J Korean Bone Joint Tumor Soc JKBJTS The Journal of the Korean Bone and Joint Tumor Society 1226-4962 2233-9841 The Korean Bone & Joint Tumor Society 10.5292/jkbjts.2012.18.1.45 Case Report FDG-PET/CT Complements Bone Scan with Respect to the Detection of Skip Metastasis of Osteosarcoma: A Case Report Cheon Gi Jeong M.D. * Choe Jae Gol M.D. * Chae In Jung M.D. Lee Dae Hee M.D. Song Sang Heon M.D. Kim Myo Jong M.D. Park Jong Hoon M.D. Department of Orthopedic Surgery, Korea University Hospital, Seoul, Korea. Department of Nuclear Medicine, Korea University Hospital, Seoul, Korea. Correspondence to: Jong Hoon Park, M.D. Department of Orthopedic Surgery, Korea University Hospital, 126-1, Anamdong 5-ga, Seongbuk-gu, Seoul 136-705, Korea. TEL: +82-2-920-6609, FAX: +82-2-924-2471, pjh1964@hanmail.net 06 2012 27 06 2012 18 1 45 49 02 03 2012 28 05 2012 30 05 2012 Copyright © 2012 by The Korean Bone and Joint Tumor Society 2012

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Skip lesion is not uncommon feature in osteosarcoma and considered to be importantly associated with poor prognosis factor, and thus, should be excised with the main mass. The accurate pre-operative evaluation of the intramedullary extent of osteosarcoma is essential, because it determines the level of bone resection. Among the reliable detection methods, bone scan has a drawback of high rate of false negative results and regional MRI has a difficulty to cover the whole involved lesions without clinical suspicion. The authors report a case of osteosarcoma of the distal femur with a proximal skip lesion that was not detected by either regional MR imaging or by bone scan, but which was visualized by FDG-PET/CT.

 skip metastasis osteosarcoma F-18 FDG-PET/CT bone scintigraphy (BS) Enneking WF Kagan A "Skip" metastases in osteosarcoma Cancer 1975 36 2192 2205 Enneking WF Kagan A The implications of "skip" metastases in osteosarcoma Clin Orthop Relat Res 1975 111 33 41 Wuisman P Enneking WF Prognosis for patients who have osteosarcoma with skip metastasis J Bone Joint Surg Am 1990 72 60 68 Cheon GJ Chung JK Kim YK Comparasion of whole body F-18 FDG PET and Tc-99m MDP bone scan for the assessment of metastatic bone lesions World J Nucl Med 2003 2 18 29 Gosheger G Gebert C Ahrens H Streitbuerger A Winkelmann W Hardes J Endoprosthetic reconstruction in 250 patients with sarcoma Clin Orthop Relat Res 2006 450 164 171 Grimer RJ Surgical options for children with osteosarcoma Lancet Oncol 2005 6 85 92 Ardran GM Bone destruction not demonstrable by radiography Br J Radiol 1951 24 107 109 Berquist TH Magnetic resonance imaging of primary skeletal neoplasms Radiol Clin North Am 1993 31 411 424 Basu S Alavi A Bone marrow and not bone is the primary site for skeletal metastasis: critical role of [18F]fluorodeoxyglucose positron emission tomography in this setting J Clin Oncol 2007 25 1297 author reply 1297-9 Hur J Yoon CS Ryu YH Yun MJ Suh JS Accuracy of fluorodeoxyglucose-positron emission tomography for diagnosis of single bone metastasis: comparison with bone scintigraphy J Comput Assist Tomogr 2007 31 812 819

Plain radiographs show an osteolytic lesion of a medial aspect of distal femur in AP view.

Coronal and sagittal T1-weighted MR image at presentation show an osteosarcoma extending approximately 10 cm from the distal femoral articular surface. There is some soft tissue extension in medial direction.

Whole body bone scan at presentation showing isolated area of increased uptake in medial aspect of right distal femur. There is no suspected metastatic and skip lesion.

MR imaging of Right femur at the time of pre-operative restaging examination. T1 coronal and sagittal image of whole femur showing the skip lesion in proximal diaphysis.

Plain femur AP and Lat view showing no significant skip lesion of the proximal diaphysis.

Initial FDG-PET scan and restaging PET scan also showing distinct skip lesion.