmed by pathology. The case cautions us soft tissue GCT should be in the differential diagnosis spectrum in a calcified posterior mediastinal mass with 99mTc-methylene diphosphonate accumulation. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.