Parosteal osteosarcoma with low grade chondrosarcoma and liposarcoma components. A rare histologic variant. Case report and literature review

INTRODUCTION

conventional parosteal osteosarcoma is an uncommon malignant bone tumor, comprising 4% of all osteosarcomas. Although rare, parosteal osteosarcoma is the most common type of osteosarcoma of the bone surface. We present the clinical, histological and imaging characteristics of a rare histologic variant of a parosteal osteosarcoma, review the literature and emphasize the importance of radio-pathological correlation as well as the interpretation of a representative biopsy in order to obtain the correct diagnosis.

CASE REPORT

a 36-year old woman began her condition one year prior to admission to the hospital with increased volume in the left knee and pain. Image studies showed a juxtacortical heterogeneous tumor localized on the posterior surface of the distal femoral metaphysis. An incisional biopsy was performed, with the diagnosis of a Parosteal Osteosarcoma and a wide surgical resection was undertaken. According to the findings of the surgical specimen, the diagnosis of a Parosteal Osteosarcoma with low grade chondrosarcoma and liposarcoma components was made. The knowledge of this rare parosteal osteosarcoma variant can lead the orthopedic oncologists to avoid overlooking the adipose component and provide adequate surgical margins.

CONCLUSION

we present the clinical, histological and imaging characteristics of a Parosteal Osteosarcoma with low grade liposarcoma and chondrosarcoma components.

Dedifferentiated Primary Parosteal Osteosarcoma of the Temporal Bone in a 19-Year-Old Patient: A Case Report

Osteosarcoma is the most common primary malignant tumor affecting the bone but is a rare occurrence in the head and neck region. Complete surgical resection with wide surgical margins is currently the main treatment strategy for osteosarcoma but can be hard to achieve due to the complex anatomy of the head and neck. We report the first case of primary high-grade dedifferentiated parosteal osteosarcoma arising from the temporal bone in published literature. The 19-year-old patient presented with a left retroauricular lesion measuring 3 cm in diameter. Radiographic imaging and biopsy suggested the diagnosis of intermediate-grade chondrosarcoma, but definitive histopathology confirmed a diagnosis of dedifferentiated parosteal osteosarcoma. The tumor was resected with wide margins, removing the underlying temporal bone, periosteum and overlying soft tissue through a lateral temporal bone resection. The middle ear was reconstructed with cartilage grafting, and the dura of the posterior and middle cranial fossa was covered using temporal fascia grafts and local transpositional flaps. The patient is recurrence free 10 months after treatment. This report was assembled following CARE [The CARE guidelines (for Case Reports)] guidelines and describes clinical, histological, and radiological manifestations of our patient's rare clinical entity and may provide more data in treating patients with osteosarcoma affecting the anatomically complex head-and-neck region.

On the importance of considering disease subtypes: Earliest detection of a parosteal osteosarcoma? Differential diagnosis of an osteosarcoma in an Anglo-Saxon female

A case of potentially dedifferentiated parosteal osteosarcoma was found in the proximal humerus of an adult female buried in the late Anglo-Saxon cemetery of Cherry Hinton, Cambridgeshire, UK. Key features include a large, dense, lobulated mass attached to the medial metaphysis of the proximal humerus by a broad-based attachment, accompanied by cortical destruction and widespread spiculated periosteal reaction. Radiographic images confirm medullary involvement, lack of continuity between the cortex and external mass, a radiolucent cleavage plane and possible radiolucent zones within the bony masses. Differential diagnoses considered include osteochondroma, myositis ossificans, fracture callus, as well as the primary malignancies of osteosarcoma and chondrosarcoma, and their various subtypes. The macroscopic and radiographic analysis of the tumor is described and discussed within clinical and paleopathological contexts. One of only 19 uncontested examples of osteosarcoma from past human populations, most of which remain unconfirmed, this case represents what we believe to be the earliest, and probably singular, bioarcheological example of parosteal osteosarcoma in human history.

[Dedifferentiated diaphyseal juxtacortical osteosarcoma of ulna with metastasis to the lung]

Dedifferentiated parosteal osteosarcoma is a variant in which a high grade osteosarcoma coexists with a parosteal osteosarcoma. We report the case of a 20-year-old female patient who presented with six months of evolution of pain and functional limitation of the right forearm, with no apparent cause; radiographs were performed, observing a tumoral lesion in the diaphysis of the right ulna. Physical examination showed pain upon palpation in the diaphysis of the ulna and limitation of prone-supination. Axial computed tomography of the thorax revealed metastatic disease in the upper lobe of the left lung. An incisional biopsy was performed on the right ulna, with a report of dedifferentiated parosteal osteosarcoma. Therefore, the patient was managed with neoadjuvant chemotherapy with cisplatin and doxorubicin until completing three cycles. Surgical treatment consisted of intercalary resection of the diaphysis of the right ulna, plus reconstruction of the microvascularized autologous graft of the right fibular diaphysis and graft stabilization with 3.5 mm dynamic compression plate (DCP) and one-third tubular plate. In the same procedure, pulmonary metastasectomy was performed by thoracoscopy. Post-surgical histopathological report with 100% necrosis. Currently, the patient is asymptomatic, with no evidence of tumor activity. Dedifferentiated parosteal osteosarcoma is a rare pathology, but should be suspected as a differential diagnosis in the presence of a parosteal osteosarcoma; it should be taken into account that this disease can metastasize due to its dedifferentiated pattern. It is important to plan a surgical treatment that allows an adequate functional reconstruction, always taking into account the oncological principle.

Periosteal osteosarcoma of the mandible: a case report

This report describes a rare case of a periosteal osteosarcoma of the mandible in a 50-year-old African-American woman who showed no underlying bony changes at panoramic radiography or computed tomography. This report describes the diagnostic workup used to obtain the definitive diagnosis and the surgical treatment and recommended method for subsequent tumor surveillance. Emphasis is placed on distinguishing periosteal osteosarcomas as a separate entity from conventional intraosseous osteosarcomas in the head and neck region.

Imaging features of juxtacortical chondroma in children

BACKGROUND

Juxtacortical chondroma is a rare benign bone lesion in children. Children usually present with a mildly painful mass, which prompts diagnostic imaging studies. The rarity of this condition often presents a diagnostic challenge. Correct diagnosis is crucial in guiding surgical management.

OBJECTIVE

To describe the characteristic imaging findings of juxtacortical chondroma in children.

MATERIALS AND METHODS

We identified all children who were diagnosed with juxtacortical chondroma between 1998 and 2012. A single experienced pediatric radiologist reviewed all diagnostic imaging studies, including plain radiographs, CT, MR and bone scans.

RESULTS

Seven children (5 boys and 2 girls) with juxtacortical chondroma were identified, ranging in age from 6 years to 16 years (mean 12.3 years). Mild pain and a palpable mass were present in all seven children. Plain radiographs were available in 6/7, MR in 7/7, CT in 4/7 and skeletal scintigraphy in 5/7 children. Three lesions were located in the proximal humerus, with one each in the distal radius, distal femur, proximal tibia and scapula. Radiographic and CT features deemed highly suggestive of juxtacortical chondroma included cortical scalloping, underlying cortical sclerosis and overhanging margins. MRI features consistent with juxtacortical chondroma included isointensity to skeletal muscle on T1, marked hyperintensity on T2 and peripheral rim enhancement after contrast agent administration. One of seven lesions demonstrated intramedullary extension, and 2/7 showed adjacent soft-tissue edema.

CONCLUSION

Juxtacortical chondroma is an uncommon benign lesion in children with characteristic features on plain radiographs, CT and MR. Recognition of these features is invaluable in guiding appropriate surgical management.

Parosteal osteosarcoma

In this retrospective clinical study, 6 cases of osteosarcoma of the bone have been analyzed. Five patients were with parosteal osteosarcoma and one with periosteal osteosarcoma. The study was performed at the Clinic for Orthopaedic Surgery in Skopje, Macedonia, from 1995 to 2005. This tumor represents 1.5% of all primary bone tumors treated at the Clinic in the 11 year period. The age of the 6 patients (2 female and 4 male) ranged from 8 to 39 years (average 23.8). The history analysis of the patients showed misinterpreted diagnosis in 50% of the cases, with 83.3% rate of local recurrence, 33.3% of metastases and 33.3% of mortality. Follow-up varied from 11 months to 9 years (average 4.5). The clinical and histopathological findings (identical with those reviewed in the literature) confirmed occurrence of two biologically different types of parosteal osteosarcoma: predominant type is originally "benign" but has a definite malignant potential, causing metastases after long symptom-free interval. The other type is highly malignant from the beginning. More radical surgery is recommended for the latter category of tumors, followed by chemotherapy. Compartmental, radical "en bloc" resection, followed by regular review of the patients, is recommended for the former (Tab. 1, Fig. 3, Ref. 20). Full Text (Free, PDF) www.bmj.sk.

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.

A comparison of intramedullary and juxtacortical low-grade osteogenic sarcoma

While low-grade juxtacortical and low-grade intramedullary osteogenic sarcomas are histologically indistinguishable, they have been studied as separate entities. We retrospectively reviewed the clinical, radiographic, histologic features and treatment of 59 patients treated surgically to compare the rate of local recurrence, grade progression, and survival between low-grade intramedullary and low-grade juxtacortical osteogenic sarcoma. Forty-five (76%) patients were treated for low-grade juxtacortical osteogenic sarcoma and 14 (24%) were treated for low-grade intramedullary osteogenic sarcoma. Local recurrence rates of 7% were similar for both groups studied. The rate of distant metastases was also similar for both groups. . The rate of dedifferentiation for the entire group was 29%. Dedifferentiated lesions were treated with adjuvant chemotherapy in 16 of 17 cases. Recurrence preceded dedifferentiation in four cases. Five-year survival was over 90% in both groups. Low-grade intramedullary and low-grade juxtacortical osteogenic sarcoma were clinically indistinguishable with identical rates of local recurrence, distant metastases, dedifferentiation, and survival.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Proceedings of the SRBR-KBVR osteoarticular section meeting of June 29, 2004 in Antwerp. The variable imaging appearance of osteosarcoma

The purpose of this brief review is to give an overview of the different imaging features of the various types of osteosarcoma, based on their macroscopic location within the musculoskeletal system. Further subdivision can be made by histological criteria and/or more specific location. Standard radiographic features allowing their differentiation will be highlighted. The value of cross-sectional imaging in the pre-operative staging, assessment of local extension, monitoring of response to treatment and guiding biopsy will be emphasized as well.

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.

[Pathomorphology of parosteal osteosarcoma. Experience with 125 cases in the Hamburg Register of Bone Tumors]

Parosteal osteosarcoma is a rare low-grade bone tumor. It occurs between the 2nd and 8th decade of life. In our own series of 125 parosteal osteosarcomas, most patients were aged between 30 and 40. The most frequent location was the distal dorsal femur. Until clearly proven otherwise, a bone-forming tumor in this location has to be regarded as a parosteal osteosarcoma. Of all parosteal osteosarcomas 77% are located in the lower extremity, with a female sex predominance in this location (62%); 18% are located in the upper extremity; 15% of all parosteal osteosarcomas are located in the humerus. Just 6% of all parosteal osteosarcomas are observed in the skull, the spine, and the pelvis. The tumor is characterized by hyalinized fibrous stroma with a low cell content without substantial nucleus polymorphism and variably dense bony trabeculae. The diagnosis can be difficult due to highly differentiated areas with fat tissue within the marrow and very uniformly bony structure. The operation material has to be analyzed very carefully, because the extent of dedifferentiated areas and most probably also the extent of invasion of the medullary cavity determine the prognosis and occurrence of recurrencies. The tumor is most commonly misinterpreted as osteochondroma or heterotopic ossification. Paying attention to all radiologic and histologic criteria,osteoblastic eccentrically located high-grade osteosarcomas can be clearly distinguished from parosteal osteosarcoma. An intramedullary located low-grade osteosarcoma,which is differentiated like a parosteal osteosarcoma,is histologically indistinguishable from the parosteal variant. This variant requires the synthesis of all available data to find the correct diagnosis. The parosteal osteosarcoma shows like no other tumor the necessity of close cooperation of all involved disciplines for diagnosis and therapy.

[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.

[Juxtacortical osteosarcoma of tibia from a medieval cemetery of Budapest]

Juxtacortical osteosarcoma occurred on the right tibia and fibula of a 20-22 years old man found in a medieval period cemetery of Budapest. MACROSCOPIC DESCRIPTION: The tumor is located circumferentially on the midshaft of the tibia and fibula and appears cone-shaped. The lesion measured 160 mm in length and 3-5 mm in height. The surface of the tumor is irregular, rough, in some areas shows spicules. These spicules averaged 2-4 mm in length and 1-2 mm in diameter. The anterior and medial surface of the tibia is completely covered by osseous tumor. RADIOGRAPHY: The X-ray study demonstrates the medullary involvement, with mixed osteolytic and osteoblastic areas. Tumor infiltration of the cortex is also apparent as irregular rarefication and lytic lesions. In some areas a "sunburst" picture could be seen. The X-ray picture is characteristic for juxtacortical osteosarcoma. MICROSCOPIC EXAMINATION: stereomicroscopy of specimens shows a sponge-like structure of the surface. The cortical bone is completely destroyed and deep cavities are seen between spiculous and gyrificated neoplastic bone. The spiculae are varied in length and thickness. Irregular bulky bone trabeculae demonstrating uncontrolled neoplastic reaction could be detected. By light microscopic examination severe destruction, osteolytic lesions are seen both in the cortical bone and in the cancellous bone in the peripheral parts of the tumors. Within the neoplastic bone only few remnants of the primary (normal) bone structure could be demonstrated. No reparative reactions were seen next to the osteolysis, the collagen fibers and lamellas are destroyed. Beside the destruction of original bone larger structures composed of irregular newly built nepotistic bone trabeculae can be detected. The newly formed trabeculae (spiculae) contain a tumorous ground substance (probably osteoid tissue) with few collagen fibers, and these areas are covered with a thin bony lamella. In some areas the neoplastic structures are in intimate contact with the original cancellous bone remnants. IMMUNOHISTOCHEMISTRY: Both the osteosarcoma and chondrosarcoma show osteoid and bone neoformation while in the chondrosarcoma type II collagen could also detected. By immunohistochemical reactions no type II and III collagen, only type I collagen reaction was positive. This means that no cartilaginous tissues were present in the tumor. Scanning electron microscopy of these specimens shows sponge-like structures. The tumor reveals irregular trabecular and spicular texture,the spicules are various in diameter and in some spiculae rounded deposits attached to the surface. In our case we found typical radiological and histological picture of the juxtacortical 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.

The role of imaging modalities in the diagnosis of primary dedifferentiated parosteal osteosarcoma

Dedifferentiated parosteal osteosarcoma (dd-POS) is defined as high-grade sarcomatous components coexisting with low-grade POS components. With regard to the histological diagnosis of dd-POS, the sampling of a small area of dedifferentiation through the densely mineralized POS can be a problem. In this situation, imaging is important to identify the area with the highest possibility of dedifferentiation. We report a patient in whom dedifferentiation was shown by computed tomography (CT) and magnetic resonance imaging (MRI). CT revealed a radiolucency in a highly mineralized area. T2-Weighted MRI showed a relatively high signal intensity, corresponding to the radiolucency, surrounded by a very low signal intensity area. Furthermore, gadolinium-enhanced T1-weighted MRI showed marked enhancement. Based on these imaging techniques, the condition was diagnosed as most likely to be a dd-POS, although a representative sample was not accessible by incisional biopsy. Neoadjuvant chemotherapy was administered, followed by wide resection and adjuvant chemotherapy. Four years after the surgery, partial lobulectomy was required because of a pulmonary metastasis. Three years after the second surgery, the patient remained well without evidence of metastases. Based on the initial diagnosis and, consequently, the optimal treatment of combined chemotherapy and wide resection, our patient showed a good clinical outcome.

Imaging recurrent parosteal osteosarcoma

The aim of this study was to document the imaging features of recurrent parosteal osteosarcoma. The clinical and imaging records of 33 patients with a parosteal osteosarcoma referred to an orthopaedic oncology service over a 17-year period were retrospectively reviewed. The mode of identification of locally recurrent tumour was noted, together with the management and clinical outcome. Five patients developed a local recurrence of their parosteal osteosarcoma ranging from 6 months to 10 years after initial surgery. In 4 patients the recurrence was first suspected clinically due to the development of a mass. In the fifth patient recurrence was first detected on routine follow-up radiography. In 4 patients the recurrence could be identified on radiography as a mineralized mass. All the recurrences were readily identified on MR imaging, despite artefacts from prostheses. The recurrences were also evident in the 3 cases in which bone scintigraphy was performed. Local recurrence of parosteal osteosarcoma is adequately detected with a combination of clinical examination and conventional radiography. MR imaging is required to stage local recurrence or where radiography has failed to confirm clinically suspected recurrence. The routine use of MR imaging to follow-up patients is of doubtful value because of the frequently long time between initial surgery and relapse.

Telangiectatic dedifferentiation of a parosteal osteosarcoma

A unique case of parosteal osteosarcoma (POS) of the proximal femur, with areas of telangiectatic dedifferentiation, in a 28-year-old woman is reported. The patient had a 7-week history of pain and swelling in her right thigh. A biopsy diagnosis of POS was established. The patient was treated with two cycles of intraarterial chemotherapy, followed by limb salvage surgery. Histological examination of the resected specimen showed POS with areas of dedifferentiation composed of highgrade telangiectatic osteosarcoma with associated secondary aneurysmal bone cyst change.

Juxtacortical osteogenic sarcoma of mandible. A case report

Juxtacortical osteogenic sarcoma of bone is a relatively uncommon form of osteogenic sarcoma. In the jaw bones, it is extremely rare. Here, we present a case of Juxtacortical Osteogenic Sarcoma of mandible in a 45 year old man which presented as an epulis in the mandibular incisor region.

Dedifferentiated parosteal osteosarcoma with high-grade osteoclast-rich osteogenic sarcoma at presentation

We report a case of a 32-year-old woman who presented with parosteal osteosarcoma of the distal femur with simultaneous dedifferentiation to a high-grade osteoclast-rich osteogenic sarcoma. This pattern of dedifferentiation is rare, particularly at the time of presentation. We are aware of three other somewhat comparable cases in the literature; however, none is quite similar to our case.

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.

Long bone surface osteomas: imaging features that may help avoid unnecessary biopsies

OBJECTIVE

Our purpose is to show that a combination of imaging techniques and periodic radiologic follow-up offers an alternative to biopsy in certain patients with long bone surface osteomas.

CONCLUSION

Asymptomatic lesions that are consistent with osteoma on a combination of imaging studies can be followed up clinically and radiographically, allowing patients to avoid unnecessary biopsies.

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.

Recurrent parosteal osteosarcoma of the talus in a 2-year-old child

Parosteal osteosarcoma is an uncommon, low-grade malignant bone tumor and is found in an older age group than conventional osteosarcoma. We present a talar parosteal osteosarcoma that recurred twice in a 2-year-old child. To our knowledge, this is the youngest patient reported with a parosteal osteosarcoma. The talus is an unusual site for parosteal osteosarcoma. Inadequate resection due to a diagnosis of juxtacortical chondroma resulted in recurrence of the tumor. The age of the patient, the thick cartilaginous cap, and well-differentiated trabecular bone all contributed to the critical erroneous diagnosis.

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 cervical vertebra in a dog

A 12-year-old Maltese terrier was evaluated for progressive tetraparesis and neck pain. On radiographs, there was a periosteal reaction involving the fourth cervical vertebra. Myelographically, there was extradural compression of the spinal cord associated with the lesion. The dog was euthanized and necropsied. Histopathologic diagnosis was parosteal osteosarcoma of the vertebra.

Conventional and dedifferentiated parosteal osteosarcoma. Diagnosis, treatment, and outcome

BACKGROUND

Dedifferentiated parosteal osteosarcoma (dd-POS) designates high grade transformation, of conventional low grade parosteal osteosarcoma (c-POS). The paradigm of preoperative diagnosis, neoadjuvant chemotherapy, and wide local excision has not been adequately evaluated for dd-POS, as it has been for conventional high grade intramedullary osteosarcoma.

METHODS

A retrospective review was conducted of 28 patients treated at the authors' institution between January 1980 and December 1992 for an osteosarcoma arising on the surface of the bone diagnosed as either c-POS or dd-POS. The clinicopathologic features, diagnosis, treatment, and patient outcome were analyzed.

RESULTS

A dedifferentiated component was identified in 12 of 28 tumors (43%). Neither the presence of radiolucencies (77% in c-POS and 100% in dd-POS, P = 0.06) nor medullary invasion (42% in c-POS and 50% in dd-POS, P = 0.28) distinguished dd-POS from c-POS. However, all patients who presented with focal hypervascularity on an arteriogram defined the high grade component of dd-POS that was confirmed by selective needle biopsy. This differed significantly (P = 0.00003) from c-POS. None of the patients with c-POS died of the disease (median survival duration, 77 months; range, 16-152 months). Six patients (35%) developed a local recurrence, but five were treated successfully with further surgery. In the dd-POS group, 7 of the 12 patients died of the disease. Ten patients with dd-POS received preoperative chemotherapy (IA cis-diamminedichloroplatinum, IV doxorubicin), and a good response (> 90% necrosis of high grade component) was observed in four. Among patients whose disease was localized, continuous disease free survival was prolonged significantly (P = 0.03) in patients with a good response (median, 75 months) compared with those who responded poorly (median, 13 months). Five patients remained continuously disease free (median, 66 months, range, 29-95 months).

CONCLUSIONS

Wide surgical excision alone is adequate treatment for patients with c-POS. Recognition of dedifferentiated areas with angiography and percutaneous biopsy of hypervascular areas should prompt the administration of chemotherapy and wide local excision to optimize patient outcome.

Parosteal osteoma of bones other than of the skull and face

BACKGROUND

Osteoma of the skull and facial bones is not uncommon, is usually asymptomatic, and may be associated with Gardner's syndrome. Osteomas involving other bones are unusual.

METHODS

The authors describe 14 cases (eight men and six women from age 21-66 years) of parosteal osteoma of bones other than of the skull and face.

RESULTS

Thirteen lesions involved long bones, and one involved the clavicle. A long-standing (18 months to 31 years) mass was reported in seven patients. Symptoms of pain, a mass, or both were present in all except three patients who were asymptomatic. Lesions ranged from 2.5 to 20 cm in greatest dimension. Histologically, they blended with the cortex, did not infiltrate the medullary cavity, and consisted of dense sclerotic lamellar bone with haversian systems, similar to the architecture of normal cortical bone. There was no spindle cell proliferation. Nine patients underwent resection, four had biopsy, and one had debulking. With a follow-up of 1-23 years, no recurrence or metastasis was reported.

CONCLUSIONS

Parosteal osteoma must be distinguished from parosteal osteosarcoma, a low grade malignant neoplasm. If radiographs do not identify areas of radiolucency and sections do not contain spindle cells, the diagnosis of parosteal osteoma is justified.

Parosteal osteosarcoma of the talus

A case of parosteal osteosarcoma in the very rare location of the talus is presented. The radiological, pathological, and clinical characteristics of parosteal osteosarcoma are described and the differential diagnosis discussed.

[A case of parosteal osteosarcoma at the cranial vault]

A rare case of parosteal osteosarcoma of the cranial vault has been reported. A 32-year-old male was admitted complaining of a hard scalp mass at the left temporoparietal region for several years. On admission he showed no neurological abnormalities. The craniogram, CT and MRI revealed a calcifying mass attached by a small stalk to the skull, and a radiolucent cleft between the tumor and the skull. On operation, the tumor proved to be hard, and it existed between the temporal muscle and the periosteum. A small tumoral attachment existed at the parietal region. The tumor was detached from the skull and the surrounding cranial bone was removed. The histological diagnosis was parosteal osteosarcoma. There have been only 12 cases of parosteal osteosarcoma of the skull reported. The pathological, neuroradiological findings and treatment of parosteal osteosarcoma were the main topics of discussion. This disease should be considered as one of the possible etiologies when a patient with a tumor of the skull is encountered.