Bizarre parosteal osteochondromatous proliferation (Nora's lesion): a retrospective study of 12 cases, 2 arising in long bones

Multifocal Bizarre Parosteal Osteocartilaginous Proliferation of the Foot: A Case Report

CASE

Bizarre parosteal osteocartilaginous proliferation (BPOP) is rare, especially in the foot. To the best of our knowledge, multifocal BPOP has yet to be reported. We are reporting a case of a 40-year-old woman who presented with 4 bumps over her midfoot and toes. After staging studies, we excised the lesions, and histopathology confirmed BPOP. No local recurrence was observed at the end of the 2-year follow-up.

CONCLUSION

BPOP should be considered in the differential diagnosis of multiple foot bumps, whether synchronous or metachronous, which may present multifocally in the foot.

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: 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.

Unusual Site of a Bizarre Parosteal Osteochondromatous Proliferation (Nora's Lesion) Involving the Scapula: First Case Report and Review of the Literature

Bizarre parosteal osteochondromatous proliferation (BPOP), also known as Nora's lesion, is a rare benign surface lesion of bone that typically occurs in the hands and feet. We report herein the first case of BPOP occurring in an unusual location, specifically the scapula of a 29-year-old male patient. The lesion exhibited features mimicking those of a peripheral chondrosarcoma because of its atypical location in the axial skeleton and the presence of calcification, which indicates the presence of cartilaginous matrix. Treatment involved a wide surgical resection, and histopathological examination confirmed the diagnosis of BPOP of the bone. At a five-year follow-up, there was no evidence of local recurrence.

Bizarre Parosteal Osteochondromatous Proliferation (Nora Lesion): A Narrative Review

Background

Bizarre parosteal osteochondromatous proliferation (BPOP), or Nora lesion, is a rare proliferative disease arising from the parosteal region of bones. Although BPOP's pathogenesis is still not certain, modern literature suggests it to be a tumor-like lesion or even a benign neoplasm. Due to the extremely low incidence, to this date studies on the topic are limited to case reports and a few case series. This narrative review aims to resume literature on BPOP and provide an overview of its natural history, morphologic characteristics and prognostic horizon.

Materials and methods

A systematic research of the literature was done to identify studies reporting on patients who suffered from BPOP between 1983 and 2021. We collected data regarding aetiologic and pathogenetic theories, patients' personal data and anamnesis, lesions' location, clinical presentation, imaging features, pathological appearance, treatment and prognosis.

Results

We identified 322 cases of BPOP with a mean age of 34.3 years at the moment of diagnosis. There was no gender difference. The most involved site was the hand, followed by the foot. A history of trauma was reported for 14.7% of the cases. 38.7% of the patients had pain. Literature defined typical radiographic and microscopic patterns that characterize Nora lesions. While imaging is fundamental to orientate towards BPOP, histological evaluation is mandatory to get the definitive diagnosis. To this date, only reliable therapeutic option is represented by surgical resection. BPOP is burdened by a risk of recurrence that accounts to 37.4%.

Conclusion

BPOP is a rare benign disease that should be considered during the differential diagnosis of parosteal lesions, especially in the acral regions. Careful diagnostic evaluations are necessary to get the correct diagnosis and wide margins of resection are recommended to minimize the relatively high risk of local recurrence.

Bizarre Parosteal Osteochondromatous Proliferation (Nora Lesion) in Pediatric Phalanges

Bizarre parosteal osteochondromatous proliferation, or Nora tumor, is an uncommon lesion affecting the tubular bones of the hands and feet. Normally arising from the cortical surface and periosteum of these bones, these lesions histologically consist of a hypercellular cartilaginous cap covering a bony stalk that is surrounded by ossified areas and spindle cell stroma. The differential diagnosis includes conditions involving the periosteum such as chondrosarcoma, parosteal osteosarcoma, osteochondroma, turret exostosis, and florid reactive periostitis. The only effective treatment is wide surgical excision; nevertheless, local recurrence rates are extremely high and may necessitate revision surgery. In the present study, we report 3 cases of Nora lesion located in the hand in pediatric patients. The diagnosis in these cases was challenging owing to their presenting symptoms and radiographic findings. The diagnosis was made based on characteristic findings noted on the radiographic images and was confirmed by histological examination following excision.

Bizarre Parosteal Osteochondromatous Proliferation (Nora Lesion) in Upper and Lower Limbs: A Report of Three Cases and Review of Literature

Introduction:

Bizarre parosteal osteochondromatous proliferation (BPOP) is a rare bone pathology affecting small bones of hand and feet. This benign lesion needs to be distinguished from many malignant bone tumors as it poses a diagnostic dilemma due to its clinical, radiological, and histological picture. We report three cases of BPOP affecting the hand and foot.

Case 1:

A 21-year-old gentleman presented with painful swelling in the long finger of the right hand. A plain radiograph showed a radio dense mass which was later excised and diagnosis confirmed in histopathology. There was no recurrence in 2 years of follow-up.

Case 2:

A 5-year-old boy presented with painful swelling over the right ankle with no history of antecedent trauma. Following radiological evaluation, the patient was successfully treated with excision.

Case 3:

A 35-year-old lady presented with a painful swelling on the dorsal aspect of her hand which was gradually increasing in size. After radiological evaluation, the patient was successfully treated with excision and lesion confirmed to be BPOP on histological examination. She was symptom free without recurrence in up to 2 years of follow-up.

Conclusion:

Nora’s lesion is a rare pathology requiring high index of suspicion. Excision is the recommended mode of treatment. All our cases responded well with excision with immediate pain relief following surgery and no recurrence in up to 2 years of follow-up.

Bizarre Parosteal Osteochondromatous Proliferation (Nora's Lesion) in the Medial Sesamoid of the First Toe

Bizarre parosteal osteochondromatous proliferation, or Nora's lesion, is a unique bony lesion that generally originates from the small bones of the hands and feet in young adults. We report a case of a bizarre parosteal osteochondromatous proliferation originating from the medial sesamoid of the first toe that was managed surgically by en bloc excision. At 5-year follow-up, there was no evidence of recurrence.

Bizarre Parosteal Osteochondromatous Proliferation (Nora's Lesion) of Mandible With Recurrence: Case Report and Review of Literature

Bizarre parosteal osteochondromatous proliferation (BPOP) is a rare benign lesion exhibiting radiographic and histologic features that can be mistaken for malignancy. Most cases have been reported in the small tubular bones of the hands and feet, but involvement of the skull and jaws is extremely rare. Here, we present a case of BPOP involving the mandible in a 23-year-old male that, after initial excision, recurred within 18 months. To the best of our knowledge, this is only the third published case of BPOP arising in the mandible.

Nora's Lesion: Bizarre Parosteal Osteochondromatous Proliferation Causing Splay Foot Deformity: A Case Report

Nora's lesion, or bizarre parosteal osteochondromatous proliferation (BPOP), is a rare benign lesion that is made up of varying degrees of cartilage, bone, and spindle cells. Most notably, calcification of the cartilage or "blue bone," is a feature of the disorder. The condition principally affects long tubular bones of the hands and feet, and is generally seen in patients in their second and third decades of life. We present a case of BPOP occurring in the second interspace with symptoms that would be consistent with a more common diagnosis of predislocation syndrome, or a second interspace neuroma. This case study may help the clinician in considering a more subtle cause of a splay deformity in the second interspace, and walk through the diagnostic and treatment course for BPOP.

Bizarre Parosteal Osteochondromatous Proliferation- A Case Series of Typical and Atypical Presentations

INTRODUCTION

Bizarre parosteal osteochondromatous proliferationis a distinct entity which requires proper radiological and pathological distinction for correct surgical management.

CASE REPORT

We present a series of four cases which were misdiagnosed by the treating surgeons, reporting radiologists and pathologists due to clinical and investigatory consistencies with other benign or malignant orthopedic tumors. Due to common diagnostic errors of these uncommon tumors, the patients had recurrence and required multiple invasive procedures which could have been avoided with high index of suspicion.

CONCLUSION

Dueto high local recurrence rates and a lack of adjuvant therapy options, this lesion will continue to pose a challenge for orthopedic surgeons and more awareness ofthis lesion will help identify and understand that a wide excision, with no compromise related to the margins, is required for this benign-appearing lesion.

Bizarre parosteal osteochondromatous proliferation of the femur: A case report

A 54-year-old man initially presented with left distal thigh pain during walking. Imaging analysis revealed a diffuse calcified or ossified mass adjacent to the medial cortex of the distal femur and absence of continuity with the medulla. We performed resection biopsy. Histological examination revealed a large amount of hypercellular cartilage showing transformation to trabecular bone and BPOP was diagnosed. Postoperative course was uneventful and he remained free of recurrence. The method of resection should depend on the stage of reactive proliferation and whether the lesion is pathologically immature or mature. We also provide a brief review of the literature.

Bizarre parosteal osteochondromatous proliferation: 16 Cases with a focus on histologic variability

Bizarre parosteal osteochondromatous proliferation (BPOP) is a benign bone and cartilage forming tumor occurring on the surface of bones, predominantly on the hands and feet. A defining feature of BPOP is the purplish-blue mineralization of cartilaginous tissue, known as 'blue bone.' Here, we report on an institutional series of 16 cases of BPOP, including radiographic, histologic, and histomorphometric features. All tumors were composed of some element of bone, cartilage, fibrous tissue and 'blue bone,' though the amount of each tissue sub-type varied widely. Some cases showed focal 'blue bone' only, however this was a defining feature in all cases.

Differences in molecular regulation between osteochondroma and bizarre parosteal osteochondromatous proliferation

The differences in molecular mechanisms between osteochondroma and bizarre parosteal osteochondromatous proliferation (BPOP) remain to be fully elucidated. In the present study, the differentially expressed genes between BPOP and osteochondroma were obtained from the Gene Expression Omnibus online database, and the associations among these genes were analyzed using the Database for Annotation, Visualization, and Integrated Discovery (DAVID) online bioinformatics software. The results revealed several differentially expressed genes between human BPOP and osteochondroma. These differentially expressed genes were also enriched in different subgroups based on the analysis using DAVID online software, including ‘transforming growth factor β receptor signaling pathway’, ‘BMP signaling pathway’, ‘Wnt receptor signaling pathway’, ‘response to chemical stimulus’, ‘regulation of inflammatory response’, ‘response to stress’, ‘glycosaminoglycan binding’, ‘polysaccharide binding’, ‘extracellular matrix structural constituent’ and ‘growth factors binding’. Taken together, these findings led to the conclusion that different gene regulatory mechanisms exist between BPOP and osteochondroma. Environmental stimulation and inflammation may contribute to BPOP or osteochondroma, and differences in extracellular matrix may contribute to differences in biological characteristics between BPOP and osteochondroma.

Florid reactive periostitis in the fifth phalange of a professional boxer: A case report

RATIONALE

Florid reactive periostitis is a rare, benign bone and chondrogenic lesion that develops most frequently in the phalanges of the hands. Although the definitive cause of florid reactive periostitis is unknown, the major inciting factor is generally considered to be trauma, including repetitive minor trauma.

PATIENT CONCERNS

We present a case of florid reactive periostitis affecting two contiguous phalangeal bones of the left fifth phalange of a 23-year-old male professional boxer. The patient had experienced chronic pain around the metacarpophalangeal joint of the left fifth phalange when punching with the left hand; this pain was improved but not resolved after conservative treatment.

INTERVENTIONS

Plain radiography of the fifth phalange revealed a bulging bone lesion on the volar side of the proximal phalanx and metacarpal of the left fifth phalange. Computed tomography also showed raised bony lesions on the volar side of these bones without bony destruction or intraregional calcification. Surgery was performed and histopathology revealed that the bone specimens comprised a mixture of fibrous connective tissue and relatively immature bone covered by bland osteoblasts.

DIAGNOSES

These findings were suggestive of a benign bone formation process, and the lesion was diagnosed as florid reactive periostitis.

OUTCOMES

The pain and tenderness in the left fifth phalange experienced during boxing had completely resolved by 6 months postoperatively, and 12 years postoperatively the patient had full range of motion and no recurrence of pain.

LESSONS

Traction force, such as those associated with "leading jabs," may induce repetitive minor trauma and subsequent periosteal damage, resulting in the gradual development of bulging bone ridges on the volar surface of the proximal fifth phalange and metacarpus of the hand.

Rare Mimickers of Exostosis: A Case Series

Exophytic growths from bones are a common entity. Osteochondroma is the most common benign exophytic lesion and we tend to diagnose every benign looking exophytic lesion as osteochondroma. Here we reported two entities of cases, one was Nora's lesion and another one was supracondylar process of humerus, both of which were mimickers of osteochondroma and their salient and differentiating features from osteochondromas.

[Bizarre parosteal osteochondromatous proliferation of the metatarsal bone]

A bizarre parosteal osteochondromatous proliferation (BPOP), also known as a Nora lesion, is a rare benign bone formation. It emanates mainly from the intact cortex of the metaphysis of short tubular bones (hands or feet). Conventional radiographs should be complemented using cross-sectional imaging modalities (CT/MRI). In the absence of symptoms a non-operative regime with radiological and clinical controls is possible. If symptomatic, excision biopsy is the treatment of choice, though a high recurrence rate has been reported. Histopathological examination confirms the diagnosis and typically shows an endochondral ossification zone and an unusually mineralized cartilaginous matrix referred to as "blue bone".

Bizarre parosteal osteochondromatous proliferation in the lingual area of the mandibular body versus osteochondroma at the mandibular condyle

Background

Bizarre parosteal osteochondromatous proliferation (BPOP) is benign and usually occurs in the small tubular bones of the hands and feet, but it is extremely rare in the oral and maxillofacial region.

Methods

The present study compares a case of BPOP occurring in the lingual area of the right mandibular body with a representative case of osteochondroma occurring in the left mandibular condyle using immunohistochemical methods.

Results

BPOP showed no continuity to the cortical bone of the mandible on X-ray and was histologically composed of immature cartilage and bone tissues, whereas osteochondroma showed overgrowth of hypertrophic chondrocytes accompanied by mature bone with endochondral ossification. Although BPOP showed no features of cellular atypia or malignant transformation, it expressed more osteogenic proteins, including BMP-2, BMP-4, RUNX2, OC, AP, OPG, RANKL, CTGF, and bFGF, than osteochondroma. Furthermore, the perichondral spindle cells and marrow osteoblasts/fibroblasts of BPOP showed stronger immunoreaction of PCNA, p53, β-catenin, BCL2, pAKT, survivin, 14-3-3, CEA, EMA, pan-K, and S-100 than the tumor cells of osteochondroma.

Conclusions

Therefore, it was presumed that similar to embryonal osteochondroid tissue, BPOP might be activated by osteogenic and oncogenic signaling and that this increased signaling may explain the rapid growth and high recurrence of BPOP.

Differential diagnosis of BPOP arising in relation to patella

INTRODUCTION

Solitary exostosis is common at the metaphysis of long bones, and rarely may it develop in the lower pole of the patella. Usually it stops growing after skeletal maturity unless complicated. When the growth continues after skeletal maturity, other rare possibilities need to be considered such as bizarre parosteal osteochondromatous proliferation (BPOP). Though solitary exostosis is common at the metaphysis of long bones, very rarely it also develops in lower pole of the patella. Usually they stop growing after skeletal maturity unless complicated. When it starts after skeletal maturity and continues to grow, other rare possibilities like bizarre parostealosteochondromatousproliferation (BPOP) are to be thought of.

CASE REPORT

21 years male student presented with anterior midline painless progressive swelling over right knee joint of one year duration which was hard, non-tender, fixed to patella but mobile with patella. X ray showed midline heterogeneously radio-opaque swelling attached to inferolateral aspect of the anterior surface of patella. Patellar out line is fully maintained except the narrow site of tumour attachment. After exposing through midline incision, the swelling was found to incorporate the patellar tendon completely and an anterior vertical midline cleavage was found. The mass was deliberately detached along the cleavage and from intact patellar tendon. Almost full range of knee movement is obtained in operation table. Immediate post operative 10° quadriceps lag was corrected with quadriceps setting exercises in two weeks time. Histopathological examination demonstrated thin layer of cartilage cover, irregular lamellar bone in deeper zone and spindle cells between them without cytoplasmic atypia. Plenty of cartilage cells in different stages of maturation are seen without column formation. Marrow elements are absent. Periosteum could not be demonstrated and there was no other evidence of malignancy. Features simulate 'bizarre parosteal osteochondromatous proliferation'. There is no recurrence in five years of follow up.

CONCLUSION

When exostosis like lesions arise from unusual site and at an unusual age group, other rare conditions need to be investigated. Though the final diagnosis of BPOP is obtained after careful histo-pathological examination, the clinico-radiological findings are also relevant. As literature search indicates, this is possibly second incidence where BPOP arised from sesamoid bone and first from patella.

Florid reactive periostitis ossificans of the humerus: Case report and differential diagnosis of periosteal lesions of long bones

A case of florid reactive periostitis ossificans (RPO) arising in a long bone is presented. This is a rare bone proliferation with a pronounced periosteal reaction. Less than 100 cases have been described in the literature with far fewer outside the bones of the hand, feet, fingers, and toes. Although the etiology is unknown, a relationship to preceding trauma is suggested. The imaging and histologic features show an overlap with other bone lesions including bizarre parosteal osteochondromatous proliferation, subungual exostosis, and malignant surface tumors of bone and cartilage which include, periosteal and parosteal osteosarcoma. It is important to recognize the clinical presentation and diagnostic features of RPO as a benign entity so that it is not mistaken for a more aggressive neoplasm. We present a case of a right distal humeral lesion that on histopathological review revealed florid RPO. This diagnosis was not suspected on imaging studies, but was made on open biopsy of the mass. The patient remains disease free, years postoperatively. In addition to presenting this unique case report, we review the pertinent literature, and offer a differential diagnosis and treatment strategy for its management.

Osteochondroma of the Hyoid Bone: A Previously Unrecognized Location and Review of the Literature

Osteochondroma is a benign cartilaginous neoplasm and the most common benign tumor of bone. Osteochondromas occur primarily in the axial skeleton with a predilection for the distal femur, and relatively few cases occur in the head and neck region. The majority of cases of osteochondromas in the head and neck region affect the mandibular condyle, with fewer cases reported in the skull base and the neck. To our knowledge, there is no reported case of osteochondroma of the hyoid bone documented in the English literature. We thus report the first case of a hyoid bone osteochondroma, presenting as an asymptomatic mass in a young woman.

Periosteal chondroma of the distal tibia: Computed tomography and magnetic resonance imaging characteristics and correlation with histological findings

Periosteal chondroma is a rare benign hyaline cartilage neoplasm situated on the bone surface. This is the presentation of a unique case of periosteal chondroma arising in the left distal tibial metaphysis of a 25-year-old female patient with a history of antecedent trauma. The physical examination revealed swelling and tenderness in the anterolateral aspect of the left distal lower limb. Plain radiographs revealed a discernible soft tissue lesion with peripheral foci of mineralization. Computed tomography scans confirmed the presence of a surface-based mass with peripheral ossification and a thin rim of calcification. On magnetic resonance imaging, the well-circumscribed mass exhibited intermediate signal intensity on T1-weighted sequences and high signal intensity with foci of decreased signal intensity on T2-weighted sequences. Contrast-enhanced T1-weighted sequences revealed predominantly peripheral enhancement without intramedullary involvement. Following an open biopsy, marginal excision with curettage of the underlying bone cortex was performed. Histologically, the tumor consisted of mature hyaline cartilage arranged in distinct lobules. Foci of ossification with mature bone trabeculae forming a thin shell-like structure were identified in the periphery of the tumor. The mindbomb E3 ubiquitin protein ligase 1 labeling index was <1%. Based on these findings, the tumor was diagnosed as periosteal chondroma. There has been no evidence of local recurrence at 4 months following surgery. Despite its rarity, periosteal chondroma must be considered as a possible diagnosis when confronted with a surface-based, mineralized lesion in the metaphysis of long bones.

Bizarre Parosteal Osteochondromatous Proliferation causing angular deformities: A Case Report

Introduction:

There have been fewer than 150 cases of Bizarre Parosteal Osteochondromatous proliferation (Nora Lesions) reported in the literature to date and no significant reports on angular deformities caused by this lesion. Nora’s lesion can easily be misdiagnosed as osteochondroma or chondrosarcoma and therefore inappropriately managed. Although this condition classically appears in the second or third decade, we present to you a three year old boy who presented with multiple bony swellings over the hand and feet that caused an angular deformity of the involved digits. In the case report we have detailed the angular deformities and its treatment outcome.

Case Report:

A three year old boy presented with valgus deformity of middle finger of right upper limb with an associated ulnar bony swelling at the level of middle phalanx which was noticed two years before and was progressing rapidly since last three months. On physical examination the swellings were found to be bony hard, midly tender and found to have been causing an angulare deformity of the digits. The initial suspicion was of osteochondromatous lesion however the excision biopsy showed the lesion to be of the rare entity of bizarre parosteal osteochondromatous proliferation. 1 year follow up showed no progression of angular deformity of the operated digits.

Conclusion:

Bizarre osteochondromatous proliferation is an entity that can rarely present in children which needs to be identified and tackled early to prevent the onset of deformities. Almost all cases warrant surgical intervention and the type of excision varies with the type of lesion.

A bizarre parosteal osteochondromatous proliferation (Nora's lesion) of metatarsus, a histopathological and etiological puzzlement

Nora's lesion (bizarre parosteal osteochondromatous proliferation) is a rare, benign lesion that is composed of differing amounts of cartilage, bone, and spindle cells and an unusual form of calcified cartilage so-called "blue bone". Whether it represents a reactive proliferation or a neoplastic lesion still remains controversial. We present a 24-year-old woman having a 4.5cm two lobulated mass attached to second metatarsus of her left foot. The lesion was hyperintense on magnetic resonance imaging and accompanied by an extensive soft tissue and bone marrow edema. In resection specimen, smaller lobule appeared stuck-on the cortex while the larger one had a broader base and a 0.4cm cartilaginous cap-like formation. The histological picture was best fit to Nora's lesion however showed less fibroblastic tissue and cartilaginous pleomorphism. The lesion also showed areas with cortical invasion and a small focus of fracture callus accompanied by adjacent medullary edema and fat necrosis. The case is presented with the comparative radiologic, macroscopic and microscopic findings for its diagnostic difficulties and etiopathogenetic considerations in favour of a maturation phenomenon in parosteal ostecartilaginous lesions irrespective of the cause.

Recurrent bizarre parosteal osteochondromatous proliferation of the ulna with erosion of the adjacent radius: case report

Bizarre parosteal osteochondromatous proliferation is an unusual entity that should be considered when evaluating a patient with a surface-based bone lesion. The aggressive features of bizarre parosteal osteochondromatous proliferation have occasionally led to misdiagnoses as malignant neoplasms and subsequent aggressive treatment. We present a case of a recurrent forearm bizarre parosteal osteochondromatous proliferation with unique radiographic features. This report serves to illustrate the importance of both radiographic and histopathologic review for correct diagnosis and discusses the successful management of a recurrent forearm lesion.

Florid reactive periostitis of the metacarpal and phalanx: 2 case reports

Florid reactive periostitis is a rare benign fibro-osseous proliferative lesion of soft tissue and is mainly composed of fibrous connective tissue and mature bone. The lesion usually occurs in the finger and seldom in the metacarpal. The lesion mimics malignant and infectious disorders, thus often leading to inappropriate treatment. Radiography usually shows an ossified mass attached to the underlying hand bones without interruption of the cortex. We report 1 case of florid reactive periostitis with unossified mass and underlying bone marrow edema in the metacarpal of hand and 1 case with adjacent cortical destruction in the phalanx. In addition, we describe the imaging findings of computed tomography CT and magnetic resonance imaging MRI and discuss their diagnostic values compared with routine radiographic examination.

Popliteal pseudoaneurysm caused by Nora's lesion of the femur in a young child: a rare presentation and first report

Bizarre parosteal osteochondromatous proliferation (BPOP), or Nora's lesion, was first described by Nora et al. in 1983 as a rare, tumor-like lesion involving the bones of the hands and feet. Popliteal artery pseudoaneursyms in the pediatric population are also unusual. Here, we present a case of a young male with a popliteal artery pseudoaneurysm and distal femur lesion originally thought to be an osteochondroma. A 10-year old, Caucasian male was referred to our facility following an MRI concerning for a popliteal artery pseudoaneurysm. On physical exam, there was a palpable 5 × 5-cm pulsatile mass in the upper popliteal fossa with a normal pulse exam bilaterally. A computed tomographic angiogram demonstrated a 4.5-cm by 1.8-cm by 3.6-cm pseudoaneurysm adherent to a 3.5-cm thick, exostotic lesion of the posterior right femur. He was taken to the operating room for repair of the popliteal pseudoaneurysm and resection of his bone lesion. The final pathology was consistent with a popliteal pseudoaneurysm, osteochondroma, and bizarre parosteal osteochondromatous proliferation (BPOP), otherwise known as Nora's lesion. The location of the lesion and the age of our patient were both atypical for BPOP and to our knowledge, this represents the first report of a resulting popliteal artery pseudoaneurysm.

Primary juxtacortical myoepithelioma/mixed tumor of the bone: a report of 3 cases with clinicopathologic, immunohistochemical, ultrastructural, and molecular characterization

We describe the clinicopathological, immunohistochemical, and molecular features of 3 primary juxtacortical myoepithelioma/mixed tumor of bone. The patients were 2 males (13 and 23 years of age) and a 15-year-old female. The juxtacortical lesions were all located in the femur, and were surgically removed, 2 with wide margins and one with marginal margins. This latter tumor recurred locally 18 months later. The 3 patients were free of disease at 6 to 17 months follow-up. Histologically, all lesions showed a prominent multinodular architecture, and were formed by epithelioid and stellate elements, organized in solid sheets, or embedded in myxoid or chondroid matrix. Areas of osteoid formation were also observed. One tumor had the appearance of classical mixed tumor, showing aspects of duct formation and focal squamous differentiation. Immunohistochemically, all cases were positive for cytokeratins, epithelial membrane antigen, and S100 protein. The expression of other myoepithelial markers, including p63, glial fibrillary acid protein and calponin was more limited. No rearrangement of Ewing sarcoma region 1 (EWSR1) and fused in sarcoma (FUS) genes was observed by fluorescent in situ hybridization. To our knowledge, this is the first report of primary myoepitheliomas of bone arising at juxtacortical sites. These lesions must be distinguished from other benign and malignant bone and cartilage-forming surface tumors, including periosteal chondroma and chondrosarcoma, juxtacortical chondromyxoid fibroma, and periosteal and paraosteal osteosarcoma. The clinicoradiologic presentation and their histological and immunohistochemical features are distinctive enough to allow the separation from these entities.

Nora's lesion: bizarre parosteal osteochondromatous proliferation of the tibia

Bizarre parosteal osteochondromatous proliferation is a rare benign condition of locally aggressive and often recurrent osteochondromatous exostosis arising from the bony cortex. We present a case of a patient who presented with this lesion in her tibia, focusing on imaging findings. Because of the lack of information on the disease's natural history, etiology, and clinical course, a multidisciplinary approach is needed for diagnosis and treatment.

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.

Nora's lesion: Case report and literature review of a bizarre parosteal osteochondromatous proliferation of a small finger

A case of a left small finger tumour that was diagnosed on histopathological review as Nora's lesion (bizarre parosteal osteochondromatous proliferation) is reported. There have been fewer than 150 cases reported in the literature to date and its pathophysiology is yet to be defined. Due to its rare presentation, Nora's lesion can easily go unrecognized and therefore inappropriately managed.

Bizarre parosteal osteochondromatous proliferation: a locally aggressive benign tumor

BACKGROUND

Bizarre parosteal osteochondromatous proliferation (BPOP) is a benign lesion of bone, and numerous questions remain unresolved regarding its etiology, diagnosis, and treatment.

QUESTIONS/PURPOSES

We present the Scottish Bone Tumour Registry experience of this rare lesion.

PATIENTS AND METHODS

We performed a retrospective analysis of the Scottish Bone Tumour Registry records. Histologic specimens were reexamined by a musculoskeletal pathologist. Radiographs were reevaluated by a musculoskeletal radiologist.

RESULTS

From 1983 to 2009, 13 cases (13 patients; six male, seven female) were identified. Their ages ranged from 13 to 65 years. All patients presented with localized swelling. Pain was present in five. Antecedent trauma was present in two. Nine lesions affected the hand, three the foot, and one the tibial tuberosity. Twelve lesions were excised and one was curetted. There were seven recurrences of which six were excised. One lesion recurred a second time and was excised. There were no metastases. Radiographs showed densely mineralized lesions contiguous with an uninvolved cortex. Cortical breakthrough was present in one case and scalloping in another. Histologic analysis characteristically showed hypercellular cartilage with pleomorphism and calcification/ossification without atypia, bone undergoing maturation, and a spindle cell stroma.

CONCLUSIONS

BPOP is a rare benign lesion that probably is neoplastic, with no gender predilection, and affecting patients over a wide age range. Previously trauma was considered an etiologic factor, but this no longer seems to be the case. The rate of recurrence was 50%, which may indicate a more extensive resection is required for this locally aggressive lesion. No metastases were reported. BPOP should not be mistaken for, or treated as, a malignant tumor.

LEVEL OF EVIDENCE

Level IV, retrospective case series. See Guidelines for Authors for a complete description of levels of evidence.

Unusual presentation of bizarre parosteal osteochondromatous lesion of the second toe (Nora's lesion)

Bizarre parosteal osteochondromatous proliferation (BPOP) of bone is a rare benign neoplasm. This report presents the first case of BPOP associated with gangrenous changes and ulceration after remaining symptomless for 20 years. The authors hypothesize that the cause of gangrene may be attributed either to vascular occlusion due to pressure, trauma, or malignant transformation of the lesion. Although local excision of the tumor is the treatment of choice, the authors resorted to ray excision, as gangrenous changes and ulceration were present and there was the possibility of malignant change.

[Nora's lesion. Discussion of a rare bone proliferation]

Nora's lesion, also known as "bizarre parosteal osteochondromatous proliferation" (BPOP), was first described in 1983 by the pathologist Nora. This lesion is defined as a proliferation of the bone. In most cases the lesion emanates from the intact cortical substance of short bones. It used to be assigned to reactive, heterotopic ossifications. More recent publications described constant genetic alterations supposing a tumorous genesis. Nora lesions are mostly found in the third or fourth decade of life; a preference of sexes is not described in the literature. They are characterized by a typical appearance in radiological diagnostics, but the diagnosis is ultimately determined by histopathological examination. Surgical resection is the therapy of choice.We report the case of a 29-year-old patient with an undetermined proliferation of the proximal ulna. The diagnosis of a Nora's lesion was made. The therapeutic approach, differential diagnosis and corresponding literature are presented and discussed.

Tumours of the hand: a review on histology of bone malignancies

Malignant bone tumours of the hands are uncommon. Although almost all lesions that occur in other parts of the skeleton can also affect the hands, their frequency, distribution and clinical characteristics differ. This review focusses on the histology of these tumours and gives an overview of the main differential diagnoses. Close correlation to radiologic and clinical features usually leads to the correct diagnosis.

Bizarre parosteal osteochondromatous proliferation of the metatarsal: a pediatric case report and archival review

Bizarre parosteal osteochondromatous proliferations (BPOP), also known as Nora's lesions, are rare tumors occurring most commonly in the hands and feet. They are benign and rarely exhibit radiological evidence of cortical invasion. We report a case of BPOP showing atypical magnetic resonance imaging features that are inconsistent with BPOP and having a novel chromosomal aberration. We also review the BPOP cases in our regional benign bone tumor database.

LEVEL OF CLINICAL EVIDENCE

4.

[Bizarre parosteal osteochondromatous proliferation or Nora's lesion]

Bizarre parosteal osteochondromatous proliferation (BPOP) is a very rare benign lesion on face bones. The first line treatment is surgical exeresis. The frequency of recurrence after exeresis may suggest a malignancy.

Thoracic myelopathy due to idiopathic epidural ossifications in a child: a case report

STUDY DESIGN

A rare case of thoracic myelopathy due to epidural ossification in a child.

OBJECTIVE

To determine a differential diagnosis of thoracic myelopathy.

SUMMARY OF BACKGROUND DATA

Ectopic ossification is one of the common lesions that can cause thoracic myelopathy. The majority of the cases occur in adults and ossification usually occurs in ligamentous tissues. To the authors' knowledge, no published reports in the English literature have described a case of thoracic myelopathy in a child caused by ectopic epidural and nonligamentous ossification.

METHODS

A 15 year-old girl presented with a chief complaint of bilateral numbness of the thigh and gait disturbance.

RESULTS

Computed tomography demonstrated 3 islands of epidural ossifications that surrounded the dural sac from T2-T4 and compressed the spinal cord. These lesions, which were not due to ossification of the ligament, were surgically resected. After resection, her symptoms completely disappeared. Histologic diagnosis of the removed specimen was fibro-osseous tissue. Radiologic examination demonstrated no recurrence of the lesion 6 years after surgery.

CONCLUSION

We describe this condition as idiopathic epidural ossification, as the reason is unknown and discussed its etiology.

Pseudosarcomas of soft tissue

One of the most common and important pitfalls in soft tissue pathology are the so-called pseudosarcomas. These lesions are nonneoplastic; however, their rapid growth, hypercellularity, cytologic atypia, and mitotic activity makes them prone to be misinterpreted as sarcoma. The most common of these lesions are fibroblastic/myofibroblastic and matrix-forming proliferations, including nodular fasciitis, proliferative fasciitis and myositis, ischemic fasciitis, massive localized edema, myositis ossificans, and bizarre parosteal osteochondromatous proliferation and related entities. Most of these lesions rarely recur following simple excision; therefore, their accurate recognition helps prevent excessive therapy.