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.

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

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

[Parosteal osteosarcoma of the femur and salvage surgery with intercalary prosthesis. Experience in a third level unit and surgical technique]. / Osteosarcoma parostal de fémur y cirugía de salvamento con prótesis intercalar. Experiencia en una unidad de tercer nivel y técnica quirúrgica.

INTRODUCTION: parosteal osteosarcoma is an extramedullary malignant bone tumor in which cells produce osteoid, represents less than 5% of all osteosarcomas, it occurs predominantly in women between the second and fourth decade of life. It is often located in the distal region of the femur and proximal tibia. Clinically it presents with increased volume and thigh or knee pain. Due to its low incidence and clinical features, a clinical case of femoral parosteal osteosarcoma is presented, with description of the surgical technique performed. CASE REPORT: a 14-year-old female presented with a 6-month history of increased volume and right thigh pain. Radiological studies revealed a bone lesion with malignant characteristics, for which she was sent to third-level hospital where oncology study protocol was set up; consisting in two percutaneous biopsies of the lesion with Jamshidi needle, which were histopathology reported as negative for malignant cells. The pulmonary high-resolution computed tomography showed metastasis and a Tc-99m MDP bone scintigraphy showed increased osteoblastic activity in the right femoral shaft. Given the results, is confirmed the need of en-bloc resection and intercalary prosthesis implantation with adjuvant chemotherapy. CONCLUSION: the intercalary prosthesis is a suitable therapeutic option in limb-salvage surgery for patients with femoral parosteal osteosarcoma.

INTRODUCCIÓN: el osteosarcoma parostal es un tumor óseo maligno extramedular en el cual las células tumorales producen osteoide. Representa menos de 5% de los osteosarcomas. Se presenta predominantemente en la mujer, entre la segunda y cuarta década de la vida. Su localización más frecuente es la región distal del fémur y proximal de la tibia. Clínicamente, se manifiesta con aumento de volumen y dolor en muslo o rodilla. Debido a su baja incidencia y características clínicas, se presenta un caso clínico de osteosarcoma parostal femoral con descripción de la técnica quirúrgica realizada. CASO CLÍNICO: femenino de 14 años edad con cuadro clínico caracterizado por aumento de volumen y dolor en muslo derecho de seis meses de evolución. Se realizaron radiografías de fémur derecho, encontrando lesión ósea con características compatibles de malignidad, por lo que es enviada a unidad de tercer nivel para iniciar protocolo oncológico; se realizan dos biopsias percutáneas con aguja de Jamshidi, ambas con reporte histológico negativo para células malignas. En tomografía pulmonar de alta resolución se observó presencia de metástasis y la gammagrafía ósea con Tc99 reportó actividad osteoblástica en fémur derecho. Se decide tratamiento con resección en bloque y colocación de prótesis intercalar más quimioterapia adyuvante. CONCLUSIÓN: la prótesis intercalar resulta una opción terapéutica adecuada en la cirugía de salvamento de extremidad para pacientes con diagnóstico de osteosarcoma parostal femoral.

Parosteal osteosarcoma of the thumb: A case report and literature review.

Parosteal osteosarcoma (PO) is a rare malignant tumor arising from the surface of the bone. Locations in the hand are even more exceptional. This low-grade osteosarcoma shows non-specific clinical and radiological presentation, making diagnosis challenging. Moreover, histologic examination is extremely difficult and can easily lead to misdiagnosis. We report the case of a 21-year-old woman who presented PO of the right thumb, initially diagnosed as a "benign exostosis" 9 years previously. En-bloc resection followed by reconstruction using a free corticocancellous iliac crest autograft provided good esthetic and functional outcome. No recurrence occurred at 2 years' follow-up. Our literature review confirmed the rarity of PO of the hand, with only 8 cases reported in the past 60 years. Amputation was the main treatment, but some authors reported limb-sparing surgery. The present result and those in the literature review support conservative surgery when feasible, with little recurrence and better functional and esthetic results. These rare tumors should not be misdiagnosed, and should be treated in specialized centers to optimize outcome.

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.

[Dedifferentiated diaphyseal juxtacortical osteosarcoma of ulna with metastasis to the lung]. / Osteosarcoma parostal desdiferenciado en diáfisis de cúbito metastásico a pulmón.

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

El osteosarcoma parostal desdiferenciado es una variante en la cual un osteosarcoma de alto grado coexiste con un osteosarcoma parostal. Se presenta el caso de un paciente femenino de 20 años; acudió con seis meses de evolución de dolor y limitación funcional en el antebrazo derecho sin causa aparente; se le realizaron radiografías, donde se observó una lesión tumoral en la diáfisis del cúbito derecho. A la exploración física, presentó dolor a la palpación en la diáfisis del cúbito y limitación a la pronosupinación. La tomografía axial computada de tórax reveló enfermedad metastásica en el lóbulo superior del pulmón izquierdo. Se le efectuó una biopsia incisional de la tumoración en el cúbito derecho, con reporte de osteosarcoma parostal desdiferenciado. Por ello, inició manejo con quimioterapia neoadyuvante con cisplatino y doxorrubicina hasta completar tres ciclos. El tratamiento quirúrgico consistió en resección intercalar de la diáfisis del cúbito derecho más reconstrucción de injerto autólogo microvascularizado de la diáfisis del peroné derecho y estabilización del injerto con placa de compresión dinámica (DCP) 3.5 mm y placa tercio de caña. En el mismo procedimiento se le efectuó metastasectomía pulmonar por toracoscopía. El reporte histopatológico postquirúrgico, con necrosis de 100%. Actualmente, la paciente se encuentra asintomática, sin datos de actividad tumoral. El osteosarcoma parostal desdiferenciado es una patología rara, pero que se debe sospechar como diagnóstico diferencial ante un osteosarcoma parostal; se debe tener en cuenta que esta enfermedad puede generar metástasis por su patrón desdiferenciado. Es importante planificar un tratamiento quirúrgico que permita una adecuada reconstrucción funcional, siempre teniendo en cuenta el principio oncológico.

Osteosarcoma parostal desdiferenciado en diáfisis de cúbito metastásico a pulmón / Dedifferentiated diaphyseal juxtacortical osteosarcoma of ulna with metastasis to the lung

Resumen: El osteosarcoma parostal desdiferenciado es una variante en la cual un osteosarcoma de alto grado coexiste con un osteosarcoma parostal. Se presenta el caso de un paciente femenino de 20 años; acudió con seis meses de evolución de dolor y limitación funcional en el antebrazo derecho sin causa aparente; se le realizaron radiografías, donde se observó una lesión tumoral en la diáfisis del cúbito derecho. A la exploración física, presentó dolor a la palpación en la diáfisis del cúbito y limitación a la pronosupinación. La tomografía axial computada de tórax reveló enfermedad metastásica en el lóbulo superior del pulmón izquierdo. Se le efectuó una biopsia incisional de la tumoración en el cúbito derecho, con reporte de osteosarcoma parostal desdiferenciado. Por ello, inició manejo con quimioterapia neoadyuvante con cisplatino y doxorrubicina hasta completar tres ciclos. El tratamiento quirúrgico consistió en resección intercalar de la diáfisis del cúbito derecho más reconstrucción de injerto autólogo microvascularizado de la diáfisis del peroné derecho y estabilización del injerto con placa de compresión dinámica (DCP) 3.5 mm y placa tercio de caña. En el mismo procedimiento se le efectuó metastasectomía pulmonar por toracoscopía. El reporte histopatológico postquirúrgico, con necrosis de 100%. Actualmente, la paciente se encuentra asintomática, sin datos de actividad tumoral. El osteosarcoma parostal desdiferenciado es una patología rara, pero que se debe sospechar como diagnóstico diferencial ante un osteosarcoma parostal; se debe tener en cuenta que esta enfermedad puede generar metástasis por su patrón desdiferenciado. Es importante planificar un tratamiento quirúrgico que permita una adecuada reconstrucción funcional, siempre teniendo en cuenta el principio oncológico.

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

Parosteal osteosarcoma of mandible: A rare case report.

With the exception of multiple myelomas, osteosarcoma is the most frequently occurring primary malignant bone tumor with an overall incidence of 1:100,000/year. It has greatest predilection for the metaphyses, most frequently femur and tibia. However, osteosarcomas affecting the craniofacial bones are infrequent. Two main types: intramedullary and juxtacortical varieties are seen. Juxtacortical variety is further subdivided into periosteal and parosteal variants. Due to its rarity, only 13 cases of parosteal osteosarcoma have been reported till date. A 35-year-old male patient with affected postirradiated mandible is being reported as the 14th case of this kind with its unique benign presentation and less aggressive nature.

What are the Oncologic and Functional Outcomes After Joint Salvage Resections for Juxtaarticular Osteosarcoma About the Knee?

BACKGROUND: Joint salvage surgery for patients with juxtaarticular osteosarcoma remains challenging, especially when the tumor invades the epiphysis. Because patients are surviving longer with current chemotherapy regimens, it is advantageous to retain native joints if possible, especially in young patients. However, the results using joint-preserving tumor resections in this context have not been well characterized. QUESTIONS/PURPOSES: (1) What are the functional outcomes after limb salvage surgery at a minimum of 3 years? (2) What are the oncologic outcomes? (3) Is joint salvage surgery for epiphyseal tumors associated with an increased risk of local recurrence compared with metaphyseal tumors not invading the epiphysis? (4) What are the complications associated with joint salvage surgery? METHODS: Between 2004 and 2013, we treated 117 patients with juxtaarticular osteosarcoma; of those, 43 (38%) were treated with joint salvage surgery, and 41 (95%) of the 43 patients are included in our study. The other two (5%) were lost to followup before 3 years (mean, 4.4 years; range, 3-11 years,). During the period in question, we generally performed joint salvage surgery in these patients when they had a favorable response to chemotherapy, did not have a pathologic fracture or extrusion of the tumor into the joint, and did not have a whole-epiphyseal osteolytic lesion, a large mass, or obvious neurovascular involvement. This report is a followup of an earlier study; the current study includes an additional nine patients, and additional followup of a mean of 19 months for the patients included in the earlier report. We ascertained overall survival and survival free from local recurrence which was estimated using the Kaplan-Meier method, functional status of the limb which was evaluated using the Musculoskeletal Tumor Society (MSTS)-93 scoring system, and recorded reconstructive complications including infection, fracture, skin necrosis, and nonunion. We compared oncologic and functional outcomes between patients with (n = 28) and without tumor extension to epiphysis (n =13). We also compared oncologic and functional outcomes among patients with different adjuvant treatments including microwave ablation (n = 11), cryoablation (n = 12), and navigation-assisted osteotomy (n = 5). Complications were tallied using records from our institutional database. RESULTS: The overall Kaplan-Mayer survival rate was 82% (95% CI, 104-128 months) at 5 years. The overall Kaplan-Meier survivorship from local recurrence was 91% at 5 years (95% CI, 115-133 months). Three patients had a local recurrence, but none had local recurrence in or close to the remaining epiphysis. The MSTS scores ranged from 22 to 30 points, with a median of 28. There were no differences in survival rate, local recurrence, or MSTS scores between patients with a tumor that did not invade the epiphysis and those in whom the tumor did invade the epiphysis. There were differences in MSTS scores among patients with epiphyseal tumor extension in which different adjuvant techniques, including microwave ablation, cryoablation, and navigation-assisted osteotomy, were used. Additional surgical procedures were recorded for 10 patients (24%). Osteonecrosis of the residual epiphysis was detected 13 patients (31%). CONCLUSIONS: Our findings suggest it is possible to salvage joints in selected patients with juxtaarticular osteosarcoma around the knee. The patients who have a favorable response to chemotherapy are the best candidates for this approach. Future studies might explore the role of adjuvant techniques of microwave ablation and cryoablation, particularly when the tumor invades the epiphysis, and whether resections can be facilitated with navigation. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Recurrence of juxtacortical chondrosarcoma arising on the rib.

Juxtacortical chondrosarcoma developing on the surface of a bone is quite rare. We report a case of juxtacortical chondrosarcoma arising on the fourth rib of a 76-year-old man. Intraregional tumor resection was performed, but local recurrence was detected after 6 months. The patient underwent wide resection including the ribs, and reconstruction of the thoracic wall. He was released with a good prognosis after a year. This case emphasizes the importance of biopsy analysis before surgery to carefully evaluate tumor spread in the cartilage and performing wide resection even if the tumor is easily separated from the bone.

Precise resection and biological reconstruction under navigation guidance for young patients with juxta-articular bone sarcoma in lower extremity: preliminary report.

BACKGROUND: It is a challenge to perform a joint-preserving resection for young patients with juxta-articular bone sarcomas. We determined whether osteotomy under image-guided navigation make joint-saving resection possible for juxta-articular lesions while adhering oncological principles. METHODS: Between June 2008 and July 2010, joint-preserving limb salvage surgeries were performed on 9 patients with juxta-articular bone sarcomas under navigation guidance. Computed tomography/magnetic resonance imaging fusion images were used for real-time navigation. Eight lesions located around the knee and 1 in hip. Six tumors extend to and 3 beyond the epiphyseal line. Planned osteotomy under image-guided navigation was employed for achieving clear surgical margin while maximizing host tissue preservation. All tumors were en bloc removed and intercalary defect were reconstructed by combination of allograft with vascularized fibula graft. All specimens were examined for resection margin. Patients were followed up for an average of 25.2 months for evaluating of functional and oncology outcomes. RESULTS: Entire joint were preserved in 6 patients and part of joint were saved in another 3 patients. The mean registration error for navigation was 0.40 mm (range, 0.31 to 0.62 mm). Clear surgical margin was obtained in all specimens. The average closest distance between the osteotomy line and tumor edge was 9.6 mm (range, 6 to 14 mm). Entire joint cartilage was preserved in 6 patients and portion of joint were saved in 3 patients (2 in proximal tibia, 1 in distal femur). No patient experienced local recurrence. Two patients developed lung metastasis. One died of disease and the other underwent metastasectomy and had no evidence of disease at the most recent follow-up. All reconstruction was in situ with the Musculoskeletal Tumor Society average score of 26.7 at final follow-up. CONCLUSIONS: With careful patient selection, image navigation-assisted surgery made it possible to resect the bone exactly as planned in length and orientation in the magnetic resonance imaging image, yielding a clear margin and preserving the entire or part of the articular cartilage in joint-sparing limb salvage procedures for treating skeletally immature patients with juxta-articular bone sarcomas. LEVEL OF EVIDENCE: Level IV--therapeutic study.

[Parosteal osteosarcomas: unusual findings]. / Osteosarcomas parostales: resultados infrecuentes.

OBJECTIVE: To study and evaluate the unusual findings in the natural history of parosteal osteosarcomas. Parosteal osteosarcomas are well-differentiated tumours of low grade malignancy, but may dedifferentiate into a more aggressive lesion. MATERIAL AND METHODS: We reviewed 7 parosteal osteosarcomas treated in La Paz Hospital between 2005 and 2009 (3 were dedifferentiated parosteal osteosarcomas). The authors analysed the clinical and radiological features, histology, treatment and outcomes in this patient group. RESULTS: There were 5 men and 2 women, with a mean age of 32.14 years, range 24-47 years. Three of seven tumours (42.8%) were dedifferentiated osteosarcomas. All three patients received chemotherapy. One patient presented with pulmonary metastases. No patient died. CONCLUSIONS: It is important to understand that the biological phenomenon of dedifferentiation can occur in parosteal osteosarcomas. The prognosis, treatment and survival changes radically.

Local recurrence of a parosteal osteosarcoma 21 years after incomplete resection.

Parosteal osteosarcoma (POS) is the most common form of surface osteosarcoma. Its symptoms are insidious and its duration prior to diagnosis is considerably longer than that of other types of osteosarcoma. We report a case of POS with a growing mass but no evidence of metastasis. This tumor, which was diagnosed as calcified hematoma with benign characteristics, was incompletely resected in our hospital 21 years before the diagnosis of recurrence. The patient underwent a wide en bloc resection in our hospital and was free of symptoms, with no signs of tumor recurrence or metastasis during a 53-month follow-up.

Femoral parosteal osteosarcoma 18 years after its discovery: a case report.

Osteosarcomas are a heterogeneous group of tumors with diverse anatomical, clinical, and progressional characteristics. Parosteal osteosarcoma, or juxtacortical osteosarcoma, is a rare form of osteosarcoma that develops at the bone surface, but has a better prognosis than other conventional osteosarcomas. We report the observation of a 22-year-old female patient whose initial presentation was an enormous tumefaction of the knee that had been progressing for 10 years. The biopsy concluded in PO of the lower third of the femur. Staging was negative. The tumor had reached an enormous size and required amputation of the left lower extremity. A custom external prosthesis was manufactured to get her back to walking. Eight years after surgery, no local recurrence or metastasis has been detected. Parosteal osteosarcoma is a rare form of osteosarcoma with very slow progression (in spite of the particularly dramatic presentation in our observation), with an excellent prognosis and very rare metastasis.

Parosteal osteosarcoma of the orbit.

A 60-year-old woman was referred to Bristol Eye Hospital because of a progressive, painless, right proptosis. CT revealed a well-defined, hyperdense lesion adjacent to the lateral orbital wall. A marginal excision was performed. The mass was stony-hard, lobulated, and encapsulated. Histopathologic findings were consistent with a low-grade parosteal osteosarcoma. Parosteal osteosarcoma is a rare osteogenic tumor that usually affects the long bones. It represents a malignant, though well differentiated, tumor that has a relatively good prognosis after a wide excision. However, local recurrences are not rare and have been associated with dedifferentiation. The latter affects the prognosis adversely and, thus, regular follow-ups are strongly suggested after the initial tumor excision. In the present case, no further treatment was administered and the patient was reported disease free 26 months after surgery.

Dedifferentiated parosteal osteosarcoma with giant cell tumor component.

Dedifferentiated parosteal osteosarcoma is characterized histologically by the admixture of low-grade fibroblastic osteosarcoma and a high-grade component typically resembling conventional osteosarcoma or malignant fibrous histiocytoma. We report an unusual distal femoral dedifferentiated parosteal osteosarcoma in which the dedifferentiated component resembled a giant cell tumor of bone. This phenotype is rarely described in the dedifferentiated component of a dedifferentiated parosteal osteosarcoma. The clinical, radiographic, and pathologic features of this unusual tumor are described to further expand the histologic spectrum of dedifferentiated parosteal osteosarcoma.

Clinical outcome of parosteal osteosarcoma.

BACKGROUND: Parosteal osteosarcoma is a rare type of osteosarcoma with distinct characteristics. Clinical outcome of 21 patients was analyzed to assess the predictive relevance of surgical margin, intramedullary tumor extension and histologic grade. METHODS: There were 5 mens and 16 womens with an average age of 26 years. Average follow-up was 9.1 years (range 2.5-22.1). Most common sites were distal femur (15) and proximal humerus (2). No patient presented with metastasis. Surgical margin was wide in 13 and marginal in 8. Intramedullary extension was seen in 10 patients (48%). Focal high-grade 2 and 3 tumors were seen in 11 (52%) and 3 (14%) patients respectively. RESULTS: Twenty patients (95%) were alive without disease. Two (10%) had relapse, one with local recurrence and another with local recurrence and lung metastasis. Of eight marginal procedures performed, 2 turned out to have histologically tumor-positive margins, both of whom later developed relapses. All patients with histologically negative margins remained disease-free. Presence of intramedullary extension and focal high-grade tumor was not significantly associated with relapse. CONCLUSIONS: A marginal but histologically negative margin of excision appears adequate for parosteal osteosarcoma. However, long-term follow-up is warranted for monitoring of rare incidences of local recurrences or distant metastases.

Parosteal osteosarcoma: case report and review of the literature.

BACKGROUND: The majority of osteosarcoma cases of the head and neck are high-grade lesions. We present a case and discuss the diagnostic and therapeutic implications of a rare low-grade parosteal osteosarcoma of the maxilla. METHODS: A 32-year-old man presenting to the Head and Neck Surgical Oncology clinic with a 1-year history of a firm palatal mass. Evaluation clinically and radiographically raised the suspicion of an osteosarcoma. RESULTS: A partial maxillectomy revealed a parosteal osteosarcoma with negative margins. No adjuvant therapy was recommended, and the patient remains without evidence of local recurrence after 3 years. CONCLUSIONS: Parosteal osteosarcomas of the head and neck region are rare, low-grade variants of osteosarcoma, but have the potential to recur with simple local excision. Clinical and radiographic features are diagnostically helpful. Definitive diagnosis comes from histopathology, and wide local resection should be employed as the optimal treatment.