49 Radionuclide Bone Scanning of Osteosarcoma: Falsely Extended Uptake Patterns Felix S. Chew1’ 2 Terry M. Hudson1 Received November 1 3, 1 981 : accepted after revision March 24, 1982 1 Department of Radiology, University of Florida, J. Hillis Miller Health Center, Gainesville, FL 32610. Address reprint requests to T. M. Hudson (Box J-374). 2Present address: Third General Dispensary, APO New York, NY 90164. AJR 139:49-54, July 1982 0361 -803X/82/ 1391 -0049 $00.00 © American Roentgen Ray Society The pathologic specimens of 18 osteosarcomas of long bones were examined to correlate histologic abnormalities with abnormalities seen on preoperative mTc pyre- phosphate or methylene diphosphonate bone scans. Seven scans accurately repre- sented the extent of the tumors. Eleven scans disclosed increased activity extending beyond the radiographic abnormalities. In eight of these, there was no occult tumor extension and in the other three, the scan activity did not accurately portray the skip metastases that were present. Therefore, these 11 scans demonstrated the falsely extended pattern of uptake beyond the true limits of the tumors. Pathologic slides were available for 10 of the 11 areas of bone that exhibited extended uptake. In two instances, there was no pathologic abnormality. In the other eight cases we found marrow hyperemia, medullary reactive bone, or periosteal new bone. This is the first description of these histologic abnormalities of medullary bone in areas of extended uptake on radionuclide bone scans. Radionuclide bone scans of primary bone tumors offer three potentially useful items of information: (1 ) a demonstration of uptake of the radiopharmaceutical within the lesion itself, (2) an indication of the anatomic extent of the lesion, and (3) detection of the presence and location of other skeletal lesions. In osteosar- comas, there is invariably intense uptake of the tracer by the tumor itself, related to the abundant osteoblastic activity and profuse hypervascularity usually asso- ciated with these tumors. This increased uptake within the tumor has little clinical usefulness, since the lesion is already apparent on plain radiographs. The primary mode of treatment of osteosarcomas is surgical, either amputation or extensive local resection, although radiation therapy and chemotherapy may also be used [1 -3]. Knowledge of the exact anatomic extent of the tumor can have considerable influence on treatment planning [4, 5]. Goldman et al. [6] showed a close correlation between uptake on the radionuclide bone scan, the plain radiograph, and gross pathology with respect to tumor extent. However, they and others have also emphasized the difficulties in interpretation caused by the ‘ ‘ extended pattern of uptake’ ‘ of radiopharmaceutical beyond the true margin of the bone lesions [7-1 3]. Hypothesized mechanisms for extended uptake include disuse osteoporosis and regional hyperemia [8, 9]. In the past, bone scanning was not very useful for the detection of multiple bone lesions in osteosarcoma because multicentric osteosarcoma is rare, and bone metastases from a solitary tumor rarely appeared before radiologically obvious pulmonary metastases. However, the introduction of adjuvant chemo- therapy has changed the course of the disease. In a recent study, 1 5% of osteosarcoma patients receiving chemotherapy developed bone metastases without evidence of lung metastases [1 4]. Therefore, serial bone scanning is useful during follow-up of these patients, but the bone scan is unlikely to reveal skeletal metastases in patients who have not received chemotherapy, unless lung metastases are already present [14]. Downloaded from www.ajronline.org by 52.73.204.196 on 05/16/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved