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.

Bizarre parosteal osteochondromatous proliferation in the distal ulna where the lesion is continuous with the medullary cavity: a case report.

BACKGROUND: Bizarre parosteal osteochondromatous proliferation (BPOP) is a rare benign bone tumor, it is also called "Nora's lesion". The lesion is characterized by heterotopic ossification of the normal bone cortex or parosteal bone. The etiology of BPOP is unclear and may be related to trauma. In most BPOPs, the lesion is not connected to the medullary cavity. Here we report an atypical case, characterized by reversed features compared to the typical BPOP, which demonstrated continuity of the lesion with the cavity. CASE PRESENTATION: An 11-year-old female child had a slow-growing mass on her right wrist for 8 months with forearm rotation dysfunction. Plain X-rays showed an irregular calcified mass on the right distal ulna, and computed tomography (CT) showed a pedunculated mass resembling a mushroom protruding into the soft tissue at the distal ulna. The medulla of this lesion is continuous with the medulla of the ulna. A surgical resection of the lesion, together with a portion of the ulnar bone cortex below the tumor was performed, and the final pathology confirmed BPOP. After the surgery, the child's forearm rotation function improved significantly, and there was no sign of a recurrence at 1-year follow-up. CONCLUSION: It is scarce for BPOP lesions to communicate with the medullary cavity. However, under-recognition of these rare cases may result in misdiagnosis or inappropriate treatment thereby increasing the risk of recurrence. Therefore, special cases where BPOP lesions are continuous with the medulla are even more important to be studied to understand better and master these lesions. Although BPOP is a benign tumor with no evidence of malignant transformation, the recurrence rate of surgical resection is high. We considered the possibility of this particular disease prior to surgery and performed a surgical resection with adequate safety margins. Regular postoperative follow-up is of utmost importance, without a doubt.

Bizarre parosteal osteochondromatous proliferation (Nora lesion) involving the spine: a case report and systematic review.

Bizarre parosteal osteochondromatous proliferation (BPOP), also termed Nora lesion, is a rare, benign tumor most often located in the hands and feet. We herein present the second reported case of BPOP affecting the spine, an uncommon location. One year after surgical excision, the patient was pain-free and showed no evidence of recurrence. We reviewed a total of 323 cases of BPOP among 101 articles, providing the first systematic update on the latest knowledge of BPOP. The age of patients with BPOP ranges from 3 months to 87 years, peaking in the second and third decades of life. The hands are the most common location of BPOP (58.39%), followed by the feet (20.81%). Imaging features play a key role in the diagnosis of BPOP, but histopathologic diagnosis remains the gold standard. Differential diagnosis of BPOP should be based on the epidemiologic and clinical features as well as clinical examination findings. Surgical resection is the most extensively used treatment for BPOP. Recurrence is common (37.44%) and can be treated with re-excision. This article can deepen our understanding of BPOP and will be helpful for the diagnosis and treatment of BPOP in clinical practice.

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.

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.

A unique presentation of the rare Nora's lesion, symptomatic bizarre parosteal osteochondromatous proliferation: A case report.

Bizarre parosteal osteochondromatous proliferations, also known as Nora's lesions, are rare benign tumors with a high recurrence rate. They are often difficult to identify because of their similar appearance to other tumors. We describe a 25-year-old healthy female patient with bizarre parosteal osteochondromatous proliferations in an uncommon location on the pelvic ilium, presenting with unique clinical findings of abdominal pain and femoral paresthesia and showing atypical radiographic findings. To the best of our knowledge, this is one of the very few cases ever reported in the literature of Nora's lesion in this particular location and possibly the first case ever with this specific presentation. The lesions' radiographic images, combined orthopedic and general surgery procedures, and histological analysis are detailed. The patient's continued 4-year follow-up has demonstrated no symptoms or evidence of recurrence.

Bizarre Parosteal Osteochondromatous Proliferation (Nora's Lesion) Affecting Carpal Bones of the Hand in a Middle-Aged Female: A Case Report.

A 45-year-old woman complained of left wrist pain and swelling for two years accompanied by limited dorsiflexion. Plain X-rays revealed an abnormal bony mass in the carpal bones, further evaluated using computed tomography and magnetic resonance imaging. Upon confirmation of the benign nature surgical excisional biopsy of the lesion, the histopathology confirmed the diagnosis of Bizarre parosteal osteochondromatous proliferation (BPOP). The patient has remained pain-free and actively involved in her routine for the past two years. BPOP, affecting the carpal bones of the hand, are exceptionally rare occurrence. Attentive preoperative evaluation helps in diagnosis and to initiate measures to avoid recurrence.

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.

Bizarre parosteal osteocondromatous proliferation (BPOP) of the acromion with soft tissue recurrence.

Bizarre parosteal osteochondromatous proliferation (BPOP) is a benign but rare periosteal-originating chondrogenic tumor. It commonly arises from the hands and feet. It is slow-growing and often presents as a painless lump. On imaging, the mass is well-marginated and almost always remains contiguous with the cortical bone. Histologically, the lesion is composed of a disorganized admixture of fibrous tissue, bone, and cartilage with bizarre features. Treatment is surgical and local recurrence is common contiguous with bone. This case report demonstrates an uncommon acromial BPOP with the first reported recurrence not contiguous with the underlying cortex.

Bizarre parosteal osteochondromatous proliferations of the temporal region: a case report.

Bizarre parosteal osteochondromatous proliferations (BPOPs) are distinct clinical-pathological entities that demonstrate combinations of atypical-appearing osseous and chondromatous tissues. These lesions are usually reactive in nature. Histopathologically, 'bizarre' cartilage is a characteristic feature of this lesion. BPOPs usually represent slow-growing painless bony hard protuberances that arise from the surface of affected bone cortices, typically the metacarpals, metatarsals, and phalanges. The occurrence of these lesions in the skull and jaws is sporadic. This case report highlights the clinical presentation, histopathological characteristics, and management of BPOP arising from the supraorbital rim in a 61-year-old female patient.

Parosteal Lipoma.

Teaching Point: Recognizing the distinct imaging features of parosteal lipoma.

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.

Bizarre Parosteal Osteochondromatous Proliferation (Nora's Lesion) Of the Second Proximal Phalanx Encasing the Flexor Tendon of the Foot: A Case Report.

Introduction: Bizarre Parosteal Osteochondromatous Proliferation (BPOP) is a rare benign lesion commonly referred to as Nora's lesion. It typically affects adults in their 20s-30s. Due to its aggressive local invasion, it can be confused with some malignant tumors, including chondrosarcoma. Nora's lesion can be diagnosed radiographically, and its diagnosis is confirmed with an excisional biopsy. Case Report: A 40-year-old Bahraini male complained of swelling over the metatarsal head of the second digit, increasing in size over a year. He also complained of a reduced range of motion of the second toe and a pins-and-needles sensation affecting the entire toe. Plain X-ray, computed tomography, and magnetic resonance imaging were done, showing findings suggestive of bizarre parosteal osteochondromatous. The lesion was encasing the flexor tendon of the second digit. He was treated with surgical excision, and histopathology confirmed the diagnosis of BPOP. Conclusion: We report on a rare presentation of BPOP in the second proximal phalanx of a male in his 40 s. The patient underwent a wide local excision, and the diagnosis was confirmed with histopathology.

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 Lipoma Overlying an Osteochondroma of the Hyoid Bone: A Case Report and Literature Review.

Parosteal lipomas and osteochondromas of the head and neck are uncommon benign tumors, constituting a small fraction of lipoma and bone tumor cases. We present a unique case of a 66-year-old male with a parosteal lipoma overlying an osteochondroma in the anterior midline neck, causing dysphagia. Surgical excision confirmed the diagnosis, and a literature review revealed similar cases predominantly adjacent to the mandible or calvaria. This case emphasizes the need to have parosteal lipoma and osteochondroma on the differential diagnosis for patients presenting with a firm mass of the central neck, especially with a history of trauma. Laryngoscope, 2023.

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.

Unraveling the Mystery of Parosteal Lipoma of the Distal Femur: A Rare Case Report.

Introduction: Among all the primary bone tumors and all the type of lipomas, parosteal lipomas stand for <0.1% and 0.3%, respectively, which mostly consists of fully developed adipose tissue with or without a bony component. Patients with this tumor usually have bony lesions (59.2%), necessitating a differential diagnosis of malignant tumors. Case Report: Here, we analyze a case report of a 9-year-old boy, who developed a parosteal lipoma in the distal femur. A massive, well-defined, lobulated, mostly fat-intensity lesion of 10 cm by 6 cm by 8 cm was seen on an magnetic resonance imaging scan of the right distal femur. After the lump was removed, the pathologically reveals a parosteal lipoma without any malignant changes. Conclusion: Finally, it should be noted that parosteal lipomas are less common neoplasias with no known malignant potential. Since these tumors can be removed with mild impact to nearby structures, the lower limb's functionality is kept intact.

Parosteal Osteosarcoma of the skull: Pathophysiological and imaging review.

Parosteal Osteosarcoma (POS) is a well-differentiated low-grade malignant sarcoma occurring at the bone surface. POS of the skull is exceedingly rare, with only 4 temporal bone cases reported in modern literature. This tumor may resemble a multitude of entities, hence identifying it is critical. This may be achieved through a combination of clinical, histopathological, and imaging diagnostic techniques. POS may recur locally or dedifferentiate, the latter having a worse prognosis. This review aims to update the reader regarding the management of the rare Parosteal Osteosarcoma located in the skull bone.

Bizarre parosteal osteochondromatous proliferation: an educational review.

Bizarre parosteal osteochondromatous proliferation (BPOP) is a surface-based bone lesion belonging to the group of benign chondrogenic tumors. The aim of this review is to familiarize the readers with imaging features and differential diagnosis of BPOP, also addressing pathological presentation and treatment options. The peak of incidence of BPOP is in the third and fourth decades of life, although it can occur at any age. Hands are the most common location of BPOP (55%), followed by feet (15%) and long bones (25%). On imaging, BPOP appears as a well-marginated mass of heterotopic mineralization arising from the periosteal aspect of the bone. Typical features of BPOP are contiguity with the underlying bone and lack of cortico-medullary continuity, although cortical interruption and medullary involvement have been rarely reported. Histologically, BPOP is a benign bone surface lesion characterized by osteocartilaginous proliferation with disorganized admixture of cartilage with bizarre features, bone and spindle cells. Differential diagnosis includes both benign-such as florid reactive periostitis, osteochondroma, subungual exostosis, periosteal chondroma and myositis ossificans-and malignant lesions-such as periosteal chondrosarcoma and surface-based osteosarcoma. Treatment consists of surgical resection. Local recurrences are common and treated with re-excision.Critical relevance statement Bizarre parosteal osteochondromatous proliferation is a benign mineralized mass arising from the periosteal aspect of bone cortex. Multi-modality imaging characteristics, pathology features and differential diagnosis are here highlighted to familiarize the readers with this entity and offer optimal patient care.