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.

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

INTRODUCTION: conventional parosteal osteosarcoma is an uncommon malignant bone tumor, comprising 4% of all osteosarcomas. Although rare, parosteal osteosarcoma is the most common type of osteosarcoma of the bone surface. We present the clinical, histological and imaging characteristics of a rare histologic variant of a parosteal osteosarcoma, review the literature and emphasize the importance of radio-pathological correlation as well as the interpretation of a representative biopsy in order to obtain the correct diagnosis. CASE REPORT: a 36-year old woman began her condition one year prior to admission to the hospital with increased volume in the left knee and pain. Image studies showed a juxtacortical heterogeneous tumor localized on the posterior surface of the distal femoral metaphysis. An incisional biopsy was performed, with the diagnosis of a Parosteal Osteosarcoma and a wide surgical resection was undertaken. According to the findings of the surgical specimen, the diagnosis of a Parosteal Osteosarcoma with low grade chondrosarcoma and liposarcoma components was made. The knowledge of this rare parosteal osteosarcoma variant can lead the orthopedic oncologists to avoid overlooking the adipose component and provide adequate surgical margins. CONCLUSION: we present the clinical, histological and imaging characteristics of a Parosteal Osteosarcoma with low grade liposarcoma and chondrosarcoma components.

INTRODUCCIÓN: el osteosarcoma parosteal convencional es un tumor óseo maligno poco común, que comprende el 4% de todos los osteosarcomas. Aunque es poco común, el osteosarcoma parosteal es el tipo más común de osteosarcoma de la superficie ósea. Presentamos las características clínicas, histológicas y de imagen de una variante histológica rara de un osteosarcoma parosteal, revisamos la literatura y enfatizamos la importancia de la correlación radio-patológica, así como la interpretación de una biopsia representativa para obtener el diagnóstico correcto. REPORTE DE CASO: mujer de 36 años inició su cuadro un año antes de su ingreso al hospital con aumento de volumen en rodilla izquierda y dolor. Los estudios de imagen mostraron una tumoración heterogénea yuxtacortical localizada en la superficie posterior de la metáfisis femoral distal. Se realizó biopsia incisional, con diagnóstico de osteosarcoma parosteal y se realizó resección quirúrgica amplia. De acuerdo con los hallazgos de la pieza quirúrgica se realizó el diagnóstico de osteosarcoma parosteal con componentes de condrosarcoma y liposarcoma de bajo grado. El conocimiento de esta rara variante de osteosarcoma parosteal puede llevar a los ortopedistas oncólogos a considerar otros componentes y proporcionar márgenes quirúrgicos adecuados. CONCLUSIÓN: presentamos las características clínicas, histológicas y de imagen de un osteosarcoma parosteal con componentes de liposarcoma y condrosarcoma de bajo grado.

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.

Prognostic Factors Influencing Survival and Oncological Outcome in Patients with Parosteal Osteosarcoma.

This study aimed to evaluate the significance of radiological (magnetic resonance imaging [MRI]) findings, surgical, and previous interventions on prognosis with oncological and functional outcome in patients with parosteal osteosarcoma (POS). Twenty-seven patients (8 male/19 female) who were operated with the diagnosis of primary POS in our institution were retrospectively reviewed. The epidemiological data, biopsy method, misdiagnosis/improper interventions, and delay in diagnosis were noted. The lesions' maximum circumferential extension, maximum longitudinal extension, intramedullary involvement, and neurovascular extensions in MRI sections were evaluated, and the resection type (segmental intraarticular/segmental intercalary/hemicortical), reconstruction type (biologic/non-biologic), and surgical margins were noted. Functional and oncological results at the last follow-up were assessed. The mean age was 31.6 (12-73) years, and mean follow-up was 80.8 (24-270) months. Intramedullary involvement percentage was related with maximum circumferential extension percentage and maximum longitudinal extension. (p = 0.006, p = 0.005) The intramedullary involvement ratio of ≤ 10% suggested no recurrence or metastasis. The neurovascular encasement was related to metastatic disease, deep infections, and complication related surgeries (p = 0.017, p = 0.002, p = 0.005). The most common resection type was segmental intraarticular resection (63%). The maximum circumferential extension percentage, the maximum longitudinal extension of the lesion, intramedullary involvement percentage, and neurovascular encasement had lower MSTS scores (p = 0.003, p = 0.028, p = 0.038, p = 0.022). The mean MSTS score was 81.1% (60-100%). The 5-year overall survival was 96.3%, local recurrence-free survival was 77.2%, and metastasis-free survival was 69.4%. The lesions' extent of intramedullary involvement, neurovascular bundle proximity, and maximum periosteal circumferential extension on MRI should be considered when planning the surgery.

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.

Parosteal osteosarcoma of the temporal bone: Case report.

Parosteal osteosarcomas (POS) are well-differentiated low-grade malignant sarcomas that are located on the surface of the bone. POS of the temporal bone is exceptionally rare, with less than a hand full of cases present in modern literature. Here, we report a POS of the temporal bone found incidentally and with an uncharacteristic presentation. We also review the unique imaging and histopathological findings of this entity and discuss why developing a broad differential diagnosis and proceeding with early intervention are considered imperative in this disease.

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.

Synchronous Primary Parosteal Osteosarcoma and Primary Mediastinal Germ Cell Tumour with Atypical Mycobacterial Infection - A Rare Phenomenon: A Case Report.

Mediastinal germ cell tumours are a rare group of extragonadal germ cell tumours with less than 5% prevalence of all germ cell tumours. Primary mediastinal germ cell tumours themselves account for 16-36% of the extragonadal germ cell tumours. Along the spectrum of osteosarcoma, parosteal osteosarcoma is a well-differentiated surface osteosarcoma with a prevalence of 4% of all osteosarcoma. As such synchronous primary parosteal osteosarcoma and primary mediastinal germ cell tumour are exceedingly rare. This leads to complexity in determining the most appropriate chemotherapy for two different types of tumours and its potential side effects of reduced immunity leading to potential secondary infection. Here we report a case of a 16-year-old boy who presented with synchronous primary osteosarcoma and primary mediastinal germ cell tumour, complicated with atypical mycobacterial infection post-operatively. Additionally, we discuss our choice of chemotherapy and the management of the atypical mycobacterial infection.

Periosteal Fasciitis With Unusual Radiologic Features Harboring a Novel STAG1::USP6 Fusion Gene.

Periosteal fasciitis is a subtype of nodular fasciitis originating from the periosteum. The diagnosis can be challenging and requires radiologic-pathologic correlation. Advances in molecular analysis confirmed that nodular fasciitis and its related lesions harbor a USP6 gene rearrangement with one of the several potential partners. Herein, we report a case of periosteal fasciitis with metaplastic bone formation detected incidentally during a radiologic survey for breast carcinoma. Radiologic examination revealed a 2.4 cm, heterogeneous, avidly enhancing lesion of the right femoral distal metaphysis concerning for low-grade periosteal chondrosarcoma. Histological examination of a core needle biopsy revealed a tumor composed of bland spindle cells with myofibroblastic and osteoblastic phenotypes admixed with immature bone and cartilaginous elements. Molecular analysis revealed a novel STAG1::USP6 fusion that helped arrive at the right diagnosis and further expands the molecular profile of USP6-associated neoplasms.

Bizarre Parosteal Osteochondromatous Proliferation (Nora's Lesion) of the Foot: A Case Report and Literature Review of Nora's Lesion of the Foot.

Bizarre parosteal osteochondromatous proliferation (BPOP) or Nora's lesion is a rare, benign, but locally aggressive tumor. We present a case of a 45-year-old patient with progressive swelling of his toe for four years, pain, and difficulty with shoe wear. The lesion was excised after adequate evaluation and the resection histopathology was compatible with Nora's lesion. There was no local recurrence at 24 months of follow-up. Nora's lesion can be effectively treated by complete surgical excision or en bloc resection. Though rare, Nora's lesion should be considered in the differential diagnoses of osteogenic and/or chondrogenic overgrowths in the bones of feet such as subungual exocytosis, osteochondroma, chondrosarcoma, periosteal chondroma/chondrosarcoma, and parosteal osteosarcoma.

Sarcomas of fat and bone: a case report.

Osteosarcomas are the most common primary malignant bone tumors and are classified by the WHO into several intramedullary and surface subtypes. One of these is the rare parosteal osteosarcoma. Liposarcomas are the second most common soft tissue sarcoma and are classified into several types ranging from intermediate to high grade tumors. In one of our recent patients we found an unusual combination of a parosteal osteosarcoma and a large fatty component, which fluorescence-in-situ-hybridization revealed as liposarcoma. Radiologists, pathologists, and surgeons should consider the possibility of bone and soft tissue malignancies consisting of different components, as this may be of paramount importance for oncologically complete resection.

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.

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.

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.

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.

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.

Nail Salon a Potential Source of a Rare Mycobacterium Fortuitum Infection In Proximal Tibia Megaprosthesis? A Case Report.

Mycobacterium Fortuitum (M. Fortuitum) is a type of opportunistic pathogen commonly found in water/soil and belongs to the nontuberculosis mycobacteria (NTM) family. Prosthetic joint infection due to M. Fortuitum is extremely rare. We present a case of a 21-year-old female with an infection following a radical resection of the proximal tibia due to a parosteal osteosarcoma.

Parosteal Osteosarcoma of the Proximal Phalanx of a Finger.

Osteogenic sarcoma of the hand is very rare and fewer than 50 cases have been reported. There are only 2 previously reported cases of parosteal osteosarcoma involving the phalanges. We report a primary parosteal osteosarcoma involving the proximal phalanx of the right middle finger in a 20-year-old woman, which was managed by ray amputation. There was no evidence of local recurrence or systemic metastasis in the postoperative follow-up period of 2 years.