Extraskeletal osteosarcoma: spectrum of imaging findings

OBJECTIVE: The purpose of this article is to present the spectrum of imaging findings of primary and metastatic extraskeletal osteosarcoma and highlight the differences from primary osteogenic osteosarcoma in bone. CONCLUSION: Extraskeletal osteosarcoma is a rare mesenchymal malignancy of soft tissue, histologically indistinguishable from primary osteosarcoma of bone. However, there are distinct differences in demographics, imaging features, prognosis, and management compared with osteogenic osteosarcoma. Imaging characteristics reflect tumor morphology, with only 50% of primary tumors showing mineralization. Metastases may or may not show mineralization, even if present in the primary tumor. The overall prognosis is poor.     

Bone Tumors Occurring in the Soft Tissues: A Review of the Clinical,Imaging, and Histopathologic Findings

Although rare in everyday practice, malignancies that classically arise from bone or cartilage have been reported to arise de novo in various soft tissues in the body, resulting in a diagnostic challenge for the clinician, radiologist, and pathologist.Differential diagnoses of bone tumors often depend on anatomic location of the lesion. For example, the classic location of osteosarcoma is in the metaphysis of long bones about the knee. Histologically osteosarcoma is characterized by tumor cells that directly produce osteoid, bone, or cartilaginous matrix. In extraskeletal osteosarcoma, the clinical and radiologic picture is very different from a conventional osteosarcoma. They occur in older patients, present as a soft tissue mass often coincidentally following trauma and have a worse prognosis. The imaging characteristics are often nonspecific with mineralized elements in a well-defined soft tissue mass. The mineralized elements may or may not be visible. Magnetic Resonance sequences demonstrate a well circumscribed soft tissue mass with hemorrhagic and enhancing solid components. The pathologic features of extraskeletal osteosarcoma on a microscopic scale are identical to that of skeletal lesions. Likewise, conventional chondrosarcomas present in older patients with a growing, painful soft tissue prominence most commonly involving the long tubular bones. In extraskeletal chondrosarcoma however, the presentation is in somewhat younger patients with a painful soft tissue prominence typically in the head (meninges), neck, or upper leg. The pathologic features are most often that of a myxoid chondrosarcoma which is characterized by strands of small cells over a myxoid matrix. Imaging features include chondroid matrix, heterogenous contrast enhancement, and amorphous internal calcification on Computed Tomography. On Magnetic Resonance sequences the matrix has a low signal on all sequences, and variable inhomogeneity depending on grade of the lesion. Other extraskeletal bone tumors include Ewing's sarcoma and osteoid osteoma amongst other lesions.Although these malignancies may be rare clinical entities, they often exhibit characteristic clinical, imaging, and histopathological findings although differing in treatment and prognosis. Knowledge of these and other common mimicking lesions will help guide the clinician and radiologist to make an accurate diagnosis.     

Extraskeletal osteosarcoma of the jaw

Extraskeletal osteosarcoma is a rare malignancy, which accounts for 1–2% of all soft tissue sarcomas; occurrence of these tumors in the head and neck is extremely rare. We present a case of extraskeletal osteosarcoma arising in the subcutaneous tissue of the jaw angle, the central portion of which displayed calcification. Imaging findings were interesting in terms of a high grade malignancy in that the tumor was small and well circumscribed; its appearance mimicked a calcified lymph node. The differential diagnosis of this lesion as well as the imaging and pathological features of extraskeletal osteosarcoma are discussed.     

Unusual Presentation of Widely Metastatic Extraskeletal Osteosarcoma: Case Report

Extraskeletal osteosarcoma is a highly aggressive malignant osteoid forming mesenchymal neoplasm arising from soft tissues which accounts for 1% of all soft tissue sarcomas. We report the case of a 46-year-old female with no significant past medical history presenting to an emergency department with a right lateral thigh mass following minor trauma. She was eventually found to have high grade extraskeletal osteosarcoma with rapid progression of disease resulting in patient demise. Differentiation of these lesions from alternative processes relies on specific imaging and pathologic features. Differential diagnoses include both benign and malignant etiologies such as myositis ossificans, soft tissue hemangiomas, and other malignant soft tissue neoplasms such as epithelial and synovial sarcoma.     

Extraskeletal osteosarcoma arising in myositis ossificans

A 53-year-old woman had extraskeletal osteosarcoma that developed from a soft tissue bony mass present on the volar aspect of the left wrist for 4 years. Initially, the bony mass was soft and movable, but during the first year it became hard and fixed. The patient had no history of trauma. Because the lesion did not grow or cause any symptoms, the patient did not come to the hospital until 4 years after she first noticed the lesion. Radiologically, the bony mass had features characteristic of mature myositis ossificans, showing ”eggshell” ossification. A nonmineralized soft tissue mass occurred between the surface of the radius and the bony shell. Histologically, a high-grade osteosarcoma was present between the surface of the radius and the well-differentiated bone tissue, which included fatty and hematopoietic marrow. All the findings indicated that our patient had an extremely rare case of malignant transformation of myositis ossificans. Received: 22 June 2000 Revision requested: 2 August 2000 Revision received: 14 September 2000 Accepted: 25 September 2000     

继发性骨肉瘤的临床特点及影像学表现

目的:分析继发性骨肉瘤的临床特点及影像学表现.方法:回顾性分析经手术病理证实的25例继发性骨肉瘤患者的病例资料.25例均行X线及CT检查(5例行增强CT),16例行MRI增强检查.结果:本组患者的中位年龄45岁(14～76岁),中位恶变时间为8年(0.5～18.0年).25例中骨纤维结构不良、骨母细胞瘤等良性肿瘤或肿瘤样病变恶变12例,表现为溶骨性破坏、软组织肿块形成及病灶迅速增大等与原发骨肉瘤相仿的影像学改变;骨巨细胞瘤植骨后恶变继发性骨肉瘤8例、金属植入相关的继发性骨肉瘤2例,均表现为移植骨吸收、周围出现明显软组织肿块及肿瘤骨形成;放疗后继发性骨肉瘤2例,以成骨性骨质破坏为主;Paget病继发性骨肉瘤1例,表现为在患骨增粗、不规则变形基础上,出现溶骨性破坏及软组织肿块.病理结果:镜下有不同程度的细胞异形性、肿瘤骨形成.所有病例术后随访时间为1.5～12.0年(平均3.4年),8例出现肺部转移.结论:病理组织学上继发性骨肉瘤与原发性骨肉瘤无明显差异,但结合其临床资料及影像学表现可明确诊断.     

A low-grade extraskeletal osteosarcoma

The case of a 35-year-old woman with low-grade extraskeletal osteosarcoma of the left leg is presented. Radiographs showed peripheral ossification of the lesion, suggesting myositis ossificans. Most of the tumor was composed of cartilage, and the cellularity and cell atypia of the proliferating chondrocytes were mild to moderate. In the periphery, bone formation with a relatively clear margin and proliferation of spindle cells with minimal nuclear atypia were observed. The average percentage of cells positive for MIB-1 was 9.0%. A diagnosis of low-grade extraskeletal osteosarcoma was made on the basis of these histologic findings. The clinical course 47 months after a wide excision was uneventful.     

骨肉瘤的CT征象

目的 总结骨肉瘤的ＣＴ征象及其特点。方法 分析４０例经手术病理证实的骨肉瘤的ＣＴ,Ｘ线平片征象和病理切片,３２例平扫,８例平扫后行增强扫描,病理检查４０例,其中病理大切片９例,结果 骨肉瘤的基本征象有骨质破坏,肿瘤骨形成,骨膜反应及软组织肿块,这些征象在平片,ＣＴ上均可见到,但两者的表现有所不同,ＣＴ还可显示平片不可或难以发现的征象,肿瘤与周围软组织的分界,肿瘤坏死,出血,肿瘤侵犯关节及跳跃性病灶     

长骨骨干骨肉瘤X线、CT及MRI表现

目的 分析长骨骨干骨肉瘤X线、CT和MRI表现,探讨有关的临床特点和鉴别诊断.方法 28例长骨骨干骨肉瘤患者,均经手术与病理证实,其中病变位于股骨干18例、腓骨干4例、肱骨干4例、胫骨干2例.所有患者均行X线、CT和MR检查,对其影像学表现与手术病理结果进行对照,并由双盲法分析确认.结果 28例中,X线和CT显示广泛骨质破坏16例,骨膜反应22例.X线显示软组织肿块18例,肿瘤骨和瘤样钙化12例.CT平扫显示软组织肿块22例,增强扫描显示软组织肿块24例,肿瘤骨和瘤样钙化16例.MRI显示骨质破坏和骨膜反应10例,软组织肿块26例,其周围可见软组织水肿及骨髓水肿.骨膜反应在SE T1WI上呈等低信号,T2WI呈等信号.软组织肿块在T1WI为等信号,T2WI及STIR呈等高信号.软组织水肿及骨髓水肿在T2WI及STIR呈高信号.MRI增强检查显示病灶均呈不均匀强化,骨髓水肿和软组织肿块均见强化.结论 X线、CT和MRI从不同方面反映长骨骨干骨肉瘤的影像病理特点,其发病率低,骨破坏范围大,无病理性骨折.成骨型骨干骨肉瘤较易诊断,溶骨型应与Ewing瘤、恶性巨细胞瘤等鉴别.

Abstract：

Objective To explore the findings of diaphysial osteosarcoma in long bone on X-ray,CT and MRI, and discuss their clinical features and manifestations for differential diagnosis. Methods Twenty-eight cases with diaphysial osteosarcoma in long bone proved by surgery and pathology were reviewed retrospectively. Eighteen tumors were located in the femur, 4 in fibula, 4 in humerus and 2 in tibia. All of the patients were examined by X-ray, CT and MRI. The imaging manifestations on X-ray, CT and MRI were analyzed, and the relationship of the imaging features with the pathological types was also observed. The imaging signs were correlated with the pathologic findings with a double blind method. Results Of the 28 cases, there were 16 cases with large bone destruction, 22 cases with periosteal reaction on X-ray and CT. On X-ray, 18 cases showed soft tissue mass and 12 cases with neoplastic bone and tumor calcification.While on CT, 22 cases showed soft tissue mass on plain scan and 2 more cases displayed soft tissue mass after the injection of contrast mediun. Sixteen cases showed neoplastic bone and tumor calcification on CT.On MRI, there were 10 cases with bone destruction and periosteal reaction with iso- and hypo-intense on T1WI and iso- signals on T2WI. Twenty-six cases showed soft tissue edema and bone marrow on MRI. The soft mass were iso-signals on T1 WI and iso-hyperintense signals on T2 WI or STIR. The soft tissue edema was found hyperintense signals on T2WI or STIR. The lesions had heterogeneous enhancement especially in bone marrow with edema and adjcent soft tissue. Conclusion The X-ray, CT and MRI can reflect the pathological changes of diaphysial osteosarcoma in long bone from different aspects. Lower incidence, large bone destruction and no pathological fracture were the features of diaphysial osteosarcoma. The osteogenic type is diagnosed easily, but the osteolytic lesion should be differentiated from Ewing sarcoma, malignant giant cell tumor of bone and so on.     

Imaging of Soft Tissue Neoplasms in the Adult: Malignant Tumors

This review discusses the spectrum of malignant soft tissue tumors usually found in adults. Lesions most commonly identified in the pediatric population, as well as tumorlike masses, are not covered. Rather than presenting a complete review, the focus of this discussion is on common lesions and those lesions in which the diagnosis may be suggested on the basis of imaging. Diagnoses covered include malignant fibrous histiocytoma, fibrosarcoma, dermatofibrosarcoma protuberans, liposarcoma, synovial sarcoma, malignant peripheral nerve sheath tumor, leiomyosarcoma, aggressive vascular tumors, extraskeletal chondrosarcoma and osteosarcoma, lymphoma, and metastatic carcinoma.     

Percutaneous ultrasound-guided biopsy in the definitive diagnosis of osteosarcoma

Thirty-three patients with 35 bone lesions suspicious for osteosarcoma underwent image-guided biopsy. Of those 35 biopsies, 12 were performed with use of fluoroscopy or computed tomography (CT) guidance to target the osseous abnormality. Diagnostic magnetic resonance imaging revealed a soft tissue component in 23 cases; in these cases, biopsies were performed with use of ultrasonography (US) to target the soft tissue component of the tumor. Of the 35 tumors in which biopsy was performed, 33 (94%) were definitively diagnosed as osteosarcoma by image-guided biopsy. All 23 US-guided biopsies resulted in definitive diagnosis. Two of the 12 fluoroscopy- or CT-guided biopsies (17%) were inconclusive.     

Fluid-fluid levels in bone and soft tissue tumors demonstrated by MR imaging]

Fluid-fluid levels in bone tumors have been described in aneurysmal bone cysts and other cystic tumors of bones and soft tissue tumors. We experienced three bone tumors (simple bone cyst, bone metastasis, and osteosarcoma) and three soft tissue tumors (fibrosarcoma, two cases of cavernous hemangioma) that showed fluid-fluid levels on MR, and investigated their cause. Causes included blood in the cystic spaces, hemorrhage in the tumor, the telangiectatic component of the osteosarcoma, and the cavernous component of the hemangioma. No specific diagnosis could be made based on the finding of fluid-fluid levels. We conclude that fluid-fluid levels on MR are rather nonspecific findings in bone and soft tissue tumors and that the diagnosis should be made on the basis of other radiological and clinical findings.     

X线、CT及MRI对骨肉瘤的诊断价值

目的:探讨X线平片、CT和MRI检查在骨肉瘤的临床诊断价值.方法:回顾分析18例经穿刺或手术病理证实的骨肉瘤的X线、CT和MRI表现,并加以总结.结果:本组18例,X线平片检查漏、误诊3例(其中2例表现阴性);18例中,CT检查显示骨肉瘤的瘤骨、骨质破坏优于X线平片11例;18例中,10例行MRI检查,均表现为骨髓腔内正常的骨髓高信号被肿瘤组织所取代,肿瘤周围骨髓和软组织内均可见水肿区,6例可见骨膜反应,3例中央发生坏死囊变.结论:X线检查简便、易行,其空间分辨率高,是诊断骨肉瘤的首选方法.CT对显示结构复杂、重叠部位较多的骨肉瘤病灶有明显优势.MRI扫描在判断肿瘤的范围方面有较大优势,并能为临床定制治疗方案及预后判断提供准确的依据.X线平片、CT和MRI检查三者结合应用,有利于提高对骨肉瘤的诊断准确性.     

Benefits of molecular pathology in the diagnosis of musculoskeletal disease

The second part of this review, on the benefits of molecular pathology in the diagnosis disease, focuses on the genetics of bone tumors and metabolic disease. Unlike soft tissue tumors, the number of currently exploitable molecular abnormalities for diagnosing bone neoplasms is small, although the same gene rearrangements are found in primitive neuroectodermal tumor/Ewing sarcoma in both skeletal and extraskeletal sites. Compared with soft tissue tumors, genetic abnormalities, which are valuable to diagnosticians in skeletal disease, are often germline and post-zygotic aberrations rather than somatic translocations. In addition, the review highlights the range of disease entities classified as “osteoclast-rich lesions,” some of which harbor germline mutations. It also addresses the importance of phosphate metabolism in skeletal disorders including phosphaturic mesenchymal tumor, vitamin D-resistant rickets, and tumoral calcinosis.     

Intracortical osteoblastic osteosarcoma with oncogenic rickets

Intracortical osteosarcoma is the rarest variant of osteosarcoma, occurring within, and usually confined to, the cortical bone. Oncogenic osteomalacia, or rickets, is an unusual clinicopathologic entity in which vitamin D-resistant osteomalacia, or rickets, occurs in association with some tumors of soft tissue or bone. We present a case of oncogenic rickets associated with intracortical osteosarcoma of the tibia in a 9-year-old boy, whose roentgenographic abnormalities of rickets disappeared and pertinent laboratory data except for serum alkaline phosphatase became normal after surgical resection of the tumor. Histologically, the tumor was an osteosarcoma with a prominent osteoblastic pattern. An unusual microscopic feature was the presence of matrix mineralization showing rounded calcified structures (calcified spherules). Benign osteoblastic tumors, such as osteoid osteoma and osteoblastoma, must be considered in the differential diagnosis because of the relatively low cellular atypia and mitotic activity of this tumor. The infiltrating pattern with destruction or engulfment of normal bone is a major clue to the correct diagnosis of intracortical osteosarcoma. The co-existing radiographic changes of rickets were due to the intracortical osteosarcoma.     

Ossifying fibromyxoid tumor resembling parosteal osteosarcoma

Ossifying fibromyxoid tumor (OFMT) is a rare soft tissue neoplasm which varies in the amount of bone tissue laid down. We report on a case of OFMT in a 59-year-old male which mimicked a large parosteal osteosarcoma on radiography, MRI, and CT. T1-weighted MR images showed high-intensity areas which reflected fatty marrow. The metaplastic bone was connected to the cortex of the femur, but the tumor did not involve the medullary cavity. The tumor was irradiated and the patient was administered chemotherapy. Wide excision of the tumor and hip rotation plasty was performed. The patient has been disease free for 18 months.     

骨肉瘤亚型影像诊断(附4种亚型8例报告)

目的探讨骨肉瘤亚型的临床、影像学特征,以提高对骨肉瘤亚型的认识。方法结合文献回顾性分析经临床、病理证实的4种亚型8例骨肉瘤的影像学表现。结果3例毛细血管扩张型分别位于股骨上段、股骨下段和肱骨远段,X线显示骨质呈膨胀性、溶骨性破坏,软组织肿块,其中1例类似动脉瘤样骨囊肿;3例骨旁型位于肩胛骨、股骨中段和股骨下段,X线显示骨致密性骨块为主要表现,骨髓腔内未见异常,突起骨块与骨皮质之间见有透光带;1例骨膜型位于股骨下段,CT显示骨皮质轻度破坏,骨髓腔内未见病灶,有巨大的软组织肿块,肿块密度不均;1例髓内高分化型位于肱骨中上段,X线显示骨质囊状破坏,界限清楚,髓腔扩张,骨皮质变薄。结论该4种亚型各自具有一定影像特征,有助于诊断。     

骨肉瘤的MRI诊断(附35例分析)

总结骨肉瘤NRI表现及其特点。方法：收集经手术病理或活检证实的35例骨肉瘤，分析其MRI、X线平片征象并与手术病理对照，总结NRI诊断骨肉瘤的特征。35例均进行NRI平扫，其中18例平扫后行增强扫描。结果：骨肉瘤MRI上可表现瘤骨、骨质破坏、骨膜反应、软组织肿块等征象。此外，NRI还可显示肿瘤坏死、出血，肿瘤侵犯骨骺、关节及“跳跃”病灶。增强扫描有利于骨肿瘤良恶性的鉴别。结论：NRI可以提供比X线平片更全面的影像学信息，并指导临床治疗。     

MRI of primary lymphoma of bone: cortical disorder as a criterion for differential diagnosis

To investigate the pattern and dimension of cortical bone abnormality on magnetic resonance imaging (MRI) as a feature to distinguish primary lymphoma of bone from osteosarcoma and Ewing sarcoma, 46 patients with primary malignant bone lesions with a soft tissue mass (16 osteosarcomas, 15 Ewing sarcomas, 15 lymphomas) were examined with MRI (T1-weighted pre-/postcontrast spin-echo sequences and T2-weighted spin-echo and fast spin-echo sequences; 1.5 T system). Qualitative image analysis revealed no differences for signal characteristics and enhancement. Lymphomas appeared significantly more often homogeneous (47%; Ewing sarcoma 20%; osteosarcoma 6%/o), and patients were significantly older (cutoff point 30 years). Lymphomas showed significantly less frequent cortical abnormality (60%; Ewing sarcoma 87%; osteosarcoma 100%), complete penetration (13%; Ewing sarcoma 67%; osteosarcoma 87%), focal destruction (13%; Ewing sarcoma 40%; osteosarcoma 81%), and complete destruction (0%; Ewing sarcoma 13%; osteosarcoma 19%). In conclusion, primary lymphoma of bone is characterized by minimal cortical changes despite an accompanying soft tissue mass in a patient over 30 years of age.     

Extraskeletal osteosarcoma in the thigh: a case report

Extraskeletal osteosarcoma is a rare malignant soft-tissue tumor. There are few reports describing the radiological findings of this tumor, especially concerning its MRI and scintigraphic appearance. We report a 58-year-old man with extraskeletal osteosarcoma in the thigh. Radiographs showed small foci of mineralization in the mass. The tumor showed low intensity on T1-weighted images and predominantly high intensity on T2-weighted images, and the tumor was heterogeneously well enhanced on Gd-DTPA-enhanced T1-weighted images. Bone scintigraphy showed extraskeletal uptake in the tumor, and thallium-201 scintigraphy revealed marked inhomogeneous accumulation.