Interesting ImagesGiant Cell Tumor With Atypical Imaging Implying OsteosarcomaAriga, Akane MD∗; Kanda, Hiroaki MD, PhD†; Ando, Yoshiaki MD∗; Gokita, Tabu MD∗Author Information From the Departments of ∗Orthopaedic Surgery †Pathology, Saitama Cancer Center, Saitama, Japan. Received for publication April 4, 2020; revision accepted May 30, 2020. Conflicts of interest and sources of funding: none declared. Correspondence to: Akane Ariga, MD, Saitama Cancer Center, 780 Komuro, Ina, Kita-adachi-gun, Saitama 362-0806, Japan. E-mail: [email protected]. Clinical Nuclear Medicine: November 2020 - Volume 45 - Issue 11 - p 892-893 doi: 10.1097/RLU.0000000000003226 Buy Metrics Abstract Giant cell tumor (GCT) of bone is benign and typically shows osteolytic changes on x-ray, whereas osteosarcoma is malignant and generally shows osteolytic and osteoblastic mixed images. We experienced a rare case of GCT with atypical radiological findings. The tumor found in the right knee of a 15-year-old girl comprised a wide range of osteoblastic and osteolytic lesion in medial femur. Technetium uptake, however, was detected only in osteoblastic part, and immunohistochemical staining of biopsy showed diffusely positive for antihistone G34W and almost negative for Ki-67. These results strongly suggest the tumor was GCT. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.