You are in: eMedicine Specialties > Radiology > MUSCULOSKELETAL Osteosarcoma, VariantsArticle Last Updated: May 21, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Geoff Hide, MBBS, MRCP, FRCR, Consultant Musculoskeletal Radiologist, Department of Radiology, Freeman Hospital; Honorary Clinical Lecturer, Faculty of Medical Sciences, University of Newcastle upon Tyne Geoff Hide is a member of the following medical societies: British Medical Association, Royal College of Physicians, and Royal College of Radiologists Editors: Amilcare Gentili, MD, Clinical Professor of Radiology, University of California at San Diego; Consulting Staff, Department of Radiology, Thornton Hospital; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Murali Sundaram, MBBS, FRCR, FACR, Consulting Staff, Department of Diagnostic Radiology, The Cleveland Clinic Foundation; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Felix S Chew, MD, MBA, EdM, Professor, Department of Radiology, Vice Chairman for Radiology Informatics, Section Head of Musculoskeletal Radiology, University of Washington Author and Editor Disclosure Synonyms and related keywords: primary malignant tumor of bone, bone tumor, bone malignancy INTRODUCTIONSection 2 of 12
  BackgroundOsteosarcoma is the most common primary malignant tumor of bone, excluding plasma cell myeloma. Approximately 75% of all osteosarcomas are of the classic or conventional type, and the remaining 25% comprise the osteosarcoma variants, which are the subject of this article.1 The variants are a heterogeneous group of osteosarcomas with a range of different imaging and behavioral features. PathophysiologyOsteosarcoma is a malignant mesenchymal sarcoma characterized by the direct formation of bone or osteoid by tumor cells. For further information on the individual pathologic characteristics of the osteosarcoma variants, the reader is directed to the References section. FrequencyUnited StatesThe peak incidence of osteosarcoma occurs in the second decade of life, which corresponds to the maximal period of skeletal growth. The incidence of osteosarcoma in persons younger than 20 years is 4.8 cases per million population. Approximately 75% of these cases are conventional osteosarcomas. Frequency data for the individual osteosarcoma variants is difficult to calculate because many are rare tumors. The table below shows the relative percentages of the osteosarcoma variants.1, 2 Frequency of osteosarcoma variants in the United States
Mortality/MorbidityThe overall prognosis for patients with osteosarcoma depends on the stage of the tumor at presentation. Without metastases, long-term survival is in the order of 60-85%.
RaceOsteosarcoma occurs in all racial and ethnic groups, but its frequency is slightly greater in African Americans than in Caucasians. SexMost variants have a sex distribution similar to that of conventional osteosarcoma. That is, they are slightly more common in males than in females. Gnathic osteosarcoma and intraosseous low-grade osteosarcoma are believed to show a more equal sex distribution, and some studies of parosteal osteosarcoma have suggested that the tumor is more prevalent in females. AgeConventional osteosarcoma has a wide age range, with a peak in the second decade. This peak is thought to be associated with the period of maximal intensity of skeletal growth.
AnatomyConventional osteosarcoma is most frequent in areas of high skeletal growth, especially the metaphyseal regions of the distal femur, proximal tibia, and proximal humerus. Most osteosarcoma variants follow a similar distribution, with the exception of gnathic (mandible and maxilla) lesions, intracortical lesions (rare but more typically diaphyseal), periosteal lesions (more typically diaphyseal), and secondary osteosarcomas. The last osteosarcomas frequently occur in the pelvis and proximal femur, often in association with Paget disease. Clinical DetailsMost osteosarcoma variants have presentations similar to that of a conventional osteosarcoma, with pain, swelling, and a palpable mass that may have been present for weeks or months. Parosteal osteosarcoma is notable for the presence of a mass that in some cases may have been present for years. Intraosseous low-grade tumors may have a presentation that is similarly prolonged. Multicentric osteosarcoma may result from 1 of 2 processes. Multiple primary tumors may occur either synchronously or asynchronously. Alternatively, multicentric disease may occur from a single primary lesion with metastases to other skeletal sites at presentation. Regardless of controversies over which mechanism is more likely, when multicentric disease is initially present, the prognosis is poor. Preferred ExaminationPreferred modalities for evaluating primary disease are radiography, magnetic resonance imaging (MRI), and sometimes computed tomography (CT) scanning. Staging is always performed by using chest CT scanning to detect pulmonary metastases. Isotopic bone scanning is generally used to detect skeletal metastases or synchronous tumors, but whole-body MRI may replace this study. DIFFERENTIALSSection 3 of 12
Aneurysmal Bone Cyst Chondroblastoma Chondromyxoid Fibroma Chondrosarcoma Giant Cell Tumor Malignant Fibrous Histiocytoma, Soft Tissue Osteoblastoma Osteochondroma and Osteochondromatosis Stress Fracture Other Problems to Be ConsideredOsteochondroma (parosteal osteosarcoma)
Langerhans cell histiocytosis Infection Rhabdomyosarcoma RADIOGRAPHSection 4 of 12
FindingsTelangiectatic osteosarcoma is generally lytic, with a periosteal reaction and soft-tissue mass. When the tumor margins are well defined, it may mimic an aneurysmal bone cyst. Small-cell osteosarcoma appears similar to a conventional osteosarcoma; it often has mixed areas of sclerosis and lysis. Intraosseous low-grade osteosarcoma may be lytic, sclerotic, or mixed; it often has deceptively benign features of well-defined margins and the absence of periosteal changes or a soft-tissue mass. Gnathic tumors may be lytic, sclerotic, or mixed, and bone destruction, periosteal reaction, and soft-tissue extension are common. Intracortical osteosarcomas are described as radiolucent and geographic, and they contain a small amount of internal mineralization. High-grade surface osteosarcomas are shown as broad-based soft-tissue masses with varying degrees of mineralization arising from the surface of the bone. Parosteal osteosarcomas are typically densely ossified tumors arising from a broad base on the adjacent bone. Unlike osteochondromas, parosteal osteosarcomas involve no continuation of the medullary cavity into the tumor. CT SCANSection 5 of 12
FindingsCT scanning is helpful in the evaluation of a variety of the osteosarcoma variants. It may demonstrate fluid levels in telangiectatic osteosarcoma, and a contrast-enhanced CT scan can be helpful in discriminating such a lesion from an aneurysmal bone cyst. Telangiectatic osteosarcoma differs from an aneurysmal bone cyst in that the former has a rim of tumor cells that surrounds the cystic spaces. This tissue rim shows typically nodular enhancement after the intravenous administration of contrast material. CT scanning is useful in the evaluation of bone changes occurring in areas of complex anatomy. Examples are the changes in the maxilla or mandible that are associated with gnathic osteosarcoma and those in the pelvis that are associated with secondary osteosarcoma. CT scanning provides useful information about the surface osteosarcoma variants, including parosteal, periosteal, and surface high-grade tumors. When appropriate and performed in consultation with an orthopedic oncologist, CT scanning can be useful in guiding biopsy. MRISection 6 of 12
FindingsMRI is the optimum technique for local staging of osteosarcomas. In certain cases, MRI is combined with CT scanning. MRI accurately demonstrates the extent of a tumor within bone and soft tissue. At least 1 sequence, either a T1-weighted or a short-tau inversion recovery (STIR) sequence, should be performed to image the entire bone. This is necessary to exclude skip lesions that are present within the same bone but are distant from the primary lesion. Periosteal osteosarcoma is typically a chondroblastic lesion, and the tumor usually has high signal intensity on T2-weighted MRIs. Degree of ConfidenceMRI is more sensitive than CT scanning in demonstrating fluid-fluid levels in telangiectatic osteosarcoma because of its greater intrinsic soft-tissue contrast. False Positives/NegativesFluid-fluid levels can be seen in benign bone lesions as well, particularly aneurysmal bone cysts. ULTRASOUNDSection 7 of 12
FindingsUltrasonography can demonstrate the soft-tissue extent of the tumor, but it cannot be used to evaluate the intramedullary component of the lesion. Ultrasonography is not routinely used in staging such lesions. Sonography can be useful in guiding percutaneous biopsy of the soft-tissue component of the tumor, again in consultation with an orthopedic oncologist. NUCLEAR MEDICINESection 8 of 12
FindingsOsteosarcomas typically show increased uptake of radioisotope; this characteristic makes bone scans sensitive but not specific. Bone scans are most useful in excluding multifocal disease. Multiple-gated acquisition (MUGA) cardiac scans may be required to monitor the toxic effects of certain chemotherapeutic agents. ANGIOGRAPHYSection 9 of 12
FindingsAngiography is no longer used in the staging of osteosarcoma. INTERVENTIONSection 10 of 12
Histologic confirmation of the nature of the tumor is initially required; the analysis should be performed after MRI and in consultation with the tumor surgeon. Biopsy must be performed after the MRI study because hemorrhage occurring at the time of biopsy alters the signal intensity characteristics of the tumor at subsequent MRI examinations. The site of the biopsy track must be planned to prevent contaminating the muscle compartments that the surgeon would not otherwise excise. The biopsy track is removed during surgery, and consideration should be given to marking the track with suture material or dye if there will be a delay between biopsy and formal excision. Tumors are often densely sclerotic and difficult to examine with percutaneous biopsy, but the associated soft-tissue component is often amenable to sonography-guided biopsy. Treatment is geared around surgery, with limb salvage when possible. Presurgical chemotherapy is used. The response to chemotherapy is assessed in the resected specimen or by means of pre-resection biopsy. The response is considered good when tumor necrosis is greater than 90%. This necrosis is a predictor of a successful outcome. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
Osteosarcoma, Variants excerpt Article Last Updated: May 21, 2007 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
