Abdominal Metastasis of a Parosteal Osteosarcoma of the Femur: an Unusual Cause of Large-Bowel Obstruction

Background: Parosteal osteosarcoma is a rare, well-differentiated, predominantly fibro-osseous variant of osteosarcoma. It is regarded as a distinct form of osteosarcoma with better prognosis than conventional osteosarcoma. Aim: We report an unusual case of abdominal mass recurrence of parosteal osteosarcoma of the left distal femur treated eight years previously with wide resection, hip disarticulation and chemotherapy, which presented as an acute abdomen: we discuss the clinical outcomes of this rare entity.

Case presentation: We present a 54-year-old patient with low-grade parosteal osteosarcoma of the left distal femur. Left total hip disarticulation was indicated after several local relapses of the tumour following extensive resection and chemotherapy. Eight years later, he presented with an acute large bowel obstruction secondary to a compression of the large bowel by an abdominal mass. Abdominal computed tomography showed a large abdominal calcified mass with dilated large bowel loops. During laparotomy, the mass was unresectable. So, the patient underwent emergent colostomy of diversion. Biopsy of the lesion yielded grade III parosteal osteosarcoma material. The patient received adjuvant chemotherapy, but the response was poor: six months later, the patient presented with a peristomal mass and two pulmonary metastases.

Conclusion: Abdominal recurrence of parosteal osteosarcoma of the distal femur eight years after definitive surgery is rare. This case emphasises the importance of the long-term follow-up of patients with parosteal osteosarcoma.     

Bizarre parosteal osteochondromatous proliferation of a phalanx

Summary A rare proliferative osteochondromatous malformation of a proximal phalanx is described. This malformation may mimic the appearance of a sessile osteochondroma or parosteal osteosarcoma on X-rays and may be mistaken for a low-grade osteosarcoma on histology, with disastrous therapeutic consequences. We found that cryotherapy followed by local excision was adequate to remove the tumour.     

Pathomorphology of parosteal osteosarcoma. Experience with 125 cases in the Hamburg Register of Bone Tumors

Parosteal osteosarcoma is a rare low-grade bone tumor. It occurs between the 2nd and 8th decade of life. In our own series of 125 parosteal osteosarcomas, most patients were aged between 30 and 40.The most frequent location was the distal dorsal femur.Until clearly proven otherwise, a bone-forming tumor in this location has to be regarded as a parosteal osteosarcoma.Of all parosteal osteosarcomas 77% are located in the lower extremity, with a female sex predominance in this location (62%); 18% are located in the upper extremity; 15% of all parosteal osteosarcomas are located in the humerus. Just 6% of all parosteal osteosarcomas are observed in the skull, the spine, and the pelvis. The tumor is characterized by hyalinized fibrous stroma with a low cell content without substantial nucleus polymorphism and variably dense bony trabeculae.The diagnosis can be difficult due to highly differentiated areas with fat tissue within the marrow and very uniformly bony structure. The operation material has to be analyzed very carefully, because the extent of dedifferentiated areas and most probably also the extent of invasion of the medullary cavity determine the prognosis and occurrence of recurrencies.The tumor is most commonly misinterpreted as osteochondroma or heterotopic ossification. Paying attention to all radiologic and histologic criteria,osteoblastic eccentrically located high-grade osteosarcomas can be clearly distinguished from parosteal osteosarcoma. An intramedullary located low-grade osteosarcoma,which is differentiated like a parosteal osteosarcoma,is histologically indistinguishable from the parosteal variant.This variant requires the synthesis of all available data to find the correct diagnosis.The parosteal osteosarcoma shows like no other tumor the necessity of close cooperation of all involved disciplines for diagnosis and therapy.     

Parosteal osteosarcoma of the ulna: a rare low-grade malignant neoplasm. Case report and review of the literature

Parosteal osteosarcoma is a rare low-grade malignant neoplasm. A case localized at the distal ulna is reported, and the tumour's radiological and histological features are described. Wide enbloc resection without postoperative adjuvant chemotherapy was the treatment. Good clinical function without signs of local recurrence was observed at the 3-year follow-up.     

Parosteal osteosarcoma of the posterior aspect of the distal part of the femur. Oncological and functional results following a new resection technique

BACKGROUND: Parosteal osteosarcoma is a low-grade malignant bone tumor that arises from the surface of the metaphysis of long bones. Parosteal osteosarcoma is usually well differentiated and displays a low propensity to metastasize. Wide resection of a parosteal osteosarcoma has been shown to provide a relatively risk-free method of preventing local recurrence. We propose a new method of resection of parosteal osteosarcomas located in the popliteal paraosseous space of the distal part of the femur. This method involves resection of the mass through separate medial and lateral incisions, which allows for wide margins yet limits the amount of dissection of the soft tissues and the neurovascular bundle. METHODS: Six patients with parosteal osteosarcoma located on the posterior aspect of the distal part of the femur underwent resection of the lesion and reconstruction with a posterior hemicortical allograft through dual medial and lateral incisions. The patients were evaluated with regard to pain, postoperative function, union of the allograft (osteosynthesis), and the prevalence of local recurrence. RESULTS: The average time until the last follow-up assessment was 4.3 years. No metastases developed, and there were no local recurrences. All patients were free of disease at the last follow-up evaluation. Postoperatively, the average range of motion of the knee was 0 to 122 degrees. Five of the six patients were free of pain at the time of the latest follow-up. Five of the six patients returned to their preoperative active functional status. CONCLUSIONS: We recommend resection of a parosteal osteosarcoma located on the posterior surface of the femur through separate medial and lateral incisions. This approach provides minimal dissection of the neurovascular bundle but ample exposure for reconstruction with a hemicortical allograft.     

Parosteal osteosarcoma of the distal ulna. A rare tumour at a rare location: a case report

We report a case of a histologically well differentiated, grade I, parosteal osteosarcoma of the distal ulna. The tumour's radiological and histological features are described, and the patient's course after wide en-bloc resection is detailed. Parosteal osteosarcoma is a rare low-grade malignant neoplasm. It belongs to the group of the osteosarcomas originating from the surface of the bone, representing a distinct tumour entity within this group, with defined histological and radiological features. We describe the radiological and histological characteristics of parosteal osteosarcoma and, based upon these features, present its classification. The differential diagnosis, including parosteal osteoma, myositis ossificans and osteochondroma, is also discussed. Finally, therapy and prognosis are outlined in accordance with the current literature. Wide en-bloc resection represents the mainstay of therapy offering an excellent prognosis with a 5-year survival rate of more than 90%. Incomplete resection, on the other hand, increases the risk of recurrence and dedifferentiation of the tumour. Dedifferentiation induces tumour spread and is associated with a poor prognosis equivalent to conventional osteosarcoma.     

367例原发性骨肉瘤流行病学及临床病理分析

目的 分析原发性骨肉瘤的流行病学和临床病理特征.方法 回顾性分析我院收治的367例原发性骨肉瘤患者的临床资料,对年龄、性别、肿瘤部位、外科分期等临床特征和病理类型、病理分级等病理特征进行分析.结果 原发性骨肉瘤好发于11～30岁者,多见于股骨（42%）,胫骨（28%）,腓骨（9%）,肱骨（10%）.其中约88%的患者病理分级较高,普通型骨肉瘤是最常见的病理类型（82.83%）,11.44%出现早期转移.病理分级较低者多为骨旁型（7.08%）、低级别中央型（3.81%）和骨膜型（1.09%）.结论 对原发性骨肉瘤流行病学和临床病理分布的认识有助于早期诊断和治疗.     

Low-grade central osteosarcoma mimicking fibrous dysplasia: a report of two cases

Low-grade central osteosarcoma is an unusual variant of conventional osteosarcoma. We present here two rare cases of low-grade central osteosarcoma resembling fibrous dysplasia. A 24-year-old woman diagnosed as fibrous dysplasia was treated with intra-lesional excision and curettage of the tumor but tumor recurred at 4 months after surgery. Distal femoral en-bloc resection was performed followed by arthroplasty with mega-prosthesis of the knee. A 57-year-old man diagnosed as central osteosarcoma was treated with wide excision of the tumor, followed by reconstruction with the vascularized fibula graft combined with an autogenous irradiated bone graft. Because of the difficulty in distinguishing low-grade central osteosarcoma from a benign lesion, open biopsy is needed to obtain a large tumor sample. Careful clinical and pathological evaluation is required to obtain a definite diagnosis. The treatment of low-grade central osteosarcoma is en-block resection with wide surgical margins.     

Dedifferentiated parosteal osteosarcoma

Parosteal osteosarcoma is an uncommon malignant tumor of bone, and in a review of Mayo Clinic records we identified eleven cases of so-called dedifferentiated parosteal osteosarcoma. Ten of the eleven patients had had a long history of treatment for multiple recurrences of the tumor as a low-grade parosteal osteosarcoma and then for a definite recurrence as a high-grade undifferentiated osteosarcoma. The prognosis in this group of patients was similar to that in patients with conventional osteosarcoma.     

Surface osteosarcomas: Diagnosis,treatment and outcome

Surface osteosarcomas are a rare form of osteosarcomas accounting for around 3-6% of all osteosarcomas. Three major groups of surface osteosarcomas are parosteal, periosteal and the high grade surface osteosarcomas. Of these, the parosteal osteosarcoma is the most common. Parosteal and periosteal osteosarcomas are distinct clinical entities and it is important to identify the clinicoradiological differences between the two types. Surface osteosarcomas occur at a later age as compared to conventional osteosarcomas. The classical site is the lower end of the femur followed by the upper end of the tibia and upper end of humerus, in that order. The periosteal variant affects the tibia more commonly than the parosteal variety. Neo-adjuvant chemotherapy is the standard of care for high grade surface osteosarcomas. Parosteal osteosarcomas, being low grade lesions, can be treated by upfront wide excision without adjuvant systemic therapy. Controversy prevails over the need for chemotherapy in periosteal osteosarcomas, which are intermediate grade lesions.     

Limb salvage procedures for children with osteosarcoma: an alternative to amputation

Amputation remains the standard surgical management for patients with osteosarcoma. However, in carefully selected patients, eradication of the primary tumor can be achieved by En-Bloc resection of the affected bone preserving both anatomical and functional status. Our criteria for limb salvage procedures are that patients must: (1) be age 12 years or older, (2) have no angiographic or clinical evidence of neurovascular involvement, (3) have low-grade osteosarcoma and/or good response to preoperative chemotherapy, and (4) be compliant. Between November 1980 and October 1982, 32 patients with osteosarcoma of an extremity were seen. Eight patients ranging in age from 13 to 21 years underwent limb salvage procedures. Five of these had Tikhoff-Linberg procedures for upper extremity lesions, two had En-Bloc resections for distal femur lesions, and one patient had a segmental arthrodesis for a distal tibial lesion. Of these eight patients, two had low-grade parosteal osteosarcoma. Follow-up ranged from 10 to 28 months (median 16 months). The two patients with parosteal osteosarcoma received no further therapy, while the other six patients received multiple agent chemotherapy. One patient died at 18 months with bilateral pulmonary disease. None have had local recurrences. Two of the eight patients had minor skin necrosis, requiring revision subsequently. Three patients have had transient nerve palsy. All have had good functional results. With careful selection of patients by rigid criteria, limb salvage procedures can be a viable alternative to amputation.     

Osteosarcoma: A Multifactorial Clinical and Histopathological Study with Special Regard to Therapy and Survival

A multifactorial analysis was performed on all 153 unequivocal cases of genuine osteosarcoma recorded in the Swedish Cancer Registry for the years 1958 through 1968. Cases of so-called parosteal osteosarcoma, soft-tissue osteosarcoma and osteosarcoma secondary to Paget's disease of bone were not included. The osteosarcomas were subclassifiecl as follows: osteoblastic (69 per cent), chondroblastic (19 per cent) and fibroblastic (12 per cent). The overall 5-year survival rate was 22 per cent; 55 per cent for those who had undergone amputation above the joint proximal to the involved skeletal part, 22 per cent for those amputated on the involved skeletal part, 11 per cent for those treated with local extirpation of the tumor, and 1 per cent in cases in which the lesion was not radically removed. Tumors of the femur, humerus and scapula were as malignant as axial tumors. The former carried a 5-year survival rate of 13 per cent, regardless of whether the patients had been treated with exarticulation or amputation on the involved skeletal part. Patients with axial tumors showed a 5-year survival rate of 15 per cent. These survival data suggest that proximal amputation alone might suffice for lesions situated distally to the knee and elbow joints, while tumors in the humerus and femur should be treated with amputation combined with multicytostatic treatment or immunotherapy and axial tumors with local resection and multicytostatic or immunologic treatment.     

Parosteal osteosarcoma of the tarsus

Parosteal osteosarcoma is a very rare bone tumor with a predilection for the posterior aspect of the distal femoral metaphysis. A case of parosteal osteosarcoma of the tarsus of a 23-year-old woman is reported. This is the second case of parosteal osteosarcoma of the tarsus reported in the English literature.     

Juxtacortical osteoma of the ulna

 A case of juxtacortical osteoma of the ulna in a 47-year-old woman is presented. She had a dense bony mass on the ulna. Radiological examinations (plain radiography, computed tomography, magnetic resonance imaging) strongly suggested a rare case of juxtacortical osteoma of a long tubular bone. The differential diagnosis included parosteal osteosarcoma, melorheostosis, osteochondroma, end-stage juxtacortical myositis ossificans, and fibrous dysplasia protuberans. The tumor was excised totally for thorough pathological examination, which revealed it to be composed of lamellar bone, suggesting that the origin was periosteal. Received: May 7, 2002 / Accepted: July 8, 2002 Offprint requests to: T. Goto     

Parosteal osteosarcoma (POS). Clinical and therapeutic aspects

Parosteal osteosarcoma is a malignant bone-forming tumor, which is characterized by its superficial origin and its high structural differentiation. Because of the radiological and histological variability, finding the right diagnosis is a great challenge for physicians, radiologists, and pathologists, especially at the time of primary manifestation. Usually there is a low-grade malignancy. Often a benign tumor is imitated so that finding the correct diagnosis is indispensable.Wide resection with sufficient margin is the adequate therapy. High-grade parosteal osteosarcoma needs adjuvant chemotherapy. Our own experience with secondary dedifferentiation and the possibility of primary undergrading shows that regarding diagnostics, operative therapy, and follow-up parosteal osteosarcoma should be treated like conventional osteosarcoma.     

MDM2 and CDK4 immunohistochemical coexpression in high-grade osteosarcoma: correlation with a dedifferentiated subtype

Low-grade osteosarcomas comprise a distinct subset of osteosarcomas. They may occasionally dedifferentiate into high-grade tumors, typically in the form of high-grade osteosarcoma, which are histologically indistinguishable from conventional osteosarcomas. MDM2 and CDK4 are often amplified in low-grade osteosarcomas and their dedifferentiated counterparts, and the encoded proteins are accordingly overexpressed. As MDM2/CDK4 expression was reportedly rare in conventional osteosarcoma, we hypothesized that these markers may help separate dedifferentiated osteosarcoma from the conventional type. To test this, we performed MDM2 and CDK4 immunohistochemistry on 81 primary and 26 recurrent/metastatic high-grade osteosarcomas and correlated these data with the histology of the primary resection material, with particular attention to the potential presence of any coexisting low-grade osteosarcomatous components. MDM2 and CDK4 coexpression was identified in 7 cases, and on careful histologic review 6 of them were discovered to contain foci of coexisting low-grade elements. One case was a known dedifferentiated parosteal osteosarcoma, and the remaining 5 cases were newly identified dedifferentiated osteosarcomas in which the limited low-grade components were originally unrecognized. An additional 11 cases expressed either marker alone, whereas the remaining 89 cases were negative for both markers; no resection material from these 100 cases presented with a low-grade component. MDM2/CDK4 gene amplification status, determined by quantitative polymerase chain reaction in selected cases, was largely concordant with immunoexpression. Our data suggest that MDM2 and CDK4 coexpression in high-grade osteosarcomas is sensitive and specific to those that progressed from low-grade osteosarcomas, and immunohistochemistry may help identify this dedifferentiated subgroup to facilitate accurate subclassification.     

Bizarre Parosteal Osteochondromatous Proliferation (Nora’s Lesion) of the Mandible. A Rare Bony Lesion

Bizarre parosteal osteochondromatous proliferation (BPOP) also eponymically called “Nora’s lesion”, is a rare benign reactive bone lesion first reported in 1983. BPOP occurs classically on the bones of the hands and feet and long bones. This lesion can easily be confused, both clinically and microscopically, with other benign and malignant lesions of bone, including osteochondroma, parosteal osteosarcoma, myositis ossificans and reactive periostitis. BPOP has been reported to have a high rate of recurrence. Only 3 cases of BPOP of the head and neck have been reported in the literature, of which one involved the maxilla. We present a rare case of BPOP involving the mandible in a 10 year old African American male. Microscopically, a fibro-cartilaginous cap giving rise to a proliferation of variably mineralized osteophytic finger-like projections of bone was seen. Multiple trabeculae of “blue bone” were noted as well as numerous atypical appearing chondrocytes. The lesion recurred within 4 months following the initial excision but has not recurred to date after the second local excision. To the best of our knowledge, this is the first report of BPOP arising in the mandible. In addition, we discuss the clinical and microscopic features, differential diagnosis, and prognosis of this rare entity. We present a case of BPOP of the mandible and believe this is the first report of such a case in the mandible.     

A Case Report of Heel Pain Mimicking Plantar Fasciitis and Osteosarcoma: A Unique Presentation of a Nora's Lesion

Bizarre parosteal osteochondromatous proliferation, otherwise known as “Nora's lesion,” is a rare benign neoplasm first described by Nora in 1983. The exact etiology of this neoplasm remains unknown, and its presentation in the lower extremity presents a diagnostic challenge, as both clinical and radiologic features cannot fully differentiate it from other neoplasms. We present the case of a 48-year-old female with plantar heel pain secondary to Nora's lesion mimicking plantar fasciitis and periosteal osteosarcoma. Following bone biopsy for histopathologic analysis, the patient's symptoms spontaneously resolved, and she returned to activity with complete resolution of symptoms 18 months post biopsy. Bizarre parosteal osteochondromatous proliferation as an etiology for plantar heel pain has not been previously described in the literature. Although rare, it should be considered in the differential diagnosis for patients presenting with plantar heel pain, especially after failed conservative treatment. Following diagnostic confirmation by histopathology, complete surgical excision is the treatment of choice.     

The role of imaging modalities in the diagnosis of primary dedifferentiated parosteal osteosarcoma

Dedifferentiated parosteal osteosarcoma (dd-POS) is defined as high-grade sarcomatous components coexisting with low-grade POS components. With regard to the histological diagnosis of dd-POS, the sampling of a small area of dedifferentiation through the densely mineralized POS can be a problem. In this situation, imaging is important to identify the area with the highest possibility of dedifferentiation. We report a patient in whom dedifferentiation was shown by computed tomography (CT) and magnetic resonance imaging (MRI). CT revealed a radiolucency in a highly mineralized area. T2-Weighted MRI showed a relatively high signal intensity, corresponding to the radiolucency, surrounded by a very low signal intensity area. Furthermore, gadolinium-enhanced T1-weighted MRI showed marked enhancement. Based on these imaging techniques, the condition was diagnosed as most likely to be a dd-POS, although a representative sample was not accessible by incisional biopsy. Neoadjuvant chemotherapy was administered, followed by wide resection and adjuvant chemotherapy. Four years after the surgery, partial lobulectomy was required because of a pulmonary metastasis. Three years after the second surgery, the patient remained well without evidence of metastases. Based on the initial diagnosis and, consequently, the optimal treatment of combined chemotherapy and wide resection, our patient showed a good clinical outcome. Received: November 22, 2000 / Accepted: January 12, 2001