Parosteal osteosarcoma. A clinicopathological study

Osteochondroma-like parosteal osteosarcoma: A case highlighting diagnostic challenge and surgical advances

Parosteal osteosarcomas are uncommon malignant bone tumors that arise from the bone surface. Their heterogenous components can present challenges in diagnosis. We present a case of a rare variant of this tumor known as an osteochondroma-like parosteal osteosarcoma, which was initially misdiagnosed as a cartilaginous tumor on core needle biopsy. Surgical resection of the tumor ultimately allowed for definitive diagnosis. Our case demonstrates the limitations of needle biopsy in diagnosing variants of parosteal osteosarcoma and the vital role of multidisciplinary discussions in guiding diagnosis and treatment. Furthermore, our case utilizes 3-dimensional printing technology in the surgical treatment, and illustrates the recent advances in patient-specific surgical techniques.

Effect of adjuvant chemotherapy on localized dedifferentiated low-grade osteosarcoma: a systematic review

PURPOSE

Dedifferentiated low-grade osteosarcomas, which are considered high grade malignancies, can arise from the dedifferentiation of parosteal and low-grade osteosarcomas. Usually, localized dedifferentiated low-grade osteosarcomas are treated by wide resection, and the efficacy of adjuvant chemotherapy is controversial. We conducted a systematic review of studies that investigated the rates of mortality and significant events, such as recurrence and metastases, in localized dedifferentiated low-grade osteosarcoma patients who received wide resection only and in those who received wide resection and (neo-)adjuvant chemotherapy.

METHODS

We identified 712 studies through systematic searches of Embase, PubMed, and the Cochrane Central Register of Controlled Trials databases. Of those studies, seven were included in this review and none were randomized controlled trials. In the seven studies, 114 localized dedifferentiated low-grade osteosarcoma patients were examined.

RESULTS

Mortality rates of the resection plus chemotherapy (R + C) and the resection only (Ronly) groups were 20.3% and 11.4%, respectively [overall pooled odds ratio, 1.59 (P = 0.662); heterogeneity I2, 0%]. The local recurrence or distant metastasis rate in the R + C group was 36.7% and that in the Ronly group was 28.6% [overall pooled odds ratio, 1.37 (P = 0.484); heterogeneity I2 was 0%].

CONCLUSIONS

Results show a limited efficacy of adjuvant chemotherapy for localized dedifferentiated low-grade osteosarcoma. However, because this was a systematic review of retrospective studies that examined a small number of patients, future randomized controlled trials are needed.

Is still effective massive allograft reconstruction in parosteal osteosarcoma of the distal femur? Review of the literature and advantages of newer technologies

PURPOSE

Parosteal Osteosarcoma is a well-differentiated, low-grade bone sarcoma. It most commonly occurs in the third decade of life, usually in the distal femur. This study aims to perform a literature review about the types of reconstructions reported and to analyze the results of an updated technique of resection using custom-made 3D-printed cutting guides.

METHODS

We perform a systematic literature review about parosteal osteosarcoma, evaluating treatments, margins, local recurrence, complications, and functional results when available. We also report a case treated in our Center with a revisited technique introducing custom-made 3D-printed cutting guides.

RESULTS

We analyzed 12 studies with a total of 151 patients. The distal femur was the most frequently reported site (81.5%). After distal femur resection, reconstruction was performed with graft in most cases (48%), followed by prosthetic reconstruction (40%). Margins were wide in 85.5% of cases. The total incidence of local recurrence was 11%. Functional results were excellent in all cases, with a mean MSTS score of 86%. In our case, with the help of the jigs, the surgical technique was relatively easy, graft fusion excellent and fast, margins wide, and functional results excellent.

CONCLUSIONS

In the literature, the most commonly used type of reconstruction after resection is biological with graft. Indeed, despite the increasing number of prosthetic reconstructions, the historical diaphysometaphyseal hemiresection and graft is still indicated in parosteal osteosarcoma of the distal femur. New technologies, such as the jigs we used, allow significant advantages during the procedure: reduce the resection and graft preparation time, allow a better match between components, and help to obtain safer margins, sparing as much bone as possible.

Dedifferentiation in bone and soft tissue sarcomas: How do we define it? What is prognostically relevant?

Dedifferentiation traditionally is defined by descriptive criteria as a tumor showing an abrupt change in histology from a conventional, classic, low-grade appearing neoplasm to a tumor that is more cellular, pleomorphic and "high grade", with grading typically being performed by subjective criteria. The dedifferentiated areas range from areas with recognizable histologic differentiation which differs from the primary tumor (such as an osteosarcoma arising from a low-grade chondrosarcoma) to areas containing sarcomas without specific histologic differentiation (such as pleomorphic or spindle cell sarcoma). Many, but not all, dedifferentiated tumors are aggressive and associated with significantly shorter survival than their conventional counterparts, even grade 3 conventional tumors. As a result, dedifferentiated tumors are generally considered to be clinically aggressive and as a result, more aggressive surgery or the addition of (neo)adjuvant chemotherapy is often considered. However, long-term (greater than 20 year) survivors are reported in the most common dedifferentiated bone and soft tissue sarcomas. Moreover, use of mitotic criterion for defining dedifferentiation in dedifferentiated liposarcoma as well as grading (by the French system) have been found to be associated with survival. This paper reviews the literature on dedifferentiated chondrosarcoma, dedifferentiated liposarcoma, dedifferentiated chordoma and dedifferentiated parosteal osteosarcoma. As a result of that review, recommendations are advocated to identify evidence-based, objective diagnostic and grading criteria for dedifferentiation that are appropriate for each tumor type. Adding such criteria will improve consistency in diagnosis worldwide, allow easier comparison of clinical research performed on dedifferentiated tumors and help communicate (to patients and clinicians) the tumors with highest risk of clinically aggressive behavior, to allow appropriate and personalized treatment planning.

Pediatric parosteal osteosarcoma of the distal radius causing extensive erosive mass effect of the adjacent ulna: a case report

INTRODUCTION

Parosteal osteosarcomas are low-grade bony malignancies that are treated primarily with surgical resection and reconstruction. This report discusses a unique case of a pediatric patient who presented with a parosteal osteosarcoma of the distal radius causing extensive erosive mass effect and growth disturbance of the adjacent ulna. Likely due to their slow-growing nonaggressive nature, parosteal osteosarcomas have not been previously described to abut adjacent bony structures through direct contact. The patient presented in a significantly delayed manner due to social circumstances, inadvertently revealing this novel behavior. This report reviews this rare case and describes the current understanding of this tumor.

CASE PRESENTATION

The patient is a 13-year-old male who presented with a parosteal osteosarcoma of his distal radius. He presented with a palpable wrist mass and wrist stiffness. He presented in a delayed manner with advanced local disease due to social factors. Imaging revealed an osseous radial mass that abutted the ulna and likely stunted its growth. The patient ultimately underwent complex resection and allograft reconstruction of both his distal radius and ulna. Intraoperative pathology was confirmed to have negative tumor margins. Allograft reconstruction of the radius and ulna was performed utilizing patient-specific custom cutting guides. At the 6-month postoperative visit, the patient had no recurrence of the mass, minimal pain, and had almost regained range of motion of the extremities. Clinical radiographs at the 6-month postoperative visit demonstrated allograft incorporation.

CONCLUSIONS

A previously unreported case of pediatric parosteal osteosarcoma of the distal radius with erosion of the adjacent ulna through direct contact is presented. The challenges in and the importance of arriving at a definitive diagnosis in a timely manner for the proper treatment of this malignancy are emphasized.

Conservative surgical management of surface osteosarcoma using 3D printing technology: An unusual case report and literature review

INTRODUCTION AND IMPORTANCE

Surface osteosarcoma, a rare variant of osteosarcoma, poses unique challenges in diagnosis and treatment. This report discusses the application of 3D printing technology in the surgical management of a complex case involving a 27-year-old female patient with surface osteosarcoma in the proximal tibia.

CASE PRESENTATION

A 27-year-old female patient presented with a progressively growing mass on her right knee, initially misdiagnosed as a benign bone tumor. Over five years, the lesion expanded from a well-corticated metaphyseal-epiphyseal outgrowth on the proximal tibia to involve the anterior tibial tuberosity. Radiological and histological evaluations confirmed well-differentiated paraosteal surface osteosarcoma. A multidisciplinary team opted for a conservative surgical approach, including resection of the anterior tibial tuberosity and patellar tendon. Precision was enhanced through 3D printing technology, which provided custom cutting guides. The reconstruction involved non-vascularized peroneus and iliac crest bone grafts.

CLINICAL DISCUSSION

Accurate differentiation from benign lesions presents challenges. Achieving surgical resection with clear margins is pivotal for favourable outcomes, particularly in young patients. Chemotherapy yields limited benefits in low-grade surface osteosarcomas. Functional prognosis hinges on effective post-resection reconstruction. 3D printing technology facilitates meticulous surgical planning and guidance, enhancing the success of conservative surgical interventions.

CONCLUSION

This case underscores the significance of a multidisciplinary approach, accurate diagnosis, and the integration of 3D printing technology in managing surface osteosarcomas. Conservative surgical resection, guided by precise planning and reconstruction, is critical for preserving functionality. Continued research and the adoption of innovative techniques hold promise for improving the quality of life and functional outcomes of individuals grappling with musculoskeletal tumors.

Limb Salvage Surgery in a Rare Case of Recurrent Parosteal Osteosarcoma with Vascular Graft Thrombosis

Recurrent parosteal sarcomas with vascular involvement are rare and present unique challenges in their diagnosis and management. We report the case of a 21-year-old woman with parosteal osteosarcoma of the left distal femur, encasing the popliteal vessels. En bloc transarticular resection of the distal femur and popliteal vessels was performed, followed by reconstruction using a modular prosthesis and a saphenous vein autograft for both the artery and vein. On the 1st postoperative day, the patient developed an arterial thrombus requiring reintervention with a jump polytetrafluoroethylene (PTFE) graft. Histopathology confirmed parosteal osteosarcoma. After a disease-free survival of 41 months, the patient experienced local recurrence involving the PTFE graft, leading to graft compression, erosion, and subsequent thrombosis. Despite these complications, limb salvage was possible due to adequate collateral blood supply. This case highlights the feasibility of limb salvage surgery in select cases of parosteal osteosarcoma with vascular involvement.

Current topics and management of head and neck sarcomas

Given the low incidence, variety of histological types, and heterogeneous biological features of head and neck sarcomas, there is limited high-quality evidence available to head and neck oncologists. For resectable sarcomas, surgical resection followed by radiotherapy is the principle of local treatment, and perioperative chemotherapy is considered for chemotherapy-sensitive sarcomas. They often originate in anatomical border areas such as the skull base and mediastinum, and they require a multidisciplinary treatment approach considering functional and cosmetic impairment. Moreover, head and neck sarcomas may exhibit different behaviour and characteristics than sarcomas of other areas. In recent years, the molecular biological features of sarcomas have been used for the pathological diagnosis and development of novel agents. This review describes the historical background and recent topics that head and neck oncologists should know about this rare tumour from the following five perspectives: (i) epidemiology and general characteristics of head and neck sarcomas; (ii) changes in histopathological diagnosis in the genomic era; (iii) current standard treatment by histological type and clinical questions specific to head and neck; (iv) new drugs for advanced and metastatic soft tissue sarcomas; and (v) proton and carbon ion radiotherapy for head and neck sarcomas.

Naturally occurring canine sarcomas: Bridging the gap from mouse models to human patients through cross-disciplinary research partnerships

Fueled by support from the National Cancer Institute's "Cancer Moonshot" program, the past few years have witnessed a renewed interest in the canine spontaneous cancer model as an invaluable resource in translational oncology research. Increasingly, there is awareness that pet dogs with cancer provide an accessible bridge to improving the efficiency of cancer drug discovery and clinical therapeutic development. Canine tumors share many biological, genetic, and histologic features with their human tumor counterparts, and most importantly, retain the complexities of naturally occurring drug resistance, metastasis, and tumor-host immune interactions, all of which are difficult to recapitulate in induced or genetically engineered murine tumor models. The utility of canine models has been particularly apparent in sarcoma research, where the increased incidence of sarcomas in dogs as compared to people has facilitated comparative research resulting in treatment advances benefitting both species. Although there is an increasing awareness of the advantages in using spontaneous canine sarcoma models for research, these models remain underutilized, in part due to a lack of more permanent institutional and cross-institutional infrastructure to support partnerships between veterinary and human clinician-scientists. In this review, we provide an updated overview of historical and current applications of spontaneously occurring canine tumor models in sarcoma research, with particular attention to knowledge gaps, limitations, and growth opportunities within these applications. Furthermore, we propose considerations for working within existing veterinary translational and comparative oncology research infrastructures to maximize the benefit of partnerships between veterinary and human biomedical researchers within and across institutions to improve the utility and application of spontaneous canine sarcomas in translational oncology research.

Osteogenic sarcomas of the hands: A case series with emphasis in its peculiarities and literature review

AIM

To present our experience on osteosarcomas of the hands and review the existing literature pertaining osteosarcomas in this extremely rare location.

METHODS

and results: Seven cases of osteosarcomas of the hands were reviewed, and a literature search of all primary osteosarcomas of the hands was performed. All tumors occurred in adults (mean age, 41 years) and were located mainly around the metacarpophalangeal joints. All patients presented with localized long-lasting pain as main symptom. The mean size at diagnosis was 33 mm. Three tumors were low-grade central osteosarcomas, 1 low-grade central chondroblastoma-like osteosarcoma and 3 high-grade osteosarcomas. All tumors were positive for mouse double-minute 2 homolog (MDM2) immunohistochemistry. Three cases yielded results with fluorescence in-situ amplification for MDM2 (12q15)/CEP12. At last follow-up, one patient with a high-grade osteosarcoma was dead of disease. The literature review revealed similar demographic and site distribution of osteosarcomas within the hands than our series and an unusually high proportion of low-grade central and parosteal osteosarcomas when compared to the proportion of these infrequent neoplasms in the whole skeleton.

CONCLUSIONS

osteosarcomas of hands present in older individuals compared to the population affected by conventional osteosarcomas of all sites. Importantly from a diagnostic, therapeutic and prognostic points of view, around 40% of osteosarcomas of the hands are low-grade osteosarcomas of the central or parosteal types.

Dedifferentiated Low-Grade Osteosarcoma, Outcome with or Without Chemotherapy: A Systematic Review

The treatment of low-grade osteosarcomas is surgical resection with wide margins. In instances of dedifferentiation, a therapeutic paradigm similar to that of conventional high-grade osteosarcoma has not been adequately evaluated in these neoplasms. The main objective of this review was to define whether the addition of chemotherapy to surgical treatment has an impact on the survival of patients with dedifferentiated low-grade osteosarcomas. Secondary objectives were to observe the degree of histological response to neoadjuvant chemotherapy and to describe the percentage of de novo dedifferentiation. A systematic search of articles including dedifferentiated low-grade osteosarcomas, published between 1980 and 2022 was carried out in the PubMed, Cochrane and Scielo databases. A qualitative synthesis of the results was performed. Twenty-three articles comprising 117 patients were included. The survival of patients treated with surgery alone and surgery with chemotherapy was not statistically significant between the two groups. A good histological response was seen in 20% of specimens treated with neoadjuvant chemotherapy. De novo dedifferentiation was seen in approximately a fifth of low-grade osteosarcomas. The evidence available suggests that the addition of chemotherapy does not have an impact on the survival of patients with low-grade dedifferentiated osteosarcomas.

Dedifferentiation in low-grade osteosarcoma: a Japanese Musculoskeletal Oncology Group (JMOG) study

BACKGROUND

Low-grade osteosarcomas, namely parosteal osteosarcoma (POS) and low-grade central osteosarcoma (LGCOS), occasionally dedifferentiate into high-grade malignancy, referred to as dedifferentiation in low-grade osteosarcoma (DLOS). This study aimed to elucidate the clinicopathologic features of DLOS, which are poorly described to date due to the extreme rarity of the disease.

METHODS

A total of 33 patients with DLOS were included. Clinical characteristics, including the diagnostic accuracy of tumor biopsy, multimodal treatments, and clinical course, were retrospectively reviewed. Univariate analysis was performed to identify prognostic factors associated with overall survival (OS) and metastasis-free survival (MFS).

RESULTS

The tumor subtypes comprised 10 cases (30.3%) of LGCOS and 23 cases (69.7%) of POS. The timing of dedifferentiation was synchronous in 25 (75.8%) and metachronous in 8 (24.2%) patients. The rates of preoperative diagnosis of DLOS were 40.0% and 65.4% for core needle biopsy and incisional biopsy, respectively. All patients underwent surgery and 25 patients received perioperative chemotherapy. Of the 13 patients who received neoadjuvant chemotherapy, 11 exhibited a poor histological response. The 5-year OS and MFS rates were 88.1% and 77.7%, respectively. Univariate analysis revealed that local recurrence was associated with poor OS (P < 0.01) and MFS (P < 0.01). Perioperative chemotherapy did not affect OS or MFS.

CONCLUSIONS

The diagnostic accuracy of tumor biopsy for DLOS was lower than that for bone sarcomas, as reported previously. In contrast to conventional osteosarcomas with high chemosensitivity, both histological responses and survival analysis revealed low efficacy of chemotherapy for DLOS.

Does the adherence of distal femur parosteal osteosarcoma to the neurovascular bundle increase the rate of local recurrences?

BACKGROUND

Proximity of tumor to the neurovascular bundle (NVB) makes achieving a wide margin difficult. In low-grade parosteal osteosarcoma (POS), it is not clear whether adherence of tumor to NVB increases the rate of local recurrence (LR). In this study, we evaluated whether tumor adherence to the NVB increases the risk of LR in low-grade POS of the distal femur?

HYPOTHESIS

We hypothesized that if the thin neurovascular barrier (the adventitia of the vessels and the epineurium of the nerve) prevents tumor penetration, the rate of LR should be comparable between the lesions with and without a continuous layer of healthy fatty tissue between the tumor and NVB.

MATERIALS AND METHODS

In a retrospective survey, 30 patients with low-grade POS of the posterior aspect of the distal femur were evaluated for the proximity of mass to NVB. Based on the proximal to distal T1 axial MRI sections, the tumors were divided into two groups including the tumors with an uninterrupted (group A) and interrupted (group B) rim of fatty tissue between the mass and NVB. The rate of LR was compared between the two study groups. The concordance of MRI in detecting NVB adherence was checked with pathology specimen.

RESULTS

Using MRI, we identified 16 cases in group A and 14 cases in group B. The MRI status of fatty rim was concordant with pathology specimen in 96.4% of cases. The mean follow-up period of the two groups was not statistically different (117±27.6 vs. 105.8±29.4 months, respectively, p=0.29). The other baseline characteristics of the two groups were statistically comparable, as well. The rate of LR was 12.5% (2 out of 16 patients) in group A and 14.3% (2 out of 14 patients) in group B (95% CI: 0.142-9.586, p=0.87). The 10-year recurrence-free survival was 87.5% for group A and 85.7% for group B (p=0.9).

DISCUSSION

The absence of a continuous rim of fatty tissue between the tumor and NVB in MRI does not increase the risk of LR in low-grade POS of the distal femur.

LEVEL OF EVIDENCE

IV.

Parosteal osteosarcoma with high-grade transformation and lung metastasis after 12 years: a rare presentation

Parosteal osteosarcoma represents a low-grade, well-differentiated type of cortical surface osteosarcoma with a relatively better prognosis. Systemic metastasis is rare overall and occurs in 10-15% of patients only. Delayed recurrences (>5 years) of parosteal osteosarcoma are even rarer and only few isolated case reports of local recurrence with systemic metastasis occurring beyond 10 years exist in the literature. We present here a case of femoral parosteal osteosarcoma, successfully treated previously, that recurred with high-grade transformation locally and with lung metastasis after 12 years. The patient was managed by lung wedge resection followed by type A1 rotationplasty. Histopathology report confirmed evidence of high-grade transformation (de-differentiation) both locally and at the metastatic site, in view of strong CDK4 and MDM2 nuclear immuno-expression. The present report highlights the importance of long-term follow-up, even for a seemingly less aggressive osteosarcoma variant with identification of a novel pattern of lung metastasis.

JUXTACORTICAL OSTEOSARCOMA: CLINICAL EVOLUTION AND DEDIFFERENTIATION RELATED FACTORS

ABSTRACT Objective: Evaluate risk factors related to clinical evolution and dedifferentiation of parosteal (juxtacortical) osteosarcoma to high-grade osteosarcoma. Methods: Retrospective cohort study performed over a period of 25 years, using data from medical records of patients diagnosed with parosteal osteosarcoma. The data were submitted to statistical analysis by Fisher’s exact test and Student’s t-test. Results: Of the 326 patients treated for osteosarcoma, we identified 17 patients diagnosed with parosteal osteosarcoma. Of these, 4 (23.5%) were not actually diagnosed with parosteal osteosarcoma and 4 did not have the minimum data required for analysis, being excluded from the study. Of the 9 patients studied, we observed that 3 (33.3%) evolved with tumor dedifferentiation to high-grade osteosarcoma. Moreover, 2 (66.7%) had local recurrence and 2 (66.7%) metastases. Conclusion: Age, sex, and the tumor size were not directly related to the dedifferentiation from parosteal osteosarcoma to high-grade osteosarcoma. The most aggressive clinical evolution - presence of local recurrences and metastasis - in parosteal osteosarcoma occurred in tumors with dedifferentiation, however, we cannot associate each other as cause and effect, but as related factors. Level of Evidence IV, Case Series.

Case Report: Metastatic Parosteal Osteosarcoma in a Dog

This case report describes a rare form of malignant bone tumor in an 8-year-old Labrador retriever. This dog initially presented for evaluation of a right distal humeral mass. Radiographs of the right elbow and thorax were performed, revealing a smooth mineralized mass adjacent to the lateral aspect of the distal humerus and a 5mm pulmonary nodule. Computed tomography (CT) of the humerus and thorax showed a smooth mineralized lesion adjacent to the lateral humeral epicondyle, and a right cranial lung lobe nodule with a thin mineral rim. Surgical biopsies of both lesions were diagnostic for parosteal osteosarcoma (POSA). The dog was then treated with stereotactic body radiation therapy (SBRT) which controlled the dog's discomfort for 14 months until he became progressively painful and subsequently had his right forelimb amputated. This case report is the first to document the CT imaging characteristics of a metastatic appendicular POSA in a dog and the first dog described with POSA treated with SBRT. The dog lived for 623 days after histopathologic diagnosis and 849 days after initial presentation with pulmonary metastatic disease.

Parosteal osteosarcoma with a manifestation of subperiosteal low-grade central osteosarcoma

We report the peculiar case of a parosteal osteosarcoma arising beneath the periosteum in a 12-year-old boy. He complained of difficulty in left knee flexion. Plain radiography showed a uniformly dense mineralized mass in the bone cortex and parosteal ossified nodules at the metaphysis and diaphysis of the left distal femur. Periosteal reaction was not evident. Uniquely, plain radiography had a smooth outline and revealed gradually thickening mass toward the center. Histologically, the tumor showed a proliferation of spindle-shaped cells with parallel-oriented dense bone trabeculae and hyaline cartilaginous tissue disclosing mild atypia. The periosteum was inverted along the polypoid mass, but there was no periosteum at the top. Immunohistochemically, the spindle cells, including those at the top of the polypoid mass, and cartilaginous cells were positive for MDM2 and CDK4. MDM2 gene amplification was detected in these cells by fluorescence in situ hybridization. Despite the peculiar feature of plain radiography, the lesion was diagnosed as parosteal osteosarcoma. This case report presents a case of parosteal osteosarcoma arising beneath the periosteum, although it is postulated to arise in the outer layer of the periosteum. The unique radiographic findings in this case suggest an association of parosteal osteosarcoma with vigorous bone growth before closure of the growth plate.

A retrospective analysis of 11 dogs with surface osteosarcoma

While the majority of canine osteosarcomas (OSA) arise from the medullary cavity, a subset arises from the surface of bone. In humans, surface OSA often has a more indolent disease course with better outcomes than medullary OSA. The aim of this retrospective case series was to evaluate the clinical outcome and potential prognostic factors of dogs with surface OSA. Medical records from 11 dogs previously diagnosed with surface OSA were included. Histopathology of cases was evaluated during case review by two veterinary anatomic pathologists. Median progression free interval (PFI) and overall median survival time (OST) were estimated using Kaplan-Meier methods. Intergroup comparisons were performed using log-rank tests. Six dogs were diagnosed with periosteal OSA, 4 dogs with parosteal OSA, and one dog with an unclassified surface OSA. Two dogs were found to have metastatic disease at the time of diagnosis and four developed metastatic lesions after treatment. The median PFI and median OST for all dogs with surface OSA was 425 and 555 days, respectively. The 6 dogs diagnosed with periosteal OSA had a median PFI of 461 days and median OST of 555 days, while the 4 dogs with parosteal OSA had a PFI of 350 days and the OST could not be calculated. Multiple prognostic factors (surgery, systemic adjunctive therapy, elevated alkaline phosphatase at diagnosis, appendicular vs axial location, mitotic count, and tumour grade) were evaluated and none were prognostic for PFI or OST. Dogs with surface OSA appear to have prolonged PFI and OST, consistent with humans with surface OSA.

Pathology of pleomorphic/undifferentiated and dedifferentiated bone neoplasms

Primary malignant bone tumors are uncommon and their accurate classification requires careful correlation of clinical, radiological, and pathologic findings. It is a heterogeneous group of tumors with a wide spectrum of morphology and their biological potential can be of low- or high-grade, depending on their risk for developing metastases. Over the past several decades, the classification of bone sarcomas has remained largely constant. However, some of the tumors have been reclassified and several new entities have emerged. In this review, we will focus on pleomorphic fibrosarcoma/UPS and dedifferentiated bone tumors, discuss their key diagnostic features, differential diagnosis, and their relation to prognosis.

The value of chest and skeletal staging in parosteal osteosarcoma: two-centre experience and literature review

OBJECTIVE

To determine the value of chest and skeletal staging in patients with parosteal osteosarcoma (POS), and the incidence of late local and chest recurrence.

MATERIALS AND METHODS

Retrospective review of patients across two institutions with histological confirmation of POS diagnosed between January 2007 and March 2020. Data collected included age, sex, skeletal location, results of chest CT and whole-body bone scintigraphy (WB-BSc) or whole-body MRI (WB-MRI) obtained at initial diagnosis. The histological tumour grade based on surgical resection specimens was classified as low-grade POS (LG-POS) and dedifferentiated POS (DD-POS). Findings of chest CT and skeletal staging were correlated with tumour grade. Follow-up chest CT and MRI studies were reviewed to determine the rate of late lung metastases and local recurrence.

RESULTS

There were 27 males and 44 females, mean age 33 years (range 12-79 years). The femur (n = 43) and tibia (n = 14) were the most commonly involved bones. From surgical resection histology, 42 (59.2%) were LG-POS and 29 (40.8%) were DD-POS. WB-BSc/WB-MRI showed no skeletal metastases, while 1 case of DD-POS presented with bilateral calcified lung metastases. At follow-up, 7 patients (9.9%) developed lung metastases (mean of 18.9 months, range 10-48 months) from initial presentation, of which all were DD-POS. All but 1 patient who developed subsequent lung metastases had a local recurrence.

CONCLUSIONS

Skeletal staging is unlikely to be of value in POS. Staging chest CT is very unlikely to demonstrate lung metastases in LG-POS and could be limited to DD-POS, particularly at the time of local recurrence.

Parosteal osteosarcoma associated with a low-grade component mimicking well-differentiated liposarcoma: a case report

Parosteal osteosarcomas and well-differentiated liposarcomas are both well-differentiated locally aggressive tumors. They both have simple karyotypes with amplification of the 12q13-15 regions including MDM2 and CDK4 genes. In this report, we describe the case of a parosteal osteosarcoma intertwined with a low-grade component similar to a well-differentiated liposarcoma. The association of a bone component with an adipose component was initially overlooked. We describe the histological, imaging, and molecular characteristics of this tumor stressing the importance of radio-pathological correlation. To our knowledge, this is the second report of a parosteal osteoliposarcoma. Awareness of this rare presentation may allow radiologists and surgeons to recognize the peripheral fatty component as an integral part of the tumor.

A review of imaging of surface sarcomas of bone

Surface lesions of bone are uncommon. Although their imaging features generally mirror those of their intramedullary counterparts, surface lesions may demonstrate distinct characteristics which along with their unusual location present a diagnostic challenge. Surface sarcomas are usually of a lower grade compared with intramedullary variants, leading to differences in management. Osteosarcoma arising from the cortical surface of the bone is termed juxtacortical or surface osteosarcoma and includes three distinct entities: parosteal, periosteal, and high-grade surface osteosarcoma. We also review the features intracortical osteosarcoma, which some authors include under the umbrella term surface osteosarcoma. These lesions exhibit biologic features distinct from those of conventional intramedullary osteosarcoma, which underlines the importance of accurate imaging diagnosis. Periosteal chondrosarcoma and periosteal Ewing sarcoma also have distinctive imaging appearances. The purpose of this article is to review surface sarcomas of bone with regard to their clinical and radiological features and to discuss the differential diagnosis for each condition.

Inflammation and infiltration: can the radiologist draw a line? MRI versus CT to accurately assess medullary involvement in parosteal osteosarcoma

Cancer causes inflammation as it progresses through healthy tissue. The differentiation of tumoral growth from the surrounding inflammatory change is paramount in planning surgeries seeking to preserve function. This retrospective study aims at illustrating how a careful use of imaging (computed tomography (CT)/magnetic resonance imaging (MRI)) can help to draw the line between infiltration and inflammation. Out of 72 cases of parosteal osteosarcoma in our institution we selected 22 which had pretreatment imaging, and out of those, 14 that had both MRI and CT. Using Fisher's exact test, we evaluated the performance of each technique on accurately diagnosing medullary tumor infiltration, using histological analysis as a gold standard. All cases (14/14) demonstrated medullary abnormality on MRI, but only 6/14 (42.9%) demonstrated abnormality on CT. The 8/14 cases with MRI abnormality but no CT abnormality (57.1%) showed inflammation with no tumoral cells present on histological analysis. In the cases where the two examinations showed medullary abnormality (6/14) histology demonstrated tumoral infiltration. MRI demonstrated high sensitivity and negative predictive value, but low specificity and low positive predictive value and accuracy (P=1). CT demonstrated high sensitivity, specificity, high positive and negative predictive values and accuracy (P = 0.000333). MRI is highly sensitive for the detection of medullary abnormality but lacks specificity for tumor invasion. Correlation with CT is recommended in all cases of positive MR to add specificity for tumors. The adequate use of the two imaging methods allows to differentiate between inflammatory change and tumoral infiltration in POS, relevant for surgical planning.

Parosteal Osteosarcoma: A Benign-Looking Tumour, Amenable to a Variety of Surgical Reconstruction

Osteosarcoma arising from cortical surface is classified into parosteal, periosteal and high-grade surface osteosarcoma. Along the spectrum, parosteal osteosarcoma occupies the well-differentiated end. It is a relatively rare disease entity, comprised only 4% of all osteosarcomas and barely reported in the literature. The objective of this study is to describe cases of parosteal osteosarcoma as well as a variety of treatment options amenable to such entity. Six cases of parosteal osteosarcoma were identified based on histopathological reports in a tertiary referral hospital in Jakarta, Indonesia between January 2001 and December 2019. The mean age was 29.8 years old; four of them (66.7%) were male. Distal end of femur was the most commonly involved bone (five cases, 83.3%). The patients were treated with wide excision followed by several different reconstruction methods: replacement with endoprosthesis, extracorporeal irradiation, knee arthrodesis, or prophylactic fixation. One of our patients presented with dedifferentiated component, and therefore was treated by limb ablation. While two cases died of pulmonary metastasis, other patients reported fair to excellent functional outcome.

[Osteoid-forming bone tumors : Morphology and current translational cell biology]

Osteoid osteoma and osteoblastoma are the most important benign osteoid-forming tumors. They grow slowly and are well differentiated. Histologically, the tumor cells show no atypia and no increased mitoses. In typical cases, they can be clearly diagnosed. However, the rare cases on the dividing line between osteoblastoma and osteosarcoma are extremely problematic. In these cases, molecular genetic investigations should contribute to finding the correct diagnosis in the future.Juvenile highly malignant osteosarcoma is the most important malignant osteoid-forming tumor. About 40 years ago, neoadjuvant chemotherapy was introduced for the mostly young patients. This therapy highly significantly improved prognosis. However, a plateau phase was quickly reached and the last several decades have seen no further progress in conventional therapeutic approaches. There is no doubt that further progress can only be achieved on the basis of new molecular genetic and cell biological findings. The target-therapeutic strategies derived from these findings will be discussed in this review.The rare parosteal osteosarcoma and the even rarer periosteal osteosarcoma are mostly not highly malignant tumors that are located on the surface of bone. The parosteal osteosarcoma is usually G1 and the periosteal osteosarcoma G2. Occasionally, the differential diagnosis between a parosteal osteosarcoma and a fibrous dysplasia is difficult. In such rare cases, the detection of GNAS mutations in fibrous dysplasia can prove useful. In contrast to chondromas and chondrosarcomas, periosteal osteosarcomas do not contain IDH1 and IDH2 mutations.

Low-Grade Surface Osteosarcoma of the Temporal Bone in Paediatric Patients: A Case Report and Literature Review

Purpose of the study:

Primary osteosarcoma of the temporal bone is an exceedingly rare pathology in the paediatric population. As of now, only 3 cases have been reported in the English literature. We describe the additional case of a 16-year-old girl with an osteosarcoma of the mastoid bone. This study aims to report a rare paediatric case of low-grade surface osteosarcoma of the temporal bone.

Materials and methods used:

A literature review was performed to better understand paediatric osteosarcomas of the head and neck region, to optimize their investigation, to describe their histopathological and radiological characteristics, and to establish the optimal modalities of medical and surgical treatments. The research of previous published data was done using PubMed and Embase library with the keywords mentioned below.

Results:

The patient presented with a rapidly progressive left retroauricular lesion over a 3-week period. Radiological studies demonstrated aggressive and invasive features. An open biopsy followed and confirmed the diagnosis of a low-grade surface osteosarcoma. In accordance with the multidisciplinary team, we decided to perform a complete surgical resection with wide surgical margins. We did not administer any adjuvant therapies. A control computed tomography (CT) scan obtained 26 months postoperatively still showed no signs of recurrence.

Conclusion:

Osteosarcomas are aggressive malignant neoplasms found in the head and neck region in only 6% to 10% of cases. They represent approximately 1% of head and neck cancers, and these are generally high-grade lesions. Temporal bone involvement is rare, particularly for low-grade lesions in paediatric patients. In addition to reporting the fourth paediatric case of primary temporal bone osteosarcoma, this study describes its specific clinical, histopathological, and radiological findings, to improve the management and the prognostic of patients affected with this particular clinical entity.

A clinical comparison between dedifferentiated low-grade osteosarcoma and conventional osteosarcoma

AIMS

The purpose of this study was to clarify the clinical behaviour, prognosis, and optimum treatment of dedifferentiated low-grade osteosarcoma (DLOS) diagnosed based on molecular pathology.

PATIENTS AND METHODS

We retrospectively reviewed 13 DLOS patients (six men, seven women; median age 32 years (interquartile range (IQR) 27 to 38)) diagnosed using the following criteria: the histological coexistence of low-grade and high-grade osteosarcoma components in the lesion, and positive immunohistochemistry of mouse double minute 2 homolog (MDM2) and cyclin-dependent kinase 4 (CDK4) associated with MDM2 amplification. These patients were then compared with 51 age-matched consecutive conventional osteosarcoma (COS) patients (33 men, 18 women; median age 25 years (IQR 20 to 38)) regarding their clinicopathological features.

RESULTS

The five-year overall survival (OAS) rates in the DLOS and COS patients were 85.7% and 77.1% (p = 0.728), respectively, and the five-year progression-free survival (PFS) rates were 57.7% and 44.9% (p = 0.368), respectively. A total of 12 DLOS patients received chemotherapy largely according to regimens for COS. Among the nine cases with a histological evaluation after chemotherapy, eight showed a poor response, and seven of these had a necrosis rate of < 50%. One DLOS patient developed local recurrence and five developed distant metastases.

CONCLUSION

Based on our study of 13 DLOS cases that were strictly defined by histological and molecular means, DLOS showed a poorer response to a standard chemotherapy regimen than COS, while the clinical outcomes were not markedly different. Cite this article: Bone Joint J 2019;101-B:745-752.

A rare rib lesion due to parosteal osteosarcoma: a case report

Introduction

Masses which develop on the surface of the rib bones are rare. The differential diagnosis includes benign and malignant lesions.

Case presentation

A 23-year-old European woman presented at an out-patient clinic with a 9-month history of a painless swelling on the right posterolateral side of her chest wall. The case reported here is of a very rarely seen parosteal osteosarcoma of the rib that was treated with wide resection and chest wall reconstruction. There was no evidence of local recurrence or distal metastasis after a 1-year follow-up.

Conclusion

Parosteal osteosarcoma is a locally aggressive malignant tumor, and resection with a wide margin is the most appropriate treatment. Correct diagnosis of parosteal osteosarcoma is challenging for an orthopedic surgeon. Although rare, in the differential diagnosis of lesions located on the ribs, parosteal osteosarcoma should be considered and a systematic diagnostic approach should be taken.

Parosteal osteosarcoma of the fibula in a middle-aged patient: A case report

RATIONALE

Parosteal osteosarcoma (PO) is relatively rare, accounting for about 1% of primary malignant bone tumors and 4% of all osteosarcomas. Onset is generally at approximately 20 to 40 years of age; the distal posterior surface of femur is the most common site, accounting for more than 60% cases. However, PO in middle-aged or elderly patients is extremely rare and PO occurring in the fibula is even rarer. To our knowledge, this is the first case of PO occurring in the fibula of a middle-aged adult.

PATIENT CONCERNS

We present a case of a 47-year-old female who had a lateral mass on her left knee for 3 months with no obvious cause.

DIAGNOSES

The patient was initially diagnosed with a proximal left fibula tumor via x-ray scan at a local hospital. Subsequently, osteochondroma was highly suspected through computed tomography (CT) and magnetic resonance imaging (MRI) obtained at our hospital. Finally, the postoperative pathological report confirmed PO.

INTERVENTIONS

She underwent a complete resection of the left fibula tumor and received postoperative adjuvant chemotherapy.

OUTCOMES

The patient recovered well and was discharged on the 10th day after admission. Additionally, there was no evidence of recurrence at the 4-year follow-up after surgery.

LESSONS

In middle-aged or elderly patients, early diagnosis of PO in the fibula is difficult and misdiagnosis or missed diagnosis is common. In clinical practice, PO is uncommon in middle-aged or elderly patients, occurs more rarely in the peroneal bone, and should be carefully identified. CT and MRI are essential for diagnosis, with pathological examination being effective for confirmation. Because of the limited reports of PO of the fibula in middle-aged or elderly adults, the present case raises awareness of this rare condition.

Periosteal Osteosarcoma: A Single-Institutional Study of Factors Related to Oncologic Outcomes

Background

Periosteal osteosarcoma is a rare surface-based variant with a lower propensity to metastasis and better prognosis than conventional osteosarcoma. The literature supporting survival benefit with adjuvant chemotherapy is lacking. Our institutional practice is for chemotherapy to be offered to patients with high-grade disease.

Methods

We conducted a retrospective cohort study of patients managed for periosteal osteosarcoma from 1970 to 2015 analyzing the survival outcomes and assessing for any relationship of survival to patient- or treatment-related factors. 18 patients were included. The study population presented at a mean of 20.8 years and was followed for a mean of 10.7 years. Factors assessed for an association with survival included age, size of tumor, use of chemotherapy, presence of medullary involvement, presence of high-grade disease, local recurrence, and site of disease. Kaplan–Meier survival analysis and Cox proportional hazard regression were performed to calculate the survival rates and to assess for the effect of any factor on survival.

Results

10-year overall survival rate was 77.1%, and 10-year event-free survival rate was 66.4%. No factor was found to have an association with overall or event-free survival.

Conclusion

These findings add to the available evidence which has failed to find any survival benefit from chemotherapy; patients with this rare disease and their families should be counselled regarding the unclear role of chemotherapy in this rare subtype of osteosarcoma.

Zygomatic Arch Parosteal Osteosarcoma in Dogs and a Cat

Parosteal osteosarcoma is a rare, slow-growing tumor most commonly arising from the surface of long bones. Tissue or histological sections from 5 dogs and 1 cat with zygomatic arch masses were examined. Clinical presentations varied from chronic sneezing to facial swelling. Imaging consistently demonstrated osseous proliferation in the area of the zygomatic arch. Histologically, the masses were characterized by well-differentiated fibro-osseous and chondroid components that radiated outward from the periosteum of the zygomatic bone. Cellular atypia and mitotic figures were uncommon. Parosteal osteosarcomas have previously been reported in the skulls of dogs and cats, but only 1 has been reported on the zygomatic arch. Initially, these tumors are of low histologic low grade, but with time, they can show more aggressive behavior and invade the underlying bone.

Dedifferentiated parosteal osteosarcoma of the maxilla: a case report and review of the literature

Background

Parosteal osteosarcomas are usually low-grade tumors, however, sometimes they transform to high-grade tumors, which is named dedifferentiation. This phenomenon has been reported in long bones. Recently, we encountered a patient with dedifferentiated parosteal osteosarcoma occurring in the maxilla. Here, we report a first case of dedifferentiated parosteal osteosarcoma of the head and neck region.

Case presentation

A 45-year-old Japanese woman with a refractory bone lesion in the maxilla presented to our hospital. A biopsy showed atypical spindle cell proliferation involving dedifferentiated high-grade component, which was diagnosed as dedifferentiated parosteal osteosarcoma. Three cycles of neoadjuvant chemotherapy using ifosfamide and pirarubicin were performed followed by sub-total maxillectomy. Histopathological results showed that neoadjuvant chemotherapy was effective for high-grade component. The decision to perform adjuvant chemotherapy (cisplatin and pirarubicin) was made because distant metastasis has been reported, even in cases with dedifferentiated parosteal osteosarcoma in which complete necrosis of high-grade component was achieved due to neoadjuvant chemotherapy. There was no recurrence 15 months after surgery.

Conclusions

Dedifferentiated parosteal osteosarcoma can occur in the head and neck region. Chemotherapy including anthracycline anticancer agent could be effective for high-grade component of dedifferentiated parosteal osteosarcoma.

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.

Osteosarcoma: a comprehensive review

Osteosarcoma (OS) is a relatively rare tumor of bone with a worldwide incidence of 3.4 cases per million people per year. For most of the twentieth century, five-year survival rates for classic OS were very low. In the 1970s, the introduction of adjuvant chemotherapy in the treatment of OS increased survival rates dramatically. The current article reviews the various types of OS and analyzes the clinical and histological features. We also examine historical and current literature to present a succinct review of methods for diagnosis and staging, as well as treatment, and we also discuss some of the future directions of treatment.

Parosteal Osteosarcoma of the Distal Radius Mimicking an Osteochondroma-A Diagnostic Misadventure

We present a case of a parosteal osteosarcoma mimicking an osteochondroma with atypical clinical features, radiographic findings, and histological examination. This report serves to exemplify the importance of recognizing the similarities between these 2 entities and other peculiar features that will help to differentiate between sessile osteochondromas and parosteal osteosarcomas, to prevent misdiagnosis.

Chemotherapy for Bone Sarcoma in Adults

The largest studies of chemotherapy for bone sarcomas are in the pediatric population. Although increasing age is often found to be an adverse prognostic factor in these clinical trials, few studies are aimed at assessing regimens specifically in the adult population. Osteosarcoma and Ewing sarcoma have peak incidences in the pediatric and young adult population but also occur in adults. Chondrosarcoma and giant cell tumor of bone are generally found in adults. In this review, we describe the current status of our knowledge about treating adults with cancers of bone origin. We also describe our experience treating patients in the adult Sarcoma Medical Oncology group at The University of Texas MD Anderson Cancer Center.

[Protocol for the study of bone tumours and standardization of pathology reports]

Primary bone neoplasms represent a rare and heterogeneous group of mesenchymal tumours. The prevalence of benign and malignant tumours varies; the latter (sarcomas) account for less than 0.2% of all malignant tumours. Primary bone neoplasms are usually diagnosed and classified according to the criteria established and published by the World Health Organization (WHO 2013). These criteria are a result of advances in molecular pathology, which complements the histopathological diagnosis. Bone tumours should be diagnosed and treated in referral centers by a multidisciplinary team including pathologists, radiologists, orthopedic surgeons and oncologists. We analyzed different national and international protocols in order to provide a guide of recommendations for the improvement of pathological evaluation and management of bone tumours. We include specific recommendations for the pre-analytical, analytical, and post-analytical phases, as well as protocols for gross and microscopic pathology.

A Pediatric Case of Metastatic Conventional Parosteal Osteosarcoma Treated With Multidrug Chemotherapy

Parosteal osteosarcoma (POS) is conventionally a low-grade sarcoma with limited metastatic potential; however, the tumor occasionally transforms into a high-grade dedifferentiated POS, which commonly metastasizes to distant organs. The present report describes a rare pediatric case of conventional POS with no dedifferentiated component yet had multiple pulmonary metastases at initial diagnosis. Following limb-sparing surgery and osteosarcoma-oriented neoadjuvant chemotherapy, the patient received total resection of pulmonary metastases. Despite no treatment for pulmonary recurrence 1 year after adjuvant chemotherapy, the patient is alive with stable disease 4 years and 6 months after the initial diagnosis.

Treatment of Bone Tumors

In this article, the authors summarize the state of the art and future potential in the management of Osteosarcoma, Ewing's sarcoma, and Chondrosarcoma. They cover systemic therapy, surgical therapy, and radiotherapy, along with targeted therapies to inhibit signal transduction pathways. They discuss staging and the role of imaging evaluation to provide an overview of bone tumor treatment. Images presenting pathologic-radiologic correlations are included.

Custom-made intercalary endoprosthetic reconstruction for a parosteal osteosarcoma of the femoral diaphysis: A case report

The present report describes a case of a 44-year-old female patient who presented with a palpable mass of the left thigh. A diagnosis of parosteal osteosarcoma (POS) at the femoral diaphysis was made following a diagnostic workup. Previous reports of long bone diaphyseal POS are rare. A long diaphyseal segment of the femur containing the tumor was resected along with a healthy margin of soft tissues, and the damaged bone was reconstructed with a custom-made intercalary endoprosthesis. Subsequent pathological examination of the surgical sample confirmed the diagnosis of POS. No local recurrence or distant metastasis was observed, and the patient had a positive Musculoskeletal Tumor Society score of 28/30 (93.3%) at the 28-month post-surgery follow-up. The present study describes the clinical, radiological, and pathological features of this rare type of osteosarcoma.

The prognostic and therapeutic factors which influence the oncological outcome of parosteal osteosarcoma

The aim of this study was to evaluate the prognostic and therapeutic factors which influence the oncological outcome of parosteal osteosarcoma.

A total of 80 patients with a primary parosteal osteosarcoma were included in this retrospective study. There were 51 females and 29 males with a mean age of 29.9 years (11 to 78).

The mean follow-up was 11.2 years (1 to 40). Overall survival was 91.8% at five years and 87.8% at ten years. Local recurrence occurred in 14 (17.5%) patients and was associated with intralesional surgery and a large volume of tumour. On histological examination, 80% of the local recurrences were dedifferentiated high-grade tumours. A total of 12 (14.8%) patients developed pulmonary metastases, of whom half had either a dedifferentiated tumour or a local recurrence. Female gender and young age were good prognostic factors. Local recurrence was a poor prognostic factor for survival. Medullary involvement or the use of chemotherapy had no impact on survival.

The main goal in treating a parosteal osteosarcoma must be to achieve a wide surgical margin, as inadequate margins are associated with local recurrence. Local recurrence has a significant negative effect on survival, as 80% of the local recurrences are high-grade dedifferentiated tumours, and half of these patients develop metastases.

The role of chemotherapy in the treatment of parosteal osteosarcoma is not as obvious as it is in the treatment of conventional osteosarcoma. The mainstay of treatment is wide local excision.

Cite this article: Bone Joint J 2015;97-B:1698–1703.

Surface osteosarcoma: Clinical features and therapeutic implications

INTRODUCTION

Surface osteosarcoma are rare variant of osteosarcoma that include parosteal osteosarcoma, periosteal osteosarcoma and high grade surface osteosarcoma. These lesions have different clinical presentation and biological behavior compared to conventional osteosarcoma, and hence need to be managed differently.

GOAL

The aim of this study is to analyze the clinico-pathological features and outcome of a series of surface osteosarcoma in an attempt to define the adequate treatment of this rare entity.

PATIENT AND METHOD

It is a retrospective and bicentric study of 18 surface osteosarcoma that were seen at the KASSAB's Institute and SAHLOUL Hospital from 2006 to 2013. The authors reviewed the clinical and radiologic features, histologic sections, treatments, and outcomes in this group of patients.

RESULTS

Seven patients were male (38.9%) and 11 were female (61.1%) with mean age of 25 years (range from 16 to 55 years). Eleven lesions were in the femur and 7 in the tibia. We identified 11 parosteal osteosarcoma (six of them were dedifferentiated), 3 periosteal osteosarcoma and 4 high grade surface osteosarcoma. Six patients had neoadjuvant chemotherapy and all lesions had surgical resection. Margins were wide in 15 cases and intra lesional in 3 cases. Histological response to chemotherapy was poor in all cases. The mean follow up was 34.5 months. Six patients (33.3%) presented local recurrence and 8 patients (44.4%) presented lung metastases. Six patients (33.3%) died from the disease after a mean follow up of 12 months (6-30 months); all of them had high grade lesions.

CONCLUSION

Histological grade of malignancy is the main point to assess in surface osteosarcoma since it determines treatment and prognosis. Low grade lesions should be treated by wide resection, while high grade lesions need more aggressive surgical approach associated to post operative chemotherapy.

GNAS mutations are not detected in parosteal and low-grade central osteosarcomas

Parosteal osteosarcoma, low-grade central osteosarcoma, and fibrous dysplasia share similar histological features that may pose a diagnostic challenge. The detection of GNAS mutations in primary bone tumors has been useful in clinical practice for diagnosing fibrous dysplasia. However, the recent report of GNAS mutations being detected in a significant proportion of parosteal osteosarcoma challenges the specificity of this mutation. As the number of cases reported in this study was small we set out to determine if these results could be reproduced. We studied 97 formalin-fixed paraffin-embedded low-grade osteosarcomas from 90 patients including 62 parosteal osteosarcomas, of which MDM2 amplification was detected in 79%, 11 periosteal osteosarcomas and 24 low-grade central osteosarcoma samples. The mutational status of GNAS was analyzed in codons p.R201, p.Q227, and other less common GNAS alterations by bidirectional Sanger sequencing and/or next generation sequencing using the Life Technologies Ion Torrent platform. GNAS mutations were not detected in any of the low-grade osteosarcomas from which informative DNA was extracted. Our findings therefore support prior observations that GNAS mutations are highly specific for fibrous dysplasia and occur rarely, if ever, in parosteal and other low-grade osteosarcomas.

Clinical Epidemiology of Low-Grade and Dedifferentiated Osteosarcoma in Norway during 1975 and 2009

Purpose. To describe epidemiological, clinical characteristics and treatment outcomes of low-grade osteosarcoma (LGOS), including dedifferentiated osteosarcoma (DLGOS). Method. We analysed a nationwide cohort comprised of patients with histologically verified LGOS and DLGOS between 1975 and 2009, based on registry sources supplemented with clinical records from hospitals involved in sarcoma management. Results. Fifty-four patients were identified, 12 of whom had DLGOS. The annual incidence for all patients was 0.3 per million, with the peak incidence in the third decade of the life. Fifteen patients experienced local relapses during follow-up and ten developed metastatic diseases, including three at primary diagnosis. Patients with DLGOS dominated the metastatic relapse group. The five-year sarcoma-specific survival rate was 91%, with no documented improvement over time. Free margin following surgical resection of the primary tumour had a positive impact on survival. As expected, both local relapse and metastasis during follow-up were associated with an unfavourable outcome. Radiotherapy predicted poor survival due to the selection of high-risk patients in need of such treatment. Neither higher age nor axial tumour localisation was adverse prognostic factors. Conclusion. LGOS has an excellent prognosis when surgically resected with a free margin; however, LGOS has the potential to dedifferentiate and metastasize with a poor outcome.