Distinct Chromosomal Rearrangements in Subungual (Dupuytren) Exostosis and Bizarre Parosteal Osteochondromatous Proliferation (Nora Lesion)

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

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

Bizarre parosteal osteochondromatous proliferation Nora's lesion: Case report of two cases with review of the literature

ABSTRACT

Bizarre parosteal osteochondromatous proliferation (BPOP) is also known as Nora's disease. It is a benign lesion. Even though recent studies showed probable neoplastic etiology, the exact cause is unknown. BPOP commonly involves small bones of hands and feet. This condition is rare and very few cases are reported. In this report, two cases are presented with clinical, radiological, and histopathological findings. The first case was a 38-year-old female presented with 3-year history of mild painful swelling in the left middle finger and the second case was a 28-year-old male with the left leg swelling for 8 years. On radiology, both cases showed surface lesion with uninvolved medullary cavity. Excision specimen of both the lesions subjected for histopathological examination. Microscopically, there was irregular maturation of the bone and cartilage. Cartilage showed purplish-blue color (blue bone) with bizarre chondrocytes. BPOP is a rare benign condition. Awareness of clinical radiological and microscopic findings is needed for correct diagnosis and to differentiate it from other mimicking benign and malignant conditions.

Identification of COL1A1/2 Mutations and Fusions With Noncoding RNA Genes in Bizarre Parosteal Osteochondromatous Proliferation (Nora Lesion)

Bizarre parosteal osteochondromatous proliferation (BPOP) (Nora lesion) is a benign bone surface lesion, which most commonly occurs in the digits of young patients and has a high rate of recurrence. Histologically, it is composed of a mixture of disorganized bone, cartilage, and spindle cells in variable proportions and characterized by amorphous "blue bone" mineralization. Recurrent chromosomal abnormalities, including t(1;17)(q32-42;q21-23) and inv(7)(q21.1-22q31.3-32), have been reported in BPOP. However, the exact genes involved in the rearrangements remain unknown. In this study, we analyzed 8 BPOP cases affecting the fingers, toe, ulna, radius, and fibula of 5 female and 3 male patients, aged 5 to 68 years. RNA sequencing of 5 cases identified genetic fusions between COL1A2 and LINC-PINT in 3 cases and COL1A1::MIR29B2CHG fusion in 1, both validated using fluorescence in situ hybridization and reverse transcription (RT)-PCR. The remaining fusion-negative case harbored 3 COL1A1 mutations as revealed by whole-exome sequencing and confirmed using Sanger sequencing. All these genetic alterations were predicted to cause frameshift and/or truncation of COL1A1/2. The chromosomal locations of COL1A2 (7q21.3), LINC-PINT (7q32.3), COL1A1 (17q21.33), and MIR29B2CHG (1q32.2) were consistent with the breakpoints identified in the previous cytogenetic studies. Subsequent screening of 3 BPOPs using fluorescence in situ hybridization identified 1 additional case each with COL1A1 or COL1A2 rearrangement. Our findings are consistent with reported chromosomal abnormalities and implicate the disruption of type I collagen, and perhaps of either noncoding RNA gene as a tumor suppressor, in the tumorigenesis of BPOP. The prevalence and tumorigenic mechanisms of these COL1A1/2 alterations in BPOP require further investigation.

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's Lesion) of the Foot: A Case Report and Literature Review of Nora's Lesion of the Foot

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

Subungual Exostosis on the Right Hallux

Subungual exostosis (SE) is a benign, relatively uncommon bony growth underneath the nails of the distal phalanx of toes or fingers, with a majority on the toes. Clinically, it has two subvariants-protruded and nonprotruded growths from nail plates-which are treated differently. In this article, we report a case of protruded SE in a teenager with illustrative surgical excision. A 15-year-old boy presented with a painful growth on his right great toe of 6 months' duration. Physical examination revealed a 1-cm-diameter, solid, erythematous, rough, irregular growth penetrating through the skin along the dorsolateral nail bed of the right hallux with deformity of the lateral nail plate. Radiographs showed an elevated mass over the distal phalanx of the right lateral hallux. The mass was surgically excised and histopathologic examination confirmed the diagnosis of SE. The patient had no relapse or recurrence at follow-ups of 6 and 18 months. Subungual exostosis is a relatively uncommon bony growth in the toes. Radiography is favored for the diagnosis. Complete surgical excision is the optimal treatment, with rare recurrence. It needs to be differentiated from other bony lesions, including bizarre parosteal osteochondromatous proliferation, myositis ossificans, fibro-osseous pseudotumor, osteochondroma, and enchondroma.

Some Reactive Lesions of Bone Are Probably Neoplasms: A Review

CONTEXT.—

A number of fibro-osseous and osteocartilaginous lesions, especially common in the small bones of hand and feet, pose a diagnostic challenge and have historically been thought to be reactive lesions. However, modern molecular techniques when supplementing clinical, radiographic, and histologic evaluation suggest they may, in fact, be neoplasms.

OBJECTIVE.—

To review the clinical presentation and histopathologic, molecular, and radiologic features of selective bone lesions, focusing most specifically on subungual exostosis, florid reactive periostitis, and bizarre periosteal osteochondromatous proliferation.

DATA SOURCES.—

Literature review and personal experience are the source of this review.

CONCLUSIONS.—

Some lesions previously thought to be reactive are locally aggressive and demonstrate reproducible molecular abnormalities, and thus may be neoplasms. Although most common in the bones of the fingers and toes, these lesions also occur in long and other bones. The clinical presentations, radiologic appearances, and histopathologic features often overlap, making the diagnosis challenging, and these lesions may require molecular evaluation to maximize accurate prognostication.

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) 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.

[Updates to the WHO classification of bone tumours]

The fourth edition of the WHO Classification of Soft Tissue and Bone Tumours, published in 2013, extends the approach to describe genetics and pathology of these tumours in the context of epidemiological, clinical and imaging data, which was adopted in the third edition. Added are a few new entities, reclassifications and renamings. The most important point, also of clinical relevance and with consequences for treatment, is the introduction of a stratification of bone tumours based on their biological behaviour into three groups (benign, intermediate, malignant) in analogy to soft tissue tumours.

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.

Subungual Exostosis Systematic Review and Meta-Analysis

BACKGROUND

The coexistence of deformity of the nail bed and subungual exostosis (SE) is a frequent finding in podiatric practice in the fourth and fifth decades of life. However, it has been described by other specialists as being an uncommon osteocartilaginous tumor most prevalent during the second and third decades of life. This study attempts to determine the causes of this discrepancy.

METHODS

Two authors independently conducted a systematic bibliographic review in multiple databases, podiatry sources and others, and key words were chosen to achieve a broad search strategy. Studies reporting on epidemiology and treatment of SE lesions in lower extremities in ten or more patients were selected. Initially, 197 articles were identified through database screening, with 23 meeting all inclusion and exclusion criteria. Seven articles with the ages of all of the patients were included in the analysis of age data. A comparison was then made between the diagnostic criteria for the selected 23 articles.

RESULTS

Model results reveal that, although there are some significant differences between individual studies, the main factor tested (patient's age) was clearly significant ( F_1,5.2 = 78.12, P < .001), showing that studies coming from the podiatry speciality were conducted on individuals with a mean age of 37 years higher than in studies from other specialties. Clinical and radiologic characteristics and treatment described in the podiatry literature also contrast with those in other specialties.

CONCLUSIONS

The SE described by podiatrists, in accordance with the parameters of true exostosis, is different from Dupuytren's SE and should be considered as a different pathologic entity. The authors are working on its histologic identification.

Conditions Simulating Primary Bone Neoplasms

A number of nonneoplastic conditions can mimic tumors of bone. Some of the more common mimics of primary bone tumors include infectious, inflammatory, periosteal, and degenerative joint disease-associated lesions that produce tumorlike bone surface-based or intraosseous lesions. This article considers a spectrum of reactive and nonreactive processes including stress fracture, subchondral cysts, osteonecrosis, heterotopic ossification, osteomyelitis, sarcoidosis, and amyloidoma that can present in such a way that they are mistaken for a tumor arising primary in bone.

Bizarre parosteal osteochondromatous proliferation: a novel case report of recurrence in the toe

Bizarre parosteal osteochondromatous proliferation (BPOP) is an uncommon reactive mesenchymal lesion mainly affecting the small bones of the hands and feet. They frequently occur in young adults. It is important to understand and differentiate BPOP from other lesions, especially because of its atypical microscopic features and tendency to recur. We present a case of a recurrent lesion involving the toe and discuss management options. To our knowledge, our current case report is the first in the literature to report a recurring BPOP lesion of the toe.

[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".

Refinements in Sarcoma Classification in the Current 2013 World Health Organization Classification of Tumours of Soft Tissue and Bone

The fourth edition of the World Health Organization (WHO) Classification of Tumours of Soft Tissue and Bone was published in February 2013. The 2013 WHO volume provides an updated classification scheme and reproducible diagnostic criteria, which are based on recent clinicopathologic studies and genetic and molecular data that facilitated refined definition of established tumor types, recognition of novel entities, and the development of novel diagnostic markers. This article reviews updates and changes in the classification of bone and soft tissue tumors from the 2002 volume.

Subungual fibro-osseous pseudotumour of the toe

Subungual fibro-osseous pseudotumour of the toe is a rare osseous soft tissue tumour of which only six cases have been described in the literature. We present a case in a teenage boy that posed an instructive diagnostic challenge and discuss the distinguishing features of the various differential diagnoses. The subungual location is very rare. For such tumours, radiology is as vital as histopathology in making a diagnosis and excluding neoplasia. Accurate diagnosis requires careful clinico-pathological and radiological correlation. These sorts of lesions may present to the dermatologist, not always the foot surgeon.

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.

Incidence, histopathologic analysis and distribution of tumours of the hand

Background

The aim of this large collective and meticulous study of primary bone tumours and tumourous lesions of the hand was to enhance the knowledge about findings of traumatological radiographs and improve differential diagnosis.

Methods

This retrospective study reviewed data collected from 1976 until 2006 in our Bone Tumour Registry. The following data was documented: age, sex, radiological investigations, tumour location, histopathological features including type and dignity of the tumour, and diagnosis.

Results

The retrospective analysis yielded 631 patients with a mean age of 35.9 ± 19.2 years. The majority of primary hand tumours were found in the phalanges (69.7%) followed by 24.7% in metacarpals and 5.6% in the carpals. Only 10.6% of all cases were malignant. The major lesion type was cartilage derived at 69.1%, followed by bone cysts 11.3% and osteogenic tumours 8.7%. The dominant tissue type found in phalanges and metacarpals was of cartilage origin. Osteogenic tumours were predominant in carpal bones. Enchondroma was the most commonly detected tumour in the hand (47.1%).

Conclusions

All primary skeletal tumours can be found in the hand and are most often of cartilage origin followed by bone cysts and osteogenic tumours. This study furthermore raises awareness about uncommon or rare tumours and helps clinicians to establish proper differential diagnosis, as the majority of detected tumours of the hand are asymptomatic and accidental findings on radiographs.

Subungual exostosis of the toes: a systematic review

BACKGROUND

Subungual exostosis is a relatively common benign bone tumor that occurs in the distal phalanges of the toes and can be a source of pain and nail deformity. There is controversy about the treatment of these lesions and there are few studies that have synthesized what is known and provided meaningful information on treatment.

QUESTIONS/PURPOSES

We performed a systematic review to address the following questions: (1) What is the best surgical approach for excising these lesions? (2) What is the age range, sex distribution, and presenting symptoms of subungual exostoses and which toe is most frequently affected? (3) What complications arise from treatment?

METHODS

Two authors independently searched multiple databases (Medline, 1950-May 2013; Cochrane EBM database, and EMBASE, 1980-May 2013 provided by OVID; ACP Journal Club, 2003-May 2013; CINAHL by EBSCO, 1937-May 2013; and PubMed by NLM, 1940-May 2013), and key words were chosen to achieve a broad search strategy. We included studies on the management of toe exostoses with > 10 cases and we excluded studies that reported on upper extremity exostoses or osteochondromas. Demographic and treatment data were collected from each article by two independent authors and collated. A total of 124 abstracts were screened, and 116 articles were reviewed in full, of which 13 met the inclusion criteria.

RESULTS

Complete marginal excision through a fish mouth incision protecting the nail led to a recurrence rate of 4% and satisfactory clinical results, defined as no requirement for postoperative intervention and a satisfactory clinical appearance in 73%. Most studies provided incomplete descriptions of specific surgical techniques used. Fifty-five percent of the patients were younger than 18 years of age. A history of toe trauma before diagnosis was present in approximately 30% of the cases. Delayed diagnosis occurred in approximately 10% of the cases and onychodystrophy occurred in more than 10%.

CONCLUSIONS

There is weak evidence to guide management of subungual exostosis. Adequate wound management postexcision aiming to minimize disruption to the nail bed and matrix may prevent onychodystrophy, which is a common complication of 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.

Bizarre parosteal osteochondromatous proliferation with an inversion of chromosome 7

Bizarre parosteal osteochondromatous proliferation (BPOP) is a benign exophytic proliferative lesion that predominantly involves the small tubular bones of the hands and feet. Histologically BPOP is characterized by a heterogeneous mixture of cartilage, bone and fibrous tissue. Recently, a translocation between chromosomes 1 and 17, or its variant translocations, has been reported to be unique in BPOP. The case of a 59-year-old woman with BPOP in the middle phalanx of the ring finger with increasing mass is reported herein. Computed tomography and magnetic resonance imaging depicted the central part of the exophytic bone lesion as having continuity to the underlying bone marrow, which is considered to be the typical finding of osteochondroma, but not a common finding in BPOP. In addition, an inversion of chromosome 7 [inv (7)(q22q32)] was observed. Therefore, this case suggests that the translocation between chromosomes 1 and 17 reported in other cases may not be the only cause of BPOP.

Bizarre parosteal osteochondromatous proliferation of bone: clinical management of a series of 22 cases

We describe 22 cases of bizarre parosteal osteochondromatous proliferation, or Nora's lesion. These are surface-based osteocartilaginous lesions typically affecting the hands and feet. All patients were identified from the records of a regional bone tumour unit and were treated between 1985 and 2009. Nine lesions involved the metacarpals, seven the metatarsals, one originated from a sesamoid bone of the foot and five from long bones (radius, ulna, tibia, and femur in two). The mean age of the patients was 31.8 years (6 to 66), with 14 men and eight women. Diagnosis was based on the radiological and histological features. The initial surgical treatment was excision in 21 cases and amputation of a toe in one. The mean follow-up was for 32 months (12 to 162). Recurrence occurred in six patients (27.3%), with a mean time to recurrence of 49 months (10 to 120). Two of the eight patients with complete resection margins developed a recurrence (25.0%), compared with four of 14 with a marginal or incomplete resection (28.6%). Given the potential surgical morbidity inherent in resection, our data suggest that there may be a role for a relatively tissue-conserving approach to the excision of these lesions.

Reactive bone lesions mimicking neoplasms

Reactive lesions of bone and soft tissue can appear alarming on histologic examination because they are often cellular and have atypical (activated) cytologic features, such as distinct nucleoli and mild hyperchromasia, and mitotic activity. Reactive lesions of bone and periosteum also produce bone and cartilage matrix, resulting in confusion with osteosarcoma or chondrosarcoma. Careful attention to key cytomorphological features such as the pattern of bone formation, uniform appearance of cells, and absence of atypical mitoses should help identify the reactive nature of a lesion. Correlation with clinical and radiological findings is also imperative to avoid misclassification of the tumor because reactive lesions often arise at sites where osteosarcoma and chondrosarcoma are rare (e.g., the hand) and lack aggressive radiological features. In this review we discuss reactive lesions of bone that are commonly confused with malignant neoplasms and that the practicing pathologist is likely to encounter at some point. Several of these lesions have had characteristic chromosomal translocations documented in recent years, but continue to be included as reactive lesions based on their overall clinicopathological features.

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.

[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.

Advances in the identification of molecular markers for bone neoplasia

IMPORTANCE OF THE FIELD

Bone tumors represent a heterogeneous and poorly understood group of neoplasms affecting patients of all ages. This review is intended to highlight recent advances in the identification of diagnostically relevant molecular biomarkers.

AREAS COVERED IN THIS REVIEW

This review offers a summary of basic techniques in molecular pathology. In the case of primary bone tumors with diagnostically applicable molecular markers, an overview of the tumor is provided incorporating the germane background and advances in the identification of molecular markers.

WHAT THE READER WILL GAIN

The reader will gain an understanding of the techniques governing the discovery of biomarkers, and their applicability in diagnostic bone pathology.

TAKE HOME MESSAGE

Molecular analysis has identified key diagnostic biomarkers in only a small proportion of bone tumors. Many of these findings owe their existence to earlier karyotype-based cytogenetic studies. In cases where characteristic cytogenetic findings are absent, there remains a tremendous need to interrogate rigorously these lesions using emerging techniques such as whole genome sequencing. It is assumed that with a more precise understanding of the tumor genetic code, more accurate diagnostic, prognostic and therapeutic markers will emerge.

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.

Chromosomal rearrangements in lipofibromatosis

Lipofibromatosis is a relatively rare pediatric neoplasm, which usually manifests as an ill-defined soft tissue mass involving the upper and lower distal extremities, the trunk, and, less frequently, the head. To date, no cytogenetic abnormalities have been reported in this uncommon neoplasm. We present a case of lipofibromatosis featuring a three-way t(4;9;6) translocation in a 5-year-old boy.

Solid variant of aneurysmal bone cyst with a novel (X;9) translocation

Aneurysmal bone cysts (ABC) are locally destructive bone lesions occurring predominantly in young adults. There has been debate as to the neoplastic nature of these lesions. In recent years, however, compelling evidence of clonal chromosomal abnormalities has indicated a likely neoplastic origin. Although relatively few ABC have been assessed cytogenetically, many of those which have been studied have shown abnormalities of chromosome 17, particularly t(16;17)(q22;p13). We present a case of ABC in a 4-year-old female, which demonstrated the novel translocation t(X;9)(q26;q32).

La lésion de Nora ou Bizarre Parosteal Osteochondromatous Proliferation

The lesion Nora described in 1983 as a bizarre parosteal osteochondromatous proliferation (BPOP) is a member of a group of osteocartilaginous surface lesions. BPOP is infrequent but new cases are regularly reported. We report two new cases with an unusual localization (ilion and distal humerus) and unusual size (9 cm for the iliac lesion). In light of these cases and reports in the literature, the main differential diagnoses of BPOP are exostosis and parosteal osteosarcoma.

Bizarre parosteal osteochondromatous proliferation of the proximal humerus: case report

Bizarre parosteal osteochondromatous proliferation (BPOP), or Nora's lesion, is a rare lesion of bone occurring predominantly in the long bones of the hands and feet. It exists as a puzzling clinical entity of uncertain origins and high recurrence rates after surgical resection. To our knowledge, this clinical entity has not been reported in the proximal aspect of the humerus. An interesting report of a lesion occurring in the proximal humerus, which initially was misinterpreted as a parosteal osteosarcoma, is discussed outlining the clinical, radiographic and pathologic features of the BPOP lesion.

Molecular pathology of chondroid neoplasms: part 1, benign lesions

This two-part review presents an overview of the molecular findings associated with both benign and malignant chondroid neoplasms. This first part presents a brief review of methods in molecular pathology along with a review of the cytogenetic and molecular genetic findings in benign chondroid neoplasms. Clinical aspects of the various lesions are briefly discussed, and each tumor is illustrated with representative radiographic and pathologic images. Malignant chondroid neoplasms will be considered in the second part of this review.

Rearrangement of the COL12A1 and COL4A5 genes in subungual exostosis: molecular cytogenetic delineation of the tumor-specific translocation t(X;6)(q13-14;q22)

Subungual exostosis is a benign bone- and cartilage-producing tumor occurring in the hands and feet of children and young adults. The recent identification of a recurrent chromosomal translocation t(X;6)(q24-q26;q15-21) in short-term-cultured tumor cells strongly suggests that subungual exostosis is a neoplastic lesion caused by rearrangement of genes in the two breakpoints. To identify the genes that are critical for neoplastic transformation, we have studied five subungual exostoses by interphase or metaphase FISH. The results of these analyses demonstrated a clustering of the breakpoints to the regions harboring the collagen genes COL12A1 and COL4A5 in chromosome bands 6q13-14 and Xq22, respectively. Furthermore, in all but one case, these two genes were shown to colocalize on the derivative chromosomes X and 6, strongly suggesting that at least one of them is consistently involved in the formation of a chimeric fusion gene or in the exchange of regulatory sequences. Because collagen molecules are important for tissue remodeling during physiologic growth and differentiation, both COL12A1 and COL4A5 constitute good candidate target genes in the pathogenesis of subungual exostosis. Further investigations on the transcript level are required to elucidate the functional outcome of the t(X;6) translocation in subungual exostoses.

Heterotopic ossification: a review

Heterotopic ossification is the formation of bone in the soft tissues. Soft tissue bone deposition may range from the minimal and inconsequential to massive and clinically significant. In some clinical settings it is a predictable finding with an unpredictable course and in other settings it may be diagnostically confounding. Heterotopic ossification may be encountered in clinically disparate disease processes and circumstances. We review the genetic, neurogenic, post-traumatic, post-surgical and "reactive" causes of heterotopic ossification and discuss some current concepts of its pathogenesis.

Bizarre parosteal osteochondromatous proliferation with a t(1;17) translocation

Bizarre parosteal osteochondromatous proliferation (BPOP) is a benign lesion that tends to recur repeatedly. Histologically, BPOP contains three components (cartilage, bone, and spindle cells) in differing amounts. The histological findings of BPOP are similar to those of florid reactive periostitis (FRP) and subungual (Dupuytren's) exostosis. Some authors have postulated that all of these conditions are reactive proliferative lesions representing different phases of reactive processes. Whether BPOP is a reactive proliferative lesion or a neoplastic lesion, however, remains controversial. Recently, a t(1;17)(q32;q21) translocation in BPOP was detected using chromosome banding and fluorescence in situ hybridization (FISH) analyses. Here, we describe a 39-year-old Japanese female with BPOP arising in the proximal phalanx of her third toe. A cytogenetic analysis revealed a t(1;17)(q 42;q23) translocation. The breakpoints in this case are located close to those of previously reported cases. These results suggest that t(1;17) is a distinct translocation of BPOP and that BPOP is a neoplastic lesion, rather than a reactive proliferative process.