Extraosseous Osteosarcoma Research Articles

Extraosseous osteosarcoma of the larynx: an unusual tumor managed with radical surgery – case report

Introduction and importance: Extraosseous osteosarcoma (EOO) is a malignant tumor that arises in soft tissue without affecting bone or periosteum but produces osteoid, osseous, or chondroid material. It is a very rare malignancy that accounts for approximately less than 1% of all tissue sarcomas and ~2–4% of all osteosarcomas. EOO in the head and neck region is extremely rare; however, in the larynx, it is exceptional, with only one case reported worldwide in the literature to date. Case presentation: A 72-year-old male with no personal history of interest in the current condition presented with dysphonia, hoarseness, and dyspnea for 6 months. A flexible nasofibrolaryngoscopy (FNFL) and computed tomography (CT) scan exhibited a glottic tumor with a lumen obstruction of 90%. An endoscopic resection was performed, reporting an EOO, osteoblastic, and ulcerated type. During follow-up, tumoral persistence was detected, leading to the decision to perform a definitive radical treatment with a total laryngectomy. Clinical discussion: Its presentation in the head and neck region is exceptional, with only a few isolated cases reported in the literature. Available data on treatment recommendations have emphasized the importance of timely surgical intervention with adjuvant radiation therapy if necessary for the head and neck. Conclusion: Extraosseous osteoblastoma of the larynx is an extremely rare and infrequent disease. Correct diagnosis and oncological surgical management of this disease are essential for optimal and even curative treatment of the patient.

Large-Scale assessment of ChatGPT's performance in benign and malignant bone tumors imaging report diagnosis and its potential for clinical applications

ObjectiveThis study was designed to delve into the complexities involved in diagnosing of benign and malignant bone tumors and to assess the potential of AI technologies like ChatGPT in improving diagnostic accuracy and efficiency. The study also explores the few-shot learning as a method to optimize ChatGPT's performance in specialized medical domains such as benign and malignant bone tumors diagnosis. MethodsA total of 1366 benign and malignant bone tumors-related imaging reports were collected and diagnosed by 25 experienced physicians. The gold standard of diagnosis was established by combining clinical, imaging and pathological principles.These reports were then input into the ChatGPT model which underwent a few-shot learning method to generate diagnostic results. The diagnostic results of the physicians and the AI model were compared to evaluate the performance of ChatGPT. An experiment was conducted to assess the influence of different radiologist's reporting styles on the model's diagnostic performance. Furthermore, in-depth analysis of misdiagnosed cases was carried out, categorizing diagnostic errors and exploring possible causes. ResultsThe diagnostic results generated by ChatGPT showed an accuracy of 0.73, sensitivity of 0.95, and specificity of 0.58. After few-shot learning, ChatGPT demonstrated significant improvement, achieving an accuracy of 0.87, sensitivity of 0.99, and specificity of 0.73, bringing it much closer to the level of physician diagnostics. In an experiment analyzing the influence of the radiologist's reporting style, the model demonstrated higher sensitivity when interpreting reports written by high-level radiologists. In 56 benign cases, ChatGPT misdiagnosed them as malignant. Among these, 35 benign lesions- fibrous dysplasia and osteofibrous dysplasia- were incorrectly identified as metastatic tumors or osteosarcomas; 8 cases of myositis ossificans were wrongly diagnosed as extraosseous osteosarcoma. 7 cases of giant cell tumor of bone at the end of long bone were misdiagnosed as osteosarcoma by intermediate doctors. Chondroblastoma was misdiagnosed as malignant tumor in 6 cases −2 osteosarcoma and 4 chondrosarcoma-In this study, 23 osteosarcoma cases were misdiagnosed by ChatGPT as osteomyelitis; Chondrosarcoma was misdiagnosed as fibrous dysplasia or aneurysmal bone cyst in 8 cases. Four cases of spinal chordoma were misdiagnosed as spinal tuberculosis. ConclusionOur findings highlight the potential of ChatGPT in the diagnosis of benign and malignant bone tumors, offering advantages like enhanced efficiency and a reduction in missed diagnoses. However, the necessity of collaborative interactions between physicians and ChatGPT in practical settings was underscored. With an examination into AI's capacity in benign and malignant bone tumors diagnosis, this study lays the groundwork for future AI advancements in medicine. Additionally, the benefits of few-shot learning in fine-tuning ChatGPT applications in specialized fields were also demonstrated.

Imaging diagnosis and differential diagnosis of extraskeletal osteosarcoma

ObjectiveThe aim of this study was to investigate the clinical, imaging and pathological features of extraskeletal osteosarcoma (EOS) and to improve the understanding of this disease and other similar lesions.MethodsThe data for 11 patients with pathologically confirmed extraosseous osteosarcoma, including tumour site and size and imaging and clinical manifestations, were analysed retrospectively.ResultsSix patients were male (60%), and 5 were female (40%); patient age ranged from 23 to 76 years (average age 47.1 years). Among the 11 patients, 7 had clear calcifications or ossification with different morphologies, and 2 patients showed a massive mature bone tumour. MRI showed a mixed-signal mass with slightly longer T1 and T2 signals in the tumour parenchyma. Enhanced CT and MRI scans showed enhancement in the parenchyma. Ten patients had different degrees of necrosis and cystic degeneration in the mass, 2 of whom were complicated with haemorrhage, and MRI showed “fluid‒fluid level” signs. Of the 11 patients, five patients survived after surgery, and no obvious recurrence or metastasis was found on imaging examination. One patient died of lung metastasis after surgery, and 2 patients with open biopsy died of disease progression. One patient died of respiratory failure 2 months after operation. 2 patients had positive surgical margins, and 1 had lung metastasis 6 months after operation and died 19 months after operation. Another patient had recurrence 2 months after surgery.ConclusionThe diagnosis of EOS requires a combination of clinical, imaging and histological examinations. Cystic degeneration and necrosis; mineralization is common, especially thick and lumpy mineralization. Extended resection is still the first choice for localized lesions. For patients with positive surgical margins or metastases, adjuvant chemoradiotherapy is needed.

Ossifying fasciitis: A rare phenomenon and a mimicker for malignancy

Abstract Introduction/Objective Ossifying fasciitis is a relatively rare variant of nodular fasciitis. However, it can mimic malignant lesions, particularly extraosseous osteosarcoma. The purpose of this report is to describe a florid case of ossifying fasciitis with an unusual clinical course in a 17-year-old male. Methods/Case Report A 17-year-old male underwent surgery at an outside hospital for a soft tissue mass in his left upper thigh that had been present for over two years. Pathology was consistent with a benign myofibroblastic tumor. No bone formation was present in the biopsy. Next generation sequencing showed a COL1A1::USP6 gene fusion. The patient was then referred to our institution due to rapid recurrence and unresolving infection at the surgery site. An ultrasound revealed a mass measuring 3.3 x 2.7 x 1.3 cm at the surgery site. The patient subsequently underwent wide surgical resection of the mass.Gross inspection and sectioning of the specimen revealed a well-defined, encapsulated firm calcified lesion with approximately 30% soft pink gelatinous cut surfaces. Microscopically, the lesion was composed of spindle-shaped fibroblastic cells and extensive osteoblastic activity with a zonated transition from immature osteoid to immature woven bone. The diagnosis of ossifying fasciitis was rendered. Results (if a Case Study enter NA) NA Conclusion Rapidly growing lesions can be misinterpreted as sarcomas. Careful microscopic examination and correlation with clinical and radiologic data is critical for accurate diagnosis. Molecular data can be helpful in difficult cases.

Practical Management of Adult Ultra-Rare Primary Retroperitoneal Soft Tissue Sarcoma: A Focus on Perivascular Epithelioid Tumours and Extraosseous Ewing Sarcoma.

With the exception of well-differentiated liposarcoma, dedifferentiated liposarcoma, leiomyosarcoma, solitary fibrous tumour, malignant peripheral nerve sheath tumour, and undifferentiated pleomorphic sarcoma, the majority of the ≈70 histologic subtypes of retroperitoneal sarcoma are defined as 'ultra-rare' sarcomas, with an incidence of ≤1-5/1,000,000 persons/year. For most of these ultra-rare RPS subtypes, diagnosis and treatment follows international guidelines for the management of more common RPS histologies, with en bloc surgical resection as the mainstay of curative treatment, and enrolment in clinical trials where possible. Because the treatment of RPS is heavily driven by histology, the surgeon must be familiar with specific issues related to the diagnosis and management of ultra-rare sarcoma subtypes. Expert radiological and surgeon reviews are required to differentiate similarly presenting tumours where surgery can be avoided (e.g., angiomyolipoma), or where upfront systemic therapy is indicated (e.g., extraosseous Ewing's sarcoma). Thus, the management of all retroperitoneal sarcomas should occur at a sarcoma referral centre, with a multidisciplinary team of experts dedicated to the surgical and medical management of these rare tumours. In this focused review, we highlight how diagnosis and management of the ultra-rare primary RPS histologies of malignant perivascular epithelioid cell tumour (PEComa), extraosseous Ewing sarcoma (EES), extraosseous osteosarcoma (EOS), and rhabdomyosarcoma (RMS) critically diverge from the management of more common RPS subtypes.

A Rare Case of Extraosseous Osteosarcoma (EOS) of Parotid Gland.

Extraosseous osteosarcoma is a rare malignant soft tissue neoplasm, and extraosseous osteosarcoma of the parotid gland is very rare. It has a very aggressive course, and there are no standardized treatment guidelines.We report the case of a 20 year old male patient who presented with history of right neck swelling since 6 years for which he had undergone right parotid surgery 5 years ago. The final histopathological report indicated that the mass was a pleomorphic adenoma. One year after the first surgery, the patient experienced recurrence of swelling over the operated site, and the size of the swelling has been increasing gradually since then. He was evaluated clinically, and a large mass was noted over the upper aspect of the right upper neck, extending to the occipital and parotid regions. An MRI scan was done which showed a 12 × 10 × 8cm lesion centred in the right parotid gland, involving paraspinal muscles, C1-C2 vertebrae and extending into the parapharyngeal space. FNAC of the lesion showed features of pleomorphic adenoma. The patient underwent a complete excision of the tumour. The patient's post-operative period was uneventful. The final histopathological report of the patient was extraosseous osteosarcoma of the parotid gland. The patient was referred for adjuvant radiotherapy. He has been on regular follow-up for the past 6 months and has shown no sign of recurrence.EOS is an extremely rare tumour of the head and neck region which often requires extensive surgical resection with or without adjuvant radiotherapy. It has a high rate of local recurrence and a very low disease free survival. Such patients should be kept on a close follow-up.

A case of extraosseous intradural osteosarcoma of the spine in a dog

AbstractA 9.5‐year‐old labrador presented with signs of progressive C1–C5 myelopathy. Magnetic resonance imaging of the cervical spine revealed a broad‐based, jagged and partially ill‐defined intradural mass lesion at the level of C3–C4 cervical vertebra. Decompressive spinal surgery was performed and the removed mass was sent for histopathological examination that identified an intradural extraosseous osteosarcoma. This very rare canine spinal tumour appears to arise predominantly in the cervical spine and occurs with no predisposing factors. It should be considered as a differential diagnosis for spinal tumours.

Intraperitoneal extraosseous osteosarcoma: a case report and literatures review

BackgroundTo investigate the clinical imaging manifestations, diagnosis and treatment of intraperitoneal extraosseous osteosarcoma.Case presentationA 52-year-old male patient with intraperitoneal extraosseous osteosarcoma was retrospectively analyzed. He suffered from left lower abdominal pain accompanied by mass for 6 months. On abdominal CT scan, multiple patchy and banded calcification were found. The largest is about six centimeters in diameter and underwent mass resection. Postoperative pathology revealed retroperitoneal osteosarcoma. The reported intraperitoneal extraosseous osteosarcoma was analyzed and the related literature was reviewed. Two years after operation, the patients had recurrence of the tumors and invaded sigmoid colon, peritoneum and bladder. Palliative operation was performed to remove the tumors in the bladder and transverse colostomy was performed. The patients were followed up by telephone and died 2 months after the second operation.ConclusionsIntraperitoneal extraosseous osteosarcoma has a low incidence and has no specific imaging features. Surgical resection is the main treatment and the prognosis is poor.

Anterior abdominal wall extraosseous osteosarcoma, occurring 40 years after para-aortic irradiation

Extraskeletal osteosarcomas (OSs) are highly malignant soft tissue tumours associated with a poor prognosis. Only a few records of these rare aggressive neoplasms have been reported in the literature.We describe...

A rare case of extraosseous osteosarcoma of the parotid gland

Primary extraosseous osteosarcomas (EOO) are very rare and extraosseous osteosarcoma of the parotid gland is even rarer. When they occur, EOO pursues a very aggressive cause. The consequence of the rarity of this malignancy and its aggressive course is that treatment guidelines are not yet standardized. We present a case of extraosseous osteosarcoma of the parotid gland we encountered in our practice. Keywords: Extraskeletal Osteosarcoma, extraosseous osteosarcoma, Parotid gland, salivary gland, Cancer

First Case of Mesenteric Extraosseous Osteosarcoma in Australia

An Extraosseous Osteosarcoma (EOS) arising in mesentery is exceedingly rare with only six previous cases documented in English literature worldwide. This manuscript describes the clinical, radiological and histological features of the first known case of mesenteric EOS in Australia. The collation of additional cases will help ameliorate our understanding of its clinical course and guide appropriate management, planning and prognostication.

Unusual presentation of primary extra osseous osteosarcoma: As breast abscess

Primary extra osseous osteogenic sarcoma is one of the rarest forms of malignant tumor of the breast. It can arise as a result of osseous metaplasia of a preexisting neoplasm or from a none-phylloides sarcoma of a previously normal breast. Due to its rarity, natural history and optimal treatment methods remain unclear. A 60-year-old patient presented to the surgical casualty with large breast abscess. Abscess wall histology revealed an osteosarcoma of the breast. Left total mastectomy with axillary clearance was performed. Histology and subsequent imunohistochemical studies confirmed the diagnosis of osteogenic sarcoma without lymph nodal metastasis. The patient was referred to the oncologist for further management. Rare types of breast tumors can be presented as breast abscess. Incision and drainage together with wall biopsy help to exclude associated sinister pathologies. Diagnosis of primary osteosarcoma of the breast was made using histological and immunohistochemical findings once the possible primary from the sternum and ribs were excluded. Treatment is as for sarcomas affecting other locations and should comprise a multidisciplinary approach.

CORR Insights(®): Should High-grade Extraosseous Osteosarcoma Be Treated With Multimodality Therapy Like Other Soft Tissue Sarcomas?

O rthopaedic oncology is a specialty defined by uncertainty. Although we are able to diagnose sarcoma subtypes reliably and recommend treatment plans, the reality is that even tumors with the same name can act dramatically differently. Therefore, the clinician must use many details about the individual scenario—grade, histologic subtype, size, depth, location, stage, and patient demographics—to make a logical guess as to the anticipated behavior of the diagnosed condition. As described by Fan and colleagues [3], extraosseous osteosarcoma is a representative example of a common dilemma in orthopaedic oncology: How do we select the most appropriate management strategy when we are unable to accurately predict the natural history or response to treatment in a rare cancer? The first attempt at understanding a rare tumor is by a simple descriptive case report or case series to reveal general observations about the patients in which the tumor occurs, the common features of presentation, the treatments attempted, and the observations on oncologic outcomes (survival and recurrence). The current study is the most recent in a line of such case series. In attempt to view this problem from a novel perspective, Fan and colleagues question if extraosseous osteosarcoma behaves more similarly to a soft tissue sarcoma than a skeletal osteosarcoma. This is a reasonable approach, and has worked well for most subtypes of highgrade soft tissue sarcoma as their biologic aggressiveness, response to treatment, and patient outcomes are similar. They found that some features, such as a therapeutic response to radiation, are more characteristic of soft tissue sarcoma than skeletal osteosarcoma. As the authors note, the heterogeneity of treatment increases the difficulty in interpretation, as there was This CORR Insights is a commentary on the article ‘‘Should High-grade Extraosseous Osteosarcoma Be Treated With Multimodality TherapyLikeOther Soft Tissue Sarcomas?’’ by Fan and colleagues available at: DOI: 10.1007/s11999-015-4463-y. The author certifies that he, or a member of his immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/ licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors andClinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. The opinions expressed are those of thewriters, and do not reflect the opinion or policy of CORR or The Association of Bone and Joint Surgeons. This CORR Insights comment refers to the article available at DOI: 10.1007/s11999-0154463-y. B. J. Miller MD, MS (&) Department of Orthopaedics and Rehabilitation, University of Iowa, 200 Hawkins Dr, 01015 JPP, Iowa City, IA 52242, USA e-mail: benjamin-j-miller@uiowa.edu CORR Insights Published online: 27 August 2015 The Association of Bone and Joint Surgeons1 2015

Should High-grade Extraosseous Osteosarcoma Be Treated With Multimodality Therapy Like Other Soft Tissue Sarcomas?

Extraosseous osteosarcoma is rare, and the most appropriate therapy is unclear because there are few studies regarding its treatment. The effectiveness of radiation and chemotherapy remains uncertain owing to conflicting results in previous reports. To review our experience with contemporary multimodality treatment, we asked: (1) What is the disease-specific survival and local relapse-free survival? (2) Does American Joint Commission on Cancer (AJCC) stage, tumor size, or location relate to disease outcome? (3) Does radiation therapy improve local control or survival? (4) Do doxorubicin and ifosfamide improve local control or survival? Between 1990 and 2012, we treated 40 patients for localized, high-grade extraosseous osteosarcoma. In this retrospective study, we could determine the status of 36 patients (90%) either to death or for a minimum of 24 months of followup; four (10%) were lost to followup before 24 months. There were 11 patients with AJCC Stage IIA and 25 with Stage III disease. All patients underwent wide surgical excision. Of the patients with Stage IIA disease, four received radiation and none received chemotherapy. Of the patients with Stage III disease, six received radiation, seven were treated with chemotherapy, and six received radiation and chemotherapy. During the study period, high-dose doxorubicin and ifosfamide was the preferred chemotherapy regimen for patients younger than 60 years with normal cardiac and renal function. Local relapse-free survival and disease-specific survival were determined by Kaplan-Meier analysis using a prospectively maintained institutional database supplemented by information from the institutional tumor registry. The Cox proportional hazard model was used to determine the effect of various factors on local recurrence and patient survival. At 5 years, local relapse-free survival was 47% (95% CI, 27%-64%), and disease-specific survival was 53% (95% CI, 35%-68%). In multivariate analysis, AJCC stage, which depends on tumor size, was the strongest predictor of local relapse-free survival (hazard ratio [HR] = 0.17, p = 0.02), while tumor depth was the best predictor of disease-specific survival (HR = 5.6, p = 0.02). Radiation improved local relapse-free survival (HR = 0.30, p = 0.03) but not disease-specific survival in multivariate analysis. A regimen of doxorubicin and ifosfamide was associated with better local relapse-free survival for patients with Stage III disease (HR = 0.16, p = 0.04) but not disease-specific survival (HR = 0.32, p = 0.08). With the limited number of patients in our study, it appears that extraosseous osteosarcoma behaves differently than osteosarcoma of bone. Multimodality treatment that includes doxorubicin and ifosfamide-based chemotherapy, radiation, and surgery may be a valid therapeutic strategy for Stage III disease, but larger, prospective studies will be needed to verify our preliminary observations. Level III, therapeutic study.

Radiation-induced Extra-osseous Osteosarcoma—A Case Report and Review of Literature

Carcinogenesis associated with exposure to radiation is widely known, first reported more than 100 years ago in 1902 by Friben and in 1907 by Porter and White [16]. Exposure to therapeutic doses of radiation have also been shown to be associated with an increased risk of a second cancer, although the precise risk remains unknown. Sarcomas are a rare, but recognized, complication of RT for breast carcinoma, and are associated with poor prognosis. The first description of a bone sarcoma after RT of a breast tumor was reported by Beck in 1922, and Warren and Sommer in 1936 [2] reported a soft tissue sarcoma in the breast treatment volume. The long term incidence of sarcoma after radiation therapy for breast cancer is 0.2 % for 10 years [3]. In 1948, Cahan et al. [2] defined the criteria for the diagnosis of radiation-induced sarcoma. EOO is a soft tissue tumor that produces osteoid, bone or chondroid material without attachment to the skeleton as determined by imaging modalities [4]. Wilson reported the first case of EOO in 1941 and so far only around 300 cases have been reported in the English literature [6]. Most reported cases of osteosarcoma of the chest wall following radiation therapy for breast cancer arise from the chest wall skeletal structures [11]. We describe a rare case of EOO involving the chest wall musculature, after radiation therapy for breast cancer.

A case of intradural osteosarcoma of the spine

Background contextIntradural-extramedullary spinal tumors and extradural osteosarcomas are both rare entities. Only one case of primary intradural-extramedullary osteosarcoma of the spine has been previously reported. This is the second reported case. PurposeTo describe a case of primary intradural-extramedullary osteosarcoma of the spine associated with rapid clinical deterioration. Study designCase report of a 70-year-old woman who presented with a constellation of neurologic symptoms. MethodsReview of patient files, radiographic studies, surgical images, histopathology, and relevant literature. ResultsThe patient underwent tumor debulking but exhibited rapid, postsurgical, functional deterioration and died within 6 weeks. This case and the only previous case of its kind both occurred in individuals with a remote history of iophendylate (Myodil) myelogram. ConclusionsPrimary intradural-extramedullary extraosseous osteosarcoma of the spine is an exceedingly rare entity with no established management approach. Iophendylate myelography may be implicated in the etiology of this tumor type.

Extra osseous osteosarcoma of the retroperitoneum: An unusual entity

Extra-osseous osteosarcomas constitute about 1-1.2% of all osteosarcomas. The most common sites are the extremities, thorax, and the abdomen. Retroperitoneal osteosarcomas are rare and very few cases have been reported. They are similar in their biology to high grade soft tissue sarcomas. R0 resection appears to be the best possible treatment for these tumors. All three variants of conventional osteosarcoma--osteoblastic, chondroblastic, and fibroblastic have been described in these tumors. Chemotherapy has been attempted with adriamycin-based regimens with poor results. Unlike extremity osteosarcomas, these tumors have been found to be chemoresistant. The 5 year survival has ranged from a dismal 12% to about 25%. We report a 46-year-old male who presented with a kidney tumor infiltrating the descending colon, but turned out to be an extra osseous osteosarcoma. An R0 resection was done and adjuvant chemotherapy given.

Primary paratesticular osteosarcoma: A case report.

Extraosseous osteosarcoma originating from paratesticular soft tissue is an extremely rare type of malignant tumor. With the exception of the present study, only one other case of osteosarcoma originating from paratesticular soft tissue has previously been reported. A 52-year-old man presented with a painless scrotal swelling and palpable mass. The patient underwent left orchiectomy with the diagnosis of testicular tumor. Pathological examination was suggestive of osteosarcoma without any different histological components. The postoperative course of the patient was uneventful, and the patient is currently free of disease.

Extraosseous osteosarcoma in the neck

Extraosseous osteosarcoma arising in the head and neck region is an exceptional finding, with a few isolated cases informed in the literature. We report a new case of a large high-grade extraosseous osteosarcoma located in the neck. A 74 year-old woman with a tumor on the right side of the neck was treated by complete surgical resection. The histopathological diagnosis was osteoblastic extraosseous osteosarcoma. PET-CT scan disclosed no evidence of disease in other areas. Patient received adjuvant radiotherapy and after 3 months of follow-up tumor activity was detected in the cavernous sinus and the patient died of disease one month later. Extraosseous osteosarcoma in head and neck region is exceptional, and incisional biopsy is the only method to establish a diagnosis and the one to differentiate it from other bone-producing soft tissue tumors. Surgery is the gold standard for treatment of extraosseous osteosarcoma.

PROTEOMIC PROFILES OF DESMOID TUMORS AND OSTEOSARCOMA OF BONE AND SOMATIC SOFT TISSUE

DESMOID TUMORS AND HIGH GRADE OSTEOSARCOMAS OF BONE AND SOMATIC SOFT TISSUE HAVE DISTINCT PROTEOMIC PROFILESProteomic analysis of recurrent but non metastasizing desmoid tumors, and osteosarcoma (OS) with known metastatic potential occurring in older individuals was performed to identify potential predictive marker proteins for drug resistance and prognosis. Archived samples from nineteen desmoid tumors and fourteen primary osteosarcoma occurring in soft tissue, bone were collected following IRB approval. Five micron thick sections were obtained from paraffin blocks of tumor and scraped, digested and analyzed by mass spectrometry. Protein abundances determined by spectral counting and used for hierarchical cluster analysis. Increase in HSP70, clusterin, emelin, creatine kinase B and carbonic anhydrase noted predominantly in OS. Results were validated for myoglobin and clusterin by immunohistochemical stains.. Proteins at higher abundance in OS relate to oxidative stress and hypoxia. HSP90 and clusterin may be markers of aggressive extraosseous osteosarcoma and may be indicative of drug resistance. The absence of these proteins in desmoids support their being considered benign locally recurrent tumors.