Metaphysis Of Long Bones Research Articles

Pediatric Bone Tumors: Location and Age Distribution of 420 Cases

Background/Objectives: One of the most important diagnostic tools in bone tumors is X-rays. Preliminary and, in the case of some benign lesions, definitive diagnoses are formed using this basic tool. Part of the decision making in this stage is based on statistical probability using the patient’s age, as well as the incidence and predilection sites of different entities. The information used today is based on older and fragmented data. To verify the underlying principles, we retrospectively evaluated all bone tumors in children and adolescents treated by our tertiary center in the last 20 years. Methods: For this retrospective study, patients under the age of 18 years suffering from histopathologically verified bone tumors were evaluated. Data were retrieved from our local musculoskeletal tumor database. Results: We were able to include 420 children treated for bone tumors in our tertiary center. The cohort consisted of 335 benign and 85 malignant lesions. The most common lesions were 137 osteochondromas; the malignant tumors consisted mainly of osteosarcomas (53) and Ewing’s sarcomas (28). The primary predilection sites were the metaphyses of long bones. Conclusions: We were able to confirm and supplement the fragmentary data of these rare diseases using our own cohort.

A rare case of trapezium osteochondroma: unveiling a unique tumour with clinical implications

Osteochondroma is a benign bone tumour commonly found on the metaphysis of long bones. The presentation of osteochondroma on the trapezoid bone, a carpal bone in the wrist, is exceptionally rare. To our knowledge, no such cases have been reported in India. This report details a rare case of osteochondroma located on the trapezoid bone and its successful surgical management. A 55-year-old female presented with pain and swelling in the wrist. Radiological imaging, including X-rays and MRI, revealed a well-defined, pedunculated mass arising from the trapezoid bone. The patient underwent surgical resection of the tumour. Histopathological examination confirmed the diagnosis of osteochondroma. Postoperatively, the patient experienced significant relief from symptoms and showed no evidence of tumour recurrence during follow-up. This case contributes to the limited body of literature on osteochondromas in rare locations, particularly on the trapezoid bone. It illustrates the successful outcome of surgical treatment for rare bone tumours and emphasizes the need for heightened awareness and comprehensive diagnostic approaches in similar cases.

Hereditary multiple exostoses

Hereditary multiple exostoses is a rare congenital condition with autosomal dominant inheritance. It consists of formation of osteocartilaginous exostoses, most commonly from the metaphysis of long bones. Surgery is the main treatment as there is no available medical treatment. Clinical follow-ups with orthopaedic specialists are important, both in childhood and adulthood. In childhood, focus is on managing symptoms and removing symptomatic exostoses, while in adulthood, MRI is performed to rule out malignant transformation, as argued in this review.

Novel EXT1 variants cause divergent symptom severity in multiple cartilaginous exostoses: a family report

Abstract Background Multiple cartilaginous exostoses (MCE) are a rare genetic disorder characterized by multiple osteochondromas in the metaphysis of long bones. Case Presentation. We report a 15-year-old male patient, his father, and his brother, all presenting varied severity of the same symptom. The patient exhibited symptoms since infancy, with osteochondromas affecting mobility and causing joint deformities. Whole exome sequencing identified a pathogenic NM_000127.3(EXT1):c.1056 + 2 T > G and a likely pathogenic NM_000127.3(EXT1):c.1047G > T variant in the EXT1 gene, both novel. Conclusions Despite three decades since the discovery of the EXT1 gene, MCE diagnosis may be delayed until adolescence or adulthood. This report contributes to clinical understanding, emphasizing the importance of early diagnosis, genetic analysis, and potential treatment approaches, to mitigate long-term deformities and complications in MCE patients.

Aneurysmal bone cyst of the greater trochanter: evaluation of surgical outcome of 17 cases

Background: Aneurysmal bone cyst is a benign, aggressive lesion that occurs in childhood and early adulthood. It usually affects the metaphysis of long bones. The aims of this study were to report clinical and radiological outcome following operative treatment of aneurysmal bone cyst of greater trochanter of femur and asses functional outcome by the Musculoskeletal Tumour Society (MSTS) Rating scale for the lower extremity. Methods: This Quasi-experimental study included 17 patients radiologically and histologically diagnosed as having aneurysmal bone cyst involving the greater trochanter of femur from 2015 to 2022. All cases were curetted, chemical cauterization with 5% phenol done and autogenous cortico-cancellous bone graft were added to fill the osseous defect. The patients were followed-up at 6 weeks and then 3 monthly for 1st year, 6 monthly for 2nd and 3rd year and yearly thereafter. In each follow-up, the recurrence, post-operative complications were documented and MSTS scoring was done. Results: The mean age of the patients were 14.5 years; 9 (53%) were female and 8 (47%) were male. The mean follow-up period for the patients was 3.6 years. There were 3 (18%) recurrences and 2 (11.8%) cases developed superficial surgical site infection. The average MSTS score on final follow-up was 22.6. Conclusion: Aneurysmal bone cyst of the greater trochanter is common in second decade among females. Treatment with extended intralesional curettage, chemical cauterization with 5% phenol and application of autogenous bone graft has less than 18% chance of recurrence. Furthermore, there is acceptable radiological bone graft incorporation and average MSTS score on final follow-up suggest a good functional outcome. BIRDEM Med J 2024; 14(3): 124-130

A Case of Hereditary Multiple Exostoses: Role of FNAC in diagnosis

Abstract Hereditary Multiple Exostoses (HME) is a rare autosomal dominant bone disease. It is characterized with numerous benign osteochondromas, which grow outward from the metaphyses of long bones. In many cases it is asymptomatic but can lead to considerable number of complications, like pressure symptoms, limb deformities, and can cause psychosocial problems. Malignant transformation is rarely seen. Surgery is the main modality of treatment.This paper aims to highlight the role of FNAC in diagnosis of HME.

ENPP1 enzyme replacement therapy improves ectopic calcification but does not rescue skeletal phenotype in a mouse model for craniometaphyseal dysplasia.

Craniometaphyseal dysplasia (CMD) is a rare genetic bone disorder, characterized by progressive thickening of craniofacial bones and flared metaphyses of long bones. Craniofacial hyperostosis leads to the obstruction of neural foramina and neurological symptoms such as facial palsy, blindness, deafness, or severe headache. Mutations in ANKH (mouse ortholog ANK), a transporter of small molecules such as citrate and ATP, are responsible for autosomal dominant CMD. Knock-in (KI) mice carrying an ANKF377del mutation (AnkKI/KI ) replicate many features of human CMD. Pyrophosphate (PPi) levels in plasma are significantly reduced in AnkKI/KI mice. PPi is a potent inhibitor of mineralization. To examine the extent to which restoration of circulating PPi levels may prevent the development of a CMD-like phenotype, we treated AnkKI/KI mice with the recombinant human ENPP1-Fc protein IMA2a. ENPP1 hydrolyzes ATP into AMP and PPi. Male and female Ank+/+ and AnkKI/KI mice (n ≥ 6/group) were subcutaneously injected with IMA2a or vehicle weekly for 12wk, starting at the age of 1wk. Plasma ENPP1 activity significantly increased in AnkKI/KI mice injected with IMA2a (Vehicle/IMA2a: 28.15 ± 1.65/482.7 ± 331.2 mOD/min; p <.01), which resulted in the successful restoration of plasma PPi levels (Ank+/+ /AnkKI/KI vehicle treatment/AnkKI/KI IMA2a: 0.94 ± 0.5/0.43 ± 0.2/1.29 ± 0.8μM; p <.01). We examined the skeletal phenotype by X-Ray imaging and μCT. IMA2a treatment of AnkKI/KI mice did not significantly correct CMD features such as the abnormal shape of femurs, increased bone mass of mandibles, hyperostotic craniofacial bones, or the narrowed foramen magnum. However, μCT imaging showed ectopic calcification near basioccipital bones at the level of the foramen magnum and on joints of AnkKI/KI mice. Interestingly, IMA2a treatment significantly reduced the volume of calcified nodules at both sites. Our data demonstrate that IMA2a is sufficient to restore plasma PPi levels and reduce ectopic calcification but fails to rescue skeletal abnormalities in AnkKI/KI mice under our treatment conditions.

Activation of NF-κB signaling regulates ovariectomy-induced bone loss and weight gain

Postmenopausal women experience bone loss and weight gain. To date, crosstalk between estrogen receptor signals and nuclear factor-κB (NF-κB) has been reported, and estrogen depletion enhances bone resorption by osteoclasts via NF-κB activation. However, it is unclear when and in which tissues NF-κB is activated after menopause, and how NF-κB acts as a common signaling molecule for postmenopausal weight gain and bone loss. Therefore, we examined the role of NF-κB in bone and energy metabolism following menopause. NF-κB reporter mice, which can be used to measure NF-κB activation in vivo, were ovariectomized (OVX) and the luminescence intensity after OVX increased in the metaphyses of the long bones and perigonadal white adipose tissue, but not in the other tissues. OVX was performed on wild-type (WT) and p65 mutant knock-in (S534A) mice, whose mutation enhances the transcriptional activity of NF-κB. Weight gain with worsening glucose tolerance was significant in S534A mice after OVX compared with those of WT mice. The bone density of the sham group in WT or S534A mice did not change, whereas in the S534A-OVX group it significantly decreased due to the suppression of bone formation and increase in bone marrow adipocytes. Disulfiram, an anti-alcoholic drug, suppressed OVX-induced activation of NF-κB in the metaphyses of long bones and white adipose tissue (WAT), as well as weight gain and bone loss. Overall, the activation of NF-κB in the metaphyses of long bones and WAT after OVX regulates post-OVX weight gain and bone loss.

Analysis of a child with SPONASTRIME dysplasia due to compound heterozygous variants of TONSL gene

To explore the clinical features and genetic etiology of a child with SPONASTRIME dysplasia (SD). A 9-month-old female who had presented at the Linyi People's Hospital in August 2022 for short stature was selected as the study subject. Clinical data of the child were collected, and whole exome sequencing (WES) was carried out. Sanger sequencing was used for validating the candidate variants. The child has manifested short stature, mid-face hypoplasia, joint laxity, internal knee rotation, irregularities in the metaphysis of long bones, and flat and concave lumbar vertebrae. WES revealed that she has harbored compound heterozygous variants of the TONSL gene, namely c.3088G>T (p.Glu1030*) and c.3053G>A (p.Arg1018His), which were inherited from her phenotypically normal parents. Neither variant was reported previously. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the c.3088G>T variant was classified as likely pathogenic (PVS1+PM2_Supporting), whilst the c.3053G>A was classified as a variant of uncertain significance (PM2_Supporting+PM3+PP3). The c.3088G>T and c.3053G>A compound heterozygous variants of the TONSL gene probably underlay the pathogenesis in this patient. Above finding has facilitated the clinical diagnosis and genetic counseling for her family.

Osteomyelitis in a Paediatric Patient with Sub-periosteal Abscess, Septic Pulmonary Emboli and Pneumothorax: A Case Report

Osteomyelitis is an inflammatory disorder affecting bone and adjacent tissue that primarily arises from pyogenic bacteria, often involving the metaphysis of long bones in pediatric patients through hematogenous spread with the common pathogen being Staphylococcus aureus. Complications such as pathological fractures, sinus formation, and abscesses, may occur. Septic pulmonary embolism (SPE), a rare complication, can lead to infarctions and abscesses in pulmonary vessels. Pneumothorax secondary to SPE can also occur, emphasizing the importance of considering these complications in patients with features of sepsis.

ALPL regulates pro-angiogenic capacity of mesenchymal stem cells through ATP-P2X7 axis controlled exosomes secretion

BackgroundEarly-onset bone dysplasia is a common manifestation of hypophosphatasia (HPP), an autosomal inherited disease caused by ALPL mutation. ALPL ablation induces prototypical premature bone ageing characteristics, resulting in impaired osteogenic differentiation capacity of human bone marrow mesenchymal stem cells (hBMMSCs). As angiogenesis is tightly coupled with osteogenesis, it also plays a necessary role in sustaining bone homeostasis. We have previously observed a decrease in expression of angiogenesis marker gene CD31 in the metaphysis of long bone in Alpl+/− mice. However, the role of ALPL in regulation of angiogenesis in bone has remained largely unknown.MethodsExosomes derived from Normal and HPP hBMMSCs were isolated and identified by ultracentrifugation, transmission electron microscopy, and nanoparticle size measurement. The effects of ALPL on the angiogenic capacity of hBMMSCs from HPP patients were assessed by immunofluorescence, tube formation, wound healing and migration assay. exo-ELISA and Western Blot were used to evaluate the exosomes secretion of hBMMSCs from HPP, and the protein expression of VEGF, PDGFBB, Angiostatin and Endostatin in exosomes respectively.ResultsWe verified that ALPL ablation resulted in impaired pro-angiogenic capacity of hBMMSCs, accounting for reduced migration and tube formation of human umbilical vein endothelial cells, as the quantities and proteins composition of exosomes varied with ALPL expression. Mechanistically, loss of function of ALPL enhanced ATP release. Additional ATP, in turn, led to markedly elevated level of ATP receptor P2X7, which consequently promoted exosomes secretion, resulting in a decreased capacity to promote angiogenesis. Conversely, inhibition of P2X7 increased the angiogenic induction capacity by preventing excessive release of anti-angiogenic exosomes in ALPL deficient-hBMMSCs.ConclusionThe ALPL–ATP axis regulates the pro-angiogenic ability of hBMMSCs by controlling exosomes secretion through the P2X7 receptor. Thus, P2X7 may be proved as an effective therapeutic target for accelerating neovascularization in ALPL–deficient bone defects.

Low-grade central osteosarcoma with extraosseous dedifferentiation: a rare case.

Low-grade central osteosarcoma (LGCOS), which arises from the intramedullary cavity of the metaphysis of long bones, occasionally exhibits extraosseous spread. Approximately 10-30% of patients with LGCOS exhibit dedifferentiation, but it is rare to experience a primary tumor with a dedifferentiated component. A 38-year-old female patient presented with right knee pain for two months. Imaging studies revealed a bone mass with extraosseous involvement. Wide resection was performed, and pathologic examination led to the diagnosis of LGCOS with a dedifferentiated extraosseous lesion. A single defect in the bone cortex constituted the boundary between the low- and high-grade components. The extraosseous high-grade component included more tumor cells with p53 overexpression and more murine double minute 2 (MDM2) copies compared with the low-grade component. These genetic mutations and copy number alterations can be associated with malignant transformation of LGCOS.

Osteochondroma arising from posterior superior iliac spine: A case report of unusual cause of low back pain

Low-back pain is the most common symptom encountered in orthopaedic spine out-patient practice. In young adults, the usual causes are soft tissue injuries, myofascial pain, annular tear of the intervertebral disc, sacroiliitis and spondyloarthropathies. We report a case of 20-year-old skeletally mature male presenting with chronic low back pain who was treated symptomatically elsewhere. He presented to us for second opinion and upon clinical assessment, he was diagnosed to have osteochondroma arising from the right postero-superior iliac spine. Osteochondromas are osteo-cartilaginous benign tumour with 1% malignant potential seen in adolescents and young adults. They usually arise from the metaphysis of long bones around the knee and occasionally reported in humerus, spine and pelvis. These lesions are mostly asymptomatic and found incidentally. En-bloc excision of the tumor is recommended for symptomatic osteochondromas. Clinicians should be aware of atypical pelvic osteochondromas which can present as extra-spinal cause of chronic low back pain.

Chondromyxoid Fibroma In Skull: An Unusual Site

Chondromyxoid fibroma are the rarest of the benign cartilaginous neoplasms. Mostly it involves metaphysis of long bones, however, rarely can be found in calvarium / skull base. We report a case of a 30 year-old female who was referred to the Radiology Department at Shifa International Hospital, Islamabad with history of progression and gradual loss of vision in unilateral eye. The patient had contrast enhanced MRI of brain which showed a heterogeneously enhancing mass lesion abutting the clivus, CP angle and brain stem with internal areas of necrosis. Differentials of chordoma, meningioma and chondrosarcoma were given. The patient then underwent surgery which confirmed the mass to be chondromyxoid fibroma

A rare case of chondromyxoid fibroma of distal phalanx of great toe

Chondromyxoid fibroma (CMF) is rare benign tumour of bone which are due to incomplete cartilage differentiation and first described by Jaffe and Lichtensein in 1948. CMF’s constitutes for less than 1% of all bone tumors. Histopathology is diagnostic and CMF show lobulated areas of spindle shaped or stellate cells with hypocellular center of chondroid or myxoid material and periphery is hypercellular with abundant fibromyxoid tissue and few multinucleated osteoclasts like giant cell. CMFs are commonly seen in metaphysis of long bones including proximal tibia or distal femur. Short tubular bones of hand and feet are uncommon sites and toes constitutes less than 5% of the tumors. We present a case of chondromyxoid fibroma of distal phalanx of left great toe in 35 years old male patient.

Imaging features at the time of diagnosis of osteosarcoma and Ewing sarcoma in children

IntroductionOsteosarcoma and Ewing sarcoma are the most frequent malignant bone tumours in children. The aim of this study is to characterize clinical and radiological features at presentation of a large cohort of children with these diseases, radiological findings useful to differentiate them and the main prognostic factors. Material and methodsRetrospective analysis of clinical and imaging findings of 83 children diagnosed and treated of Ewing sarcoma and osteosarcoma in a paediatric hospital during a period of 10 years. ResultsBoth tumours showed aggressive radiological features such as permeative or moth-eaten margins, cortical disruption, discontinuous periosteal reaction, intense contrast uptake, tumoral necrosis and soft-tissue component. They differed in their location, osseous matrix and gender predilection. Osteosarcoma occurred more frequently in the metaphysis of long bones (62%) with a blastic appearance (53%). Ewing sarcoma showed a predilection for male patients (71%), occurred in flat bones (42%) and in the diaphysis of long bones (58%) with a lytic appearance (82%). 29% of children presented with primary metastasis, most frequently located in the lungs. Survival rates were 78% in OS and 76% in Ewing sarcoma. Metastatic disease, aggressive radiological features and low percentage of tumoral necrosis after neoadjuvant chemotherapy were associated with poor prognosis (p < 0.05). ConclusionsImaging can confidently diagnose malignant paediatric bone tumours in children and may differentiate Ewing sarcoma from osteosarcoma, based on gender, location and appearance of the neoplasm. Metastatic disease, presence of aggressive radiological features and low percentage of tumoral necrosis after neoadjuvant chemotherapy were associated with poor prognosis.

Telengiectatic osteosarcoma of mandible with special emphasis on immunohistochemical and molecular characteristics: A case report with review of literature

AbstractBackgroundTelangiectatic osteosarcoma (TOS) is an uncommon pathology accounting for about 0.4%–12% of all osteosarcomas with predilection for younger adults. It is most frequently seen in the metaphysis of long bones, appearing as painful osteolytic mass that histopathologically characterized by dilated, blood‐filled vascular spaces lined by malignant osteoblasts along with osteoid formation. It has exchangeable clinical, radiological and pathological features with benign lesions like aneurysmal bone cyst and giant cell tumour of bone as well. Thus, delineating this malignancy from its benign counterparts is a crucial part in the therapeutic management.AimTo report a case of telengiectatic osteosarcoma of jaw in a 17 year old female patient with special highlights on molecular diagnostics and therapeutic modules.Materials and MethodsA panel of immunohistochemical markers comprising of SATB2, CDK4, MDM2, panCK, CD31, desmin, NKX2.2 and TLE1 were employed in combination with fluorescent in‐situ hybridization to detect the prevalence of rearrangement in CDK4 and MDM2 genes.ResultsOn immunohistochemistry, the neoplastic cells were strongly positive for SATB2 and negative for CDK4, MDM2, panCK, CD31, desmin, NKX2.2 and TLE1. Fluorescent in‐situ hybridization of CDK4 and MDM2 genes was also negative.ConclusionConsidering its rarity in jaws combined with clinicopathological overlap with other benign pathologies, diagnosis of this entity is crucial in treatment planning and prognostic significance. Moreover, only five cases of TOS have been reported so far in the craniofacial region. Here, we have reported the sixth case of its kind with detailed clarification pertaining to its immunohistochemical and molecular aspects.

THU452 Polyostotic Fibrous Dysplasia Complicated By Aneurysmal Bone Cyst In A Patient With McCune-Albright Syndrome

Abstract Disclosure: E. Milazzo: None. K.L. Hermayer: None. Introduction: McCune-Albright Syndrome (MAS) is a rare mosaic disorder with GNAS mutations, encoding the alpha-subunit of the Gs G-coupled protein receptor, activating it, and inappropriately producing cAMP. The hyperfunctioning endocrinopathies associated with MAS are due to signaling through the TSH, LH, FSH, GHRH, and ACTH receptors. MAS clinical presentation occurs with café-au-lait skin macules, precocious puberty, and fibrous dysplasia (FD) of the bone. FD is a benign tumor that leads to increased rates of bone fractures and if it causes facial deformities, can be complicated with orbital neuropathies. An aneurysmal bone cyst (ABC) is a blood-filled cyst that can be a primary or secondary lesion due to co-existing lesions. ABC is a rare complication of FD. We report a rare case of ABC in a MAS patient who presented with acute visual disturbance and enlargement of the forehead and was successfully treated with surgery. Clinical Case: A 20-year-old female diagnosed with MAS at the age of 2 who had precocious puberty by the 3rd year of life and developed polyostotic FD in the right arm, left femur, cranial, and skull bones with multiple long bone fractures by the age of 5-6 and required numerous orthopedic surgeries. She presented with the characteristic café-au-lait skin macules on the back and right arm. In 2018, a slow decline of left eye vision required left cranial decompression of the optic nerve, with pathology showing fibrous tissue compatible with FD. In 2021, she complained of acute right forehead enlargement, compressing her right eye with blurry vision. An MRI showed FD involving the facial and skull bones with a new expansible lesion in the right frontal bone with internal layering fluid, exerting a mild mass effect on the frontal lobe and extending superiorly to the orbit with inferior displacement of the globe. These findings were consistent with an ABC. Right frontal craniectomy and cranioplasty were performed in 12/2021, with pathology showing a fibrous pseudocyst wall with associated lymphoplasmacytic inflammation and evidence of prior hemorrhage with Ki-67 in the cyst wall at 15%. Lab work showed chronic alkaline phosphatase elevation at 567IU/L (42-106IU/L), normal calcium at 9.2mg/dl (8.4-10.3mg/dl), phosphate at 3.3mg/dl (3.3-5.1mg/dl), and PTH at 26pg/ml (15-65mg/dl), with Vitamin D insufficiency at 25.1ng/ml (30-100ng/ml). Endocrinology workup was negative for thyroid, adrenal, gonadotrophic, and GH dysfunction. 5 months post-surgery, the patient demonstrated complete recovery, and MRI showed no recurrence of the ABC. Conclusion: ABC is a benign solitary tumor generally arising from the metaphysis of long bones and rarely involves the cranium. ABC associated with FD has only been reported in a few cases. The treatment is surgical excision, with radiation and cryotherapy used in nonorbital cases. Presentation: Thursday, June 15, 2023

Diagnóstico inicial del osteosarcoma y sarcoma de Ewing en la edad pediátrica

IntroductionOsteosarcoma and Ewing sarcoma are the most frequent malignant bone tumours in children. The aim of this study is to characterize clinical and radiological features at presentation of a large cohort of children with these diseases, radiological findings useful to differentiate them and the main prognostic factors. Material and methodsRetrospective analysis of clinical and imaging findings of 83 children diagnosed and treated of Ewing sarcoma and osteosarcoma in a paediatric hospital during a period of 10years. ResultsBoth tumours showed aggressive radiological features such as permeative or moth-eaten margins, cortical disruption, discontinuous periosteal reaction, intense contrast uptake, tumoral necrosis and soft-tissue component. They differed in their location, osseous matrix and gender predilection. Osteosarcoma occurred more frequently in the metaphysis of long bones (62%) with a blastic appearance (53%). Ewing sarcoma showed a predilection for male patients (71%), occurred in flat bones (42%) and in the diaphysis of long bones (58%) with a lytic appearance (82%). 29% of children presented with metastases at diagnosis, most frequently located in the lungs. Survival rates were 78% in osteosarcoma and 76% in Ewing sarcoma. Metastatic disease, aggressive radiological features and low percentage of tumoral necrosis after neoadjuvant chemotherapy were associated with poor prognosis (P<.05). ConclusionsImaging can confidently diagnose malignant paediatric bone tumours in children and may differentiate Ewing sarcoma from osteosarcoma, based on gender, location and appearance of the neoplasm. Metastatic disease, presence of aggressive radiological features and low percentage of tumoral necrosis after neoadjuvant chemotherapy were associated with poor prognosis.

Nonossifying Fibroma Involving Epiphysis of Long Bone-Case Report and Review of the Literature.

Nonossifying fibroma (NOF) is a common benign bone neoplasm and is usually observed in the first 2 decades of life. Most NOFs occur in the metaphysis of long bones of the lower extremities and migrate toward the diaphysis during skeletal maturation. Epiphyseal involvement by NOF has been rarely reported, with only one case found in the English literature. The authors report the second case of NOF involving the epiphysis of a long bone, the proximal tibia of a 21-year-old woman. Clinicians and pathologists should be aware of the rare possibility of epiphyseal involvement of long bones by this condition. Pathologists should select appropriate immunohistochemistry markers to rule out alternative diagnoses.