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

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

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

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

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

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

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) Of the Second Proximal Phalanx Encasing the Flexor Tendon of the Foot: A Case Report.

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

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.

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's Lesion) in the Hand: A Case Report and a Review of the Literature.

A Nora's lesion, a rare and typically non-cancerous growth originating from the parosteal osteochondromatous tissue, primarily manifests in the hands and feet. Despite its benign nature, diagnosing Nora's lesions is complex due to their tendency to exhibit aggressive features in imaging scans and the ambiguity encountered in histological examinations. This rarity is evidenced by the limited number of reported cases in medical literature since its initial discovery. Detailing a distinctive instance, we document a specific case of a Nora's lesion situated on the dorsum of the left hand, specifically above the shafts of the fourth and fifth metacarpal bones. Through a meticulous histopathological analysis, the diagnosis was confirmed, aligning precisely with imaging features. To address the lesion conclusively, a comprehensive surgical excision of the mass was performed. This particular case not only adds to the scant body of documented instances but also underscores the significance of accurate diagnosis and management. Understanding and documenting such cases are crucial in refining diagnostic approaches and optimizing treatment strategies for Nora's lesions, emphasizing the ongoing need for further research in this domain.

Nora Lesion (Bizarre Parosteal Osteochondromatous Proliferation): An Ultrasound Diagnosis with Magnetic Resonance Imaging Correlation.

Advanced cross-sectional imaging techniques are firmly established as a means of evaluating musculoskeletal disease, and ultrasound (US) is increasingly being used for the assessment of a diversity of tendon, joint, and soft-tissue abnormalities. A benign condition - bizarre parosteal osteochondromatous proliferation (BPOP) - arises from the periosteum, typically in the small bones of the hands and feet, and grows as a surface bone lesion in the surrounding soft tissue. Proliferations can become symptomatic, exercising mass effect on adjacent structures that may require operative management. As a bone-forming process, BPOP may occasionally assume worrisome histologic features that mimic sarcoma, and a pronounced tendency to recur after primary excision. A solitary mass was growing in the middle finger of a young woman that curtailed proper hand function. With US, a partially ossified formation was revealed in the proximal phalanx situated on the outer surface of the bone. There was faint acoustic shadowing distal to the lesion, and a hypoechoic halo was seen covering part of the abnormal tissue growth. Importantly, the lesion caused significant limitation of motion of the finger, on the dynamic flexion US images with the displacement of the flexor tendon and compression of a digital nerve. To restore the range of motion in the finger, surgical excision of the juxtacortical mass was performed and histology yielded a diagnosis of BPOP. We describe the US features of digital BPOP, which were found to correspond closely to those of computed tomography and magnetic resonance imaging.

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.

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.

Nora's lesion of the distal ulna: a case report.

Nora's lesion, also known as bizarre parosteal osteochondromatous proliferation (BPOP), is a very rare benign lesion with few published cases. BPOP is more common in adults during the second to third decades of life, and usually occurs on the hands and feet. Radiologically, it appears as a calcified mass attached to the bone cortex that grows rapidly and that recurs easily following resection. Aggressive features on imaging and confusing histopathological findings usually result in misdiagnosis or mistreatment. Herein, we present a case of a rare bony tumour involving the distal ulna presenting as a painless growing mass. An excisional biopsy with clear margins was performed without disturbing the ulnar nerve and arteries. There was no recurrent mass or calcified lesion 1 year after surgery. Based on its rarity and difficult diagnosis, BPOP should be considered in the differential diagnosis of a painless mass in the distal ulnar region. Careful follow-up after surgery is essential, even without lesion recurrence.

Disruption of Jmjd3/p16Ink4a Signaling Pathway Causes Bizarre Parosteal Osteochondromatous Proliferation (BPOP)-like Lesion in Mice.

Bizarre parosteal osteochondromatous proliferation (BPOP), or Nora's lesion, is a rare benign osteochondromatous lesion. At present, the molecular etiology of BPOP remains unclear. JMJD3(KDM6B) is an H3K27me3 demethylase and counteracts polycomb-mediated transcription repression. Previously, Jmjd3 was shown to be critical for bone development and osteoarthritis. Here, we report that conditional deletion of Jmjd3 in chondrogenic cells unexpectedly resulted in BPOP-like lesion in mice. Biochemical investigations revealed that Jmjd3 inhibited BPOP-like lesion through p16Ink4a . Immunohistochemistry and RT-qPCR assays indicated JMJD3 and p16INK4A level were significantly reduced in human BPOP lesion compared with normal subjects. This was further confirmed by Jmjd3/Ink4a double-gene knockout mice experiments. Therefore, our results indicated the pathway of Jmjd3/p16Ink4a may be essential for the development of BPOP in human. © 2021 American Society for Bone and Mineral Research (ASBMR).

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: Rare case affecting distal ulna and review of literature.

Bizarre parosteal osteochondromatous proliferation (BPOP) or Nora's lesion, is a rare benign surface-based bone lesion most commonly involving the tubular bones of hands and feet. We report an unusual case of BPOP affecting the distal ulna in a 22-year-old man who presented with a painless wrist mass following injury and was successfully treated with surgical resection. We focus on multi-modality imaging, histopathology, and differential diagnosis (including osteochondroma, florid reactive periostitis, myositis ossificans, and surface-type osteosarcoma), as well as a review of the literature regarding recent concepts on etiology and evolution, spectrum of imaging characteristics and diagnostic overlap, histopathology, as well as treatment options.

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 co-occurring with a metatarsal fatigue fracture: a case report.

BACKGROUND: Bizarre parosteal osteochondromatous proliferation (BPOP) is a relatively rare benign extraperiosteal osteochondroma-like proliferative lesion that shares similarities with malignant tumours in terms of morphology. The aetiology of BPOP has yet to be determined and there are no previous reports of BPOP associated with fracture. CASE PRESENTATION: A 57-year-old woman presented with a one-month history of pain and swelling in her right foot, which were worsened by activity and improved with rest. Physical examination revealed a hard, non-mobile mass measuring 1.5 cm × 1.5 cm on the dorsal aspect of the third metatarsal of the right foot. There was overlying erythema and tenderness on palpation. Computed tomography (CT) of the right foot demonstrated a fracture of the neck of the third metatarsal, osteolysis at the fracture site and soft tissue swelling. Bone scintigraphy revealed increased tracer uptake suggesting abnormal bone metabolism at the neck of the third metatarsal. Surgical excision of the lesion was performed. Histopathology and immunohistochemistry confirmed the diagnosis of BPOP. CONCLUSION: BPOP is a rare benign lesion that is commonly misdiagnosed. Differential diagnosis is mainly achieved through imaging and histopathological assessment.