Can imaging distinguish between low-grade and dedifferentiated parosteal osteosarcoma?

BACKGROUND

Most instances of the parosteal osteosarcoma (OGS) are low-grade tumors. However, some parosteal OGSs undergo dedifferentiated transformation. Dedifferentiated parosteal OGS can cause distant metastasis and poor survival, and preoperative chemotherapy may be warranted. This study provides imaging clues for dedifferentiated parosteal OGS before treatment.

METHODS

The study retrospectively enrolled 23 patients with histologically proven parosteal OGS, including 69.6% (n = 16) low-grade and 30.4% (n = 7) dedifferentiated types. Preoperative images including radiography and magnetic resonance imaging were reviewed. The following imaging parameters and clinical outcomes were evaluated: 1) average age; 2) sex; 3) tumor size; 4) presence of string sign; 5) necrosis; 6) hemorrhage; 7) solid soft tissue component; 8) perforating vessels; 9) ossification grade; 10) marginal ossification; 11) periosteal reaction; 12) sunburst reaction; 13) bone marrow edema; 14) bone marrow invasion; 15) perifocal soft tissue edema; 16) adjacent joint involvement; 17) adjacent neurovascular bundle compression; 18) regional lymph node; 19) bone metastasis; 20) preoperative lung metastasis; 21) follow-up lung metastasis; and 22) recurrence.

RESULTS

The average maximal tumor sizes were 7.1 cm and 10.9 cm in low-grade and dedifferentiated types, respectively (p = 0.033). Sunburst periosteal reaction was visualized in two cases of low-grade type (12.5%) and four cases of the dedifferentiated type (57.1%) (p = 0.025) of parosteal OGS. None of our studied cases revealed preoperative lung metastasis. In the follow-up chest computed tomography, lung metastasis was noted in two cases of conventional type (14.2%), and four cases of dedifferentiated type (57.1%) (p = 0.040) of parosteal OGS. In receiver operating characteristic (ROC) curve analysis, the average tumor size and sunburst periosteal reaction showed good specificity (AUC = 0.070 and 0.072, respectively).

CONCLUSION

Compared with low-grade types, dedifferentiated parosteal OGS exhibits a considerably larger tumor size, more sunburst periosteal reaction, and a more frequent development of lung metastasis in the disease course. Tumor size and sunburst periosteal reaction are the most crucial imaging diagnostic factors.

Peripheral ossifying fibroma and juxtacortical chondrosarcoma in cynomolgus monkeys (Macaca fascicularis)

Literature on spontaneous primary bone tumors in nonhuman primates is sparse. This case report describes 2 different neoplastic bone lesions in 2 adult cynomolgus monkeys (Macaca fascicularis), including macroscopic, radiographic, histologic, and immunohistochemical findings. In one monkey, a firm mass located at the palatogingival junction of the left rostral maxilla was confirmed to be a peripheral ossifying fibroma in light of its histologic and immunohistochemical characteristics. In another monkey, a lobulated tumor at the right distal femur that radiographically showed moderate radiopacity with splotchy areas of mineralization was confirmed to be a juxtacortical chondrosarcoma on histologic examination. The 2 neoplastic bone lesions revealed rare histologic and immunohistochemical characteristics and contribute to the known tumor spectrum of cynomolgus monkeys.

MRI findings in parosteal osteosarcoma: correlation with histopathology

PURPOSE

To assess the role of magnetic resonance imaging (MRI), particularly signal intensity changes, in predicting the dedifferentiation of parosteal osteosarcoma, and to evaluate other factors that may affect grading on MRI.

MATERIALS AND METHODS

MRI of 12 patients with parosteal osteosarcoma diagnosed on plain radiography were reviewed with regard to size, location, extent, soft tissue component, intramedullary invasion, and signal characteristics. The findings are correlated with histopathologic results.

RESULTS

By histopathological examination there were 6 Grade I, 3 Grade II, and 3 Grade III tumors. Average size was 11 cm. All cases had a soft tissue component. Intramedullary extension was evident in 3/6 of the Grade I cases, 2/3 of the Grade II cases, and all (3/3) of the Grade III cases. T1-weighted images revealed lesions of marked hypointensity. Signal intensity on T2-weighted images varied with the presence of necrosis and hemorrhage in relation to size, regardless of the grade of the tumor. Contrast-enhanced images revealed enhancement of the solid components; no enhancement was observed in the necrotic or hemorrhagic parts.

CONCLUSION

High and heterogeneous signal on T2-weighted images of Grade I, II, and III tumors is not specific for the dedifferentiated component, due to hemorrhage and necrosis in large masses. Therefore, high signal intensity on T2-weighted images is not always a reliable way to predict the grade of the tumor. Contrast enhanced T1-weighted images can be valuable to show the solid component in the heterogeneous areas on T2-weighted images, and can be useful in guiding the biopsy.

Radiological appearances of appendicular osteosarcoma: a comprehensive pictorial review

Osteosarcoma is the most common primary malignant tumour of bone in adolescents and young adults. Hence, a comprehensive knowledge of the common and unusual imaging appearance of this tumour is essential. Correct diagnosis of the various varieties of osteosarcoma is important for optimal clinical management including staging, biopsy, treatment and follow-up of patients. This review article provides a comprehensive approach to the radiological diagnosis of the different types of appendicular osteosarcoma and illustrates the role of CT and MRI in further characterisation.

Pediatric surface osteosarcoma: clinical, pathologic, and radiologic features

BACKGROUND

Osteosarcoma (OS) arising from the surface of bone is far less common than its intramedullary counterpart. Although surface OSs share some radiographic and clinical features, they can be divided into three distinct histologic subtypes.

PROCEDURE

We reviewed the clinical, radiographic, and pathologic features of 14 cases of pediatric surface OS treated at St. Jude Children's Research Hospital between 1970 and 2003.

RESULTS

Seven patients had parosteal, five had periosteal, and two had high-grade surface OS. The median age at diagnosis was 16.2 years (range, 13.6-18.5 years). Nine patients were male; 11 were Caucasian. None had metastatic disease at diagnosis. Primary tumor sites included distal femur (n = 6), mid to proximal femur (n = 4), and mid to proximal tibia (n = 4). All 14 patients were treated with surgery, and 7 (1 with parosteal, 4 with periosteal, 2 with high-grade tumors) received chemotherapy. One patient experienced pulmonary metastasis of periosteal OS 16 months and 43 months after diagnosis; long-term disease-free survival followed resection of the metastatic tumors. Twelve patients remained alive and disease-free a median of 10 years (range, 1.5-25.4 years) after diagnosis. One patient died of high-grade surface OS 1.8 years after diagnosis, and one patient with periosteal OS died of gastric cancer 18.2 years after diagnosis of OS.

CONCLUSIONS

The histologic grade predicts the clinical behavior of pediatric surface OS. Complete resection is the treatment of choice regardless of tumor subtype. Whereas chemotherapy is not indicated for parosteal OS, its role in periosteal OS remains controversial.

Dedifferentiated parosteal osteosarcoma: The experience of the Rizzoli Institute

BACKGROUND

Dedifferentiated parosteal osteosarcoma (DPOS) is a variant of osteosarcoma in which a high-grade sarcoma coexists with a conventional parosteal osteosarcoma (c-POS), either at presentation (synchronous type) or at the time of recurrence (metachronous type). Only approximately 60 patients have been reported in the literature. The objective of this study was to analyze the clinicopathologic and radiographic features of a relatively large number of patients with DPOS in an attempt to define further the histologic and biologic behavior of this rare entity.

METHODS

In a series of 120 patients with parosteal osteosarcoma who were seen at the Rizzoli Institute from 1958 to 2000, the authors identified 29 patients who were diagnosed with DPOS. The authors reviewed the clinical and radiologic features, histologic sections, treatments, and outcomes in this group of patients with DPOS.

RESULTS

Twelve patients were male, and 17 patients were female. The patients ranged in age from 15 years to 65 yrs (average, 36 years; median, 32 years). One tumor involved the scapula, one involved the ilium, and another involved the skull. All 26 of the other tumors were located in the long bones (14 in the femur, 5 in the humerus, 3 in the tibia, 3 in the fibula, and 1 in the ulna). In 18 patients, radiographic areas of lucency were seen within an otherwise sclerotic lesion. Histologically, the dedifferentiated component was high-grade osteoblastic osteosarcoma in 14 patients, fibroblastic osteosarcoma in 10 patients, giant cell-rich osteosarcoma in 3 patients, and chondroblastic osteosarcoma in 2 patients. All tumors were Stage IIB, and invasion of the medullary canal was detected in 19 patients (65%). Twenty-eight patients underwent surgery, and 18 of those patients received chemotherapy (5 patients received neoadjuvant chemotherapy, and 13 patients received adjuvant). Nine patients were dead and 20 patients were alive (average follow-up, 107 months; range, from 3 months to 36 years) at the last follow-up. Of the nine patients who died, one patient received no treatment, five patients underwent surgery (with three patients achieving adequate margins) in combination with chemotherapy, and three patients underwent surgery only (with adequate margins achieved). Of the 20 patients who remained alive, 13 patients underwent surgery (with 10 patients achieving adequate margins) in combination with chemotherapy, whereas 7 patients underwent surgery only (all with adequate margins). Seven of the nine patients who died had widespread metastases. One patient died of causes unrelated to the tumor, and another patient died shortly after undergoing resection of a lesion in the skull.

CONCLUSIONS

Dedifferentiation occurred in approximately 24% of patients with c-POS. The prognosis for patients with DPOS was better than the prognosis for patients with dedifferentiated central and dedifferentiated peripheral chondrosarcoma.

Imaging of periosteal osteosarcoma: radiologic-pathologic comparison

PURPOSE

To review the imaging appearance of periosteal osteosarcoma, with pathologic comparison.

MATERIALS AND METHODS

Data for 40 pathologically confirmed periosteal osteosarcomas were retrospectively reviewed. Patient demographic data were recorded, and radiographs (n = 40), bone scintigrams (n = 10), angiograms (n = 2), and computed tomographic (CT) (n = 11) and magnetic resonance (MR) (n = 12) images were evaluated for lesion location and size, cortical changes, marrow involvement, and intrinsic characteristics by two musculoskeletal radiologists, with agreement by consensus. Pathology reports were reviewed for presence and predominance of histologic components (fibrous, chondroid, and osteoid), tumor grade, and marrow involvement.

RESULTS

There were 25 male (62%) and 15 female (38%) patients with an age range of 10-37 years (average age, 20 years). The most frequent lesion locations were the diaphysis of the tibia (16 patients) or of the femur (15 patients). Radiographs showed a broad-based soft-tissue mass that was attached to the cortex (all patients) and showed cortical thickening (33 patients), cortical scalloping/erosion (37 patients), and/or perpendicular periosteal reaction (38 patients) extending into the soft-tissue mass. Soft-tissue masses were well defined in 91%-100% of cases and surrounded a median of 50%-55% of the cortex. Lesions commonly showed low attenuation at CT (10 patients) and high signal intensity on T2-weighted MR images (10 patients), reflecting the high water content of these largely chondroblastic lesions. Focal areas of adjacent marrow replacement were common at MR imaging (nine patients) but represented reactive changes unless they were in direct continuity with the overlying soft-tissue mass (this was rare, occurring in only one patient, and represented marrow invasion). Review of pathology reports revealed that all lesions contained chondroid tissue, which predominated in 34 patients.

CONCLUSION

The radiologic appearance of periosteal osteosarcoma is a broad-based surface soft-tissue mass causing extrinsic erosion of thickened underlying diaphyseal cortex and perpendicular periosteal reaction extending into the soft-tissue component. Reactive marrow changes are commonly seen at MR imaging, but true marrow invasion is rare.

[Parosteal osteosarcoma: a clinical study of 48 cases]

OBJECTIVE

To investigate the way of diagnosis and therapy of parosteal osteosarcoma.

METHODS

A retrospective review was conducted of 48 patients treated at our department between June 1964 and December 2001. The average age of patients in this study was 29.2 years (13 - 47 years). Thirty-two of the patients were female; sixteen were male. The single most common site is the posterior aspect of the distal femur (in 36 patients), followed by the femur shaft (in 6 patients), the proximal tibia (in 2 patients), etc. Nine patients had been operated on before referral to our department.

RESULTS

The average follow-up period from the first operation was 5.2 (0.25 - 24) years. In 36 of the 39 patients in whom a limb-salvage procedure was performed, a segment of the tumor-bearing bone was excised along with the tumor, whereas in 3 patients only the subadjacent cortex was excised with the tumor. In the limb-sparing group, the reconstruction was achieved by means of attenuated tumor bone or allograft in 23 cases, by endoprosthetic replacement in 9 cases, and by allograft replacement in 4 cases. The local resections were wide in 35 cases, and marginal in 13 cases. After marginal surgery, local recurrence occurred in 5/13 patients, whereas it occurred in 3/35 patients treated with wide resection. Pulmonary metastases developed in 6 patients, four patients died, and 2 patients are alive with disease. There were 4 cases of fractures of bone grafts. Four patients developed an infection. Long-term survival rate is 85.8%. For tumors that invaded the medullary canal there was no statistical association with local recurrence or metastasis. There is statistical significance between surgical margin and local recurrence.

CONCLUSIONS

Wide surgical excision alone is adequate treatment for patients with conventional parosteal osteosarcoma. A tumor-free margin remains the critical factor determining overall prognosis. When a marginal excision was knowingly done to preserve a major neurovascular bundle, the risk of recurrence was less than when it was done to shell-out a presumptively benign lesion. Repeated recurrence probably increases the risk of dedifferentiation and thereby worsens the prognosis. Recurrent lesions with multiple soft-tissue satellite nodules or involvement of the neurovascular structures may however require amputation to provide sufficient local control when a wide margin cannot be achieved. An individualized resection will be performed in the future probably under the help of the advanced technique of image to distinguish the reactive zone from the normal tissue precisely.

Juxtacortical osteoma of the ulna

Acase of juxtacortical osteoma of the ulna in a 47-year-old woman is presented. She had a dense bony mass on the ulna. Radiological examinations (plain radiography, computed tomography, magnetic resonance imaging) strongly suggested a rare case of juxtacortical osteoma of a long tubular bone. The differential diagnosis included parosteal osteosarcoma, melorheostosis, osteochondroma, end-stage juxtacortical myositis ossificans, and fibrous dysplasia protuberans. The tumor was excised totally for thorough pathological examination, which revealed it to be composed of lamellar bone, suggesting that the origin was periosteal.

[Parosteal osteosarcoma (POS). Clinical and therapeutic aspects]

Parosteal osteosarcoma is a malignant bone-forming tumor, which is characterized by its superficial origin and its high structural differentiation. Because of the radiological and histological variability, finding the right diagnosis is a great challenge for physicians, radiologists, and pathologists, especially at the time of primary manifestation. Usually there is a low-grade malignancy. Often a benign tumor is imitated so that finding the correct diagnosis is indispensable. Wide resection with sufficient margin is the adequate therapy. High-grade parosteal osteosarcoma needs adjuvant chemotherapy. Our own experience with secondary dedifferentiation and the possibility of primary undergrading shows that regarding diagnostics, operative therapy, and follow-up parosteal osteosarcoma should be treated like conventional osteosarcoma.

Parosteal osteosarcoma of the skull

Parosteal osteosarcoma of the skull is a distinct surface bone tumor, with a better prognosis than conventional osteosarcoma. The most common location is on the surface of the distal femur which accounts for 46-66% of the cases. The presentation in the skull is uncommon and there are few cases reported in the literature. We describe the case of a man who developed a parosteal osteosarcoma arising from the occipital bone with extension to the parietal bone. The patient was operated and had a complete tumor resection.

Two unusual osteogenic orbital tumors: presumed parosteal osteosarcomas of the orbit

OBJECTIVE

To report two cases of suspected parosteal osteosarcoma of the orbit, with dedifferentiation into a high-grade liposarcoma occurring in one patient.

DESIGN

Two retrospective case reports.

METHODS

The clinical, radiologic, and pathologic records of two patients with suspected orbital parosteal osteosarcoma were retrospectively reviewed.

MAIN OUTCOME MEASURES

Histologic evaluation and clinical follow-up were measured.

RESULTS

The first patient was a 47-year-old male presenting with a 5-month history of painless right lower lid swelling; excision biopsy suggested a well-differentiated parosteal osteosarcoma of the orbital floor, which recurred 3 years later. Six months after excision of the recurrence, the mass demonstrated accelerated growth, and a lid-sparing exenteration was performed; histologic examination showed a high-grade liposarcoma. The patient remains disease-free at 4 years. The second patient, a 40-year-old male, presented with an 8-year history of proptosis and a right superotemporal orbital mass. The mass was excised completely at lateral orbitotomy; histologic examination suggested a well-differentiated parosteal osteosarcoma. The patient remains well 9 months postoperatively.

CONCLUSIONS

Parosteal osteosarcoma is an uncommon tumor, usually affecting long bones, that is extremely rare in the orbit. It is a low-grade sarcoma that tends to recur locally after excision but has a favorable prognosis. Dedifferentiation into a high-grade sarcoma occasionally occurs in parosteal osteosarcoma, but transformation into liposarcoma does not seem to have been previously reported. It is important to recognize dedifferentiated parosteal osteosarcoma, because the prognosis is poor, and radical treatment may be required.

Juxtacortical osteosarcoma. A distinct malignant bone neoplasm

The purpose of this report is the study of a malignant bone tumor of similar histological picture with conventional (intramedullary) osteosarcoma. Contributing factors in the study of juxtacortical osteosarcoma are the clinical, X-ray and histologic pictures. A case of parosteal osteosarcoma in a 28-year-old male is reported. In conjuction with X-ray findings we review the histological characteristics of the tumor through serial sections of the peripheral, central and parosteal parts and the findings are described in detail. In addition to the histological findings, differential diagnosis and prognosis are also discussed. From the general study of the tumor it has been shown that juxtacortical osteogenic sarcoma behaves differently in contrast to classic osteosarcoma, depending on the degree of differentiation of the tumor.

Parosteal osteosarcoma of the ring finger metacarpal in a semi-professional pianist

We report treatment of a low grade parosteal osteosarcoma of the ring finger metacarpal in a patient who would not contemplate ray amputation because of her career. Surgery involved excision of the bone, extracorporeal radiation then re-implantation.

Radiological features of osteogenic sarcoma of the jaws. A comparative study of different radiographic modalities

OBJECTIVE

To evaluate the clinical and radiological features of osteogenic sarcoma of the jaws with particular reference to the effectiveness of the radiographic modalities used.

MATERIAL AND METHODS

A total of 66 cases (57 from the English-language literature and nine new cases) were critically evaluated for the features depicted with intra-oral and panoramic radiography and CT.

RESULTS

The mean age of the patients was 36 years (median 31.5 years). There were no differences in gender distribution. A ratio of 1:1.6 between the maxilla and the mandible was found. Lesions had diffuse borders in 78% of cases and defined but not corticated borders in 22%. Twenty-nine per cent were radiolucent, 29% radiopaque and 41% mixed density. Widening of the periodontal ligament space (PDL) was seen in 14 of the 47 (28%) lesions associated with teeth and structural changes in the mandibular canal in 34% of the mandibular lesions. There was a periosteal reaction in 48% and soft tissue involvement in 33% of the lesions.

CONCLUSIONS

Widening of the PDL space was best demonstrated on periapical radiographs. Structural changes in the mandibular canal were shown mainly with panoramic radiographs. Periosteal reaction was best demonstrated by occlusal radiographs and soft tissue involvement by CT. Thorough radiological examination using periapical, occlusal and panoramic radiography, and recognition of the radiological features of osteogenic sarcoma should lead to earlier diagnosis.

Osteochondromalike parosteal osteosarcoma: a report of six cases of a new entity

OBJECTIVE

Our purpose was to describe a rare juxtacortical bone sarcoma with deceptively benign, osteochondromalike histologic characteristics. We present criteria by which this low-grade malignant neoplasm can be distinguished from other benign and malignant surface lesions of bone with particular emphasis on the imaging features.

MATERIALS AND METHODS

Six cases of a low-grade, chondroossifying parosteal sarcoma of bone were reviewed. Patients included four males and two females 11 months to 66 years old. Histologic findings from initial tumors and from recurrent tumors were reviewed. Two musculoskeletal radiologists analyzed the imaging studies, which included plain films, CT scans, MR images, and a bone scan.

RESULTS

Histologically, the lesions were characterized by a thin layer of proliferating, periosteally derived spindle cells overlying a thin, low-grade malignant cartilage cap that underwent calcification, neovascularization, and conversion into benign bone and marrow fat. These lesions were unique in that the malignant elements were only at their periphery. All six cases were initially misdiagnosed as benign lesions on pathologic evaluation. In each patient, imaging revealed a "pasted-on" ossified surface lesion with an intact underlying cortex and no medullary involvement. In three cases, recurrent tumors had histologic appearances consistent with conventional parosteal osteosarcoma. Dedifferentiation, metastases, and death occurred in one of these three cases.

CONCLUSION

To our knowledge, this surface lesion of bone has not been specifically described. Whether this tumor constitutes a distinct entity or is a specialized variant of parosteal osteosarcoma is unclear. Precise radiologic-pathologic correlation is essential for appropriate diagnosis and management.

Intracortical osteosarcoma

Intracortical osteosarcomas originate in the bone cortex and represent the rarest type of osteosarcoma. We describe the clinical, radiological and histological features of an intracortical osteosarcoma occurring in the femur of a young man and discuss the pertinent features of this tumour compared to those previously reported.

The many faces of osteosarcoma

Osteosarcoma is the most common primary malignant tumor of bone in adolescents and young adults. It accounts for approximately 15% of all primary bone tumors confirmed at biopsy. There are numerous types of primary osteosarcoma, including intramedullary (high grade, telangiectatic, low grade, small cell, osteosarcomatosis, and gnathic), surface (intracortical, parosteal, periosteal, and high-grade surface), and extraskeletal. Osteosarcoma may also occur as a secondary lesion in association with underlying benign conditions. The identification of osteoid matrix formation and aggressive characteristics usually allows prospective radiologic diagnosis of osteosarcoma. As with all bone tumors, differential diagnosis is best assessed with radiographs, whereas staging is performed with computed tomography or magnetic resonance imaging. Understanding and recognition of the variable appearances of the different varieties of osteosarcoma allow improved patient assessment and are vital for optimal clinical management including diagnosis, biopsy, staging, treatment, and follow-up.

Parosteal osteosarcoma of the maxilla

We describe the case of a 47-year-old female who presented with a small nodule in the buccal sulcus in the left maxillary incisor region. Clinical and radiographic examination revealed a small sclerotic neoplasm with a short pedicle. Histopathological examination confirmed a diagnosis of parosteal osteosarcoma. The contribution of CT to the diagnosis and management is discussed.

Dedifferentiated parosteal osteosarcoma of the radius

A 35-year-old woman presented with a painful swelling in the left distal radius that had been present for 1 year. Radiography and computerized tomography revealed a sclerotic surface lesion that had grown over the year and eroded the cortex. Histological examination demonstrated two distinct components: a cartilaginous low- to moderate-grade osteosarcoma on the surface and a high-grade osteosarcoma in the intramedullary component. This case is uncommon in two aspects: the radius is a rare site for such a tumor and the dedifferentiation was revealed at the time of the first surgery and was not secondary to recurrence.

Parosteal osteosarcoma of the tarsus

Parosteal osteosarcoma is a very rare bone tumor with a predilection for the posterior aspect of the distal femoral metaphysis. A case of parosteal osteosarcoma of the tarsus of a 23-year-old woman is reported. This is the second case of parosteal osteosarcoma of the tarsus reported in the English literature.

Parosteal osteosarcoma: value of MR imaging and CT in the prediction of histologic grade

PURPOSE

To evaluate the use of magnetic resonance (MR) imaging and computed tomography (CT) for predicting the histologic grade of parosteal osteosarcomas.

MATERIALS AND METHODS

Sixty parosteal osteosarcomas were analyzed for tumor size and location, presence of a cleavage plane, intramedullary extension, soft-tissue mass (distinct from ossified mass), and the presence and pattern of ossification. Axial and longitudinal views were evaluated for specific osseous sites within the bone. Tumors were classified as low grade (grade 1) or high grade (grades 2-3).

RESULTS

There were 32 low-grade lesions and 28 high-grade lesions. Average maximal lengths of low- and high-grade tumors were 7.7 and 15.0 cm, respectively. A cleavage plane was present in 20 (62%) low-grade and 19 (68%) high-grade lesions. On cross-sectional images, intramedullary extension was present in 13 (41%) low-grade and 14 (50%) high-grade lesions. A focal soft-tissue mass distinct from the ossific matrix was identified in 25 (89%) high-grade lesions and in only two (6%) low-grade lesions. All 17 high-grade lesions evaluated with MR imaging were of predominantly high signal intensity on T2-weighted images.

CONCLUSION

A poorly defined soft-tissue component distinct from the ossific matrix is the most distinctive feature of high-grade parosteal osteosarcoma and may be an optimal site for biopsy.

Adjuvant local treatment of parosteal osteosarcoma

Four patients with parosteal osteosarcoma of the distal femur were treated by resection and insertion of cement. The resection was marginal in 3 patients and intralesional in one. The histology was grade 1 in 3 and grade 2 in one. The cement was subsequently removed and a fibular autograft used for reconstruction. The average follow up was 88 months (range 20 to 161 months). The function of the affected limb was excellent. The best time to remove the cement was after one year.

Low-grade parosteal osteosaracoma of the ulna with dedifferentiation into high-grade osteosarcoma

This report describes a low-grade parosteal osteosarcoma of the ulna with dedifferentiation into high-grade osteosarcoma. The clinical, pathological, and imaging findings are described and discussed.

Atypical lipomas, liposarcomas, and other fat-containing sarcomas. CT analysis of fat element

The radiographic appearance of fat in and around soft tissue sarcomas was evaluated to assess the diagnostic potential of this finding. Based on the distribution of fat and other components, these tumors are classified into three types.

Case report 835: Parosteal osteosarcoma involving the left radius

A case of parosteal osteosarcoma arising in the radius was presented. The site is uncommon, being represented in about 1% of all reported cases of parosteal osteosarcoma. The clinical and radiographic characteristics of this lesion were described and the histological as well as the differential diagnosis discussed.

Osteosarcoma presenting as supracrestal bone formation

We report an unusual case of maxillary osteosarcoma presenting as supracrestal bone formation in a 41-year-old woman. This case is of interest from the point of view of radiographic appearance of supracrestal bone formation with widened periodontal ligaments and the buccal and palatal swelling of the tissues. Moreover, to the best of our knowledge, the histopathologic evidence of cemental resorption has not been reported earlier.

Parosteal osteosarcoma

A case of parosteal osteosarcoma is reported. In spite of the pathognomonic plain radiographic signs of parosteal osteosarcoma, it is very uneasy to differentiate it from myositis ossificans circumscripta in the mature stage. CT and MRI defined the extent of the tumor into the soft tissue, the medullary and cortical invasion and gave more information about the composition of the lesion.