Nonossifying fibroma: characteristics at MR imaging with pathologic correlation

Update of pediatric bone tumors: osteogenic tumors and osteoclastic giant cell-rich tumors

There are numerous bone tumors in the pediatric population, with imaging playing an essential role in diagnosis and management. Our understanding of certain bone tumors has rapidly evolved over the past decade with advancements in next-generation genetic sequencing techniques. This increased level of understanding has altered the nomenclature, management approach, and prognosis of certain lesions. We provide a detailed update of bone tumors that occur in the pediatric population with emphasis on the recently released nomenclature provided in the 5^th edition of the World Health Organization Classification of Soft Tissue and Bone Tumours.

Edema-like marrow signal intensity (ELMSI) associated with nonossifying fibroma (NOF) on MRI: an uncommon finding in a common bone lesion

OBJECTIVE

To investigate the association between nonossifying fibroma (NOF) and perilesional edema-like marrow signal intensity (ELMSI) on MRI and discuss the clinical and diagnostic implications of this finding.

MATERIALS AND METHODS

A retrospective search for "nonossifying fibroma" and "NOF" on knee MRI reports of patients up to 20 years of age over a 5-year period was performed. A total of 77 patients (34 males, 43 females, ages 11-20) were identified, and each MRI was reviewed to evaluate for ELMSI associated with the NOF. Statistical analysis was performed to determine if there was a correlation with the presence of perilesional ELMSI and age, gender, lesion size, or signal characteristics.

RESULTS

Twelve patients out of 77 (16%) had ELMSI associated with a NOF. Excluding patients who had additional findings of pathologic fracture (n = 2), a known potential complication of NOFs, and edema related to an adjacent osteoid osteoma (n = 1), a total of 9 patients (12%) had otherwise unexplained perilesional ELMSI. There was no statistically significant difference between patients with vs. without perilesional ELMSI with respect to age (p = 0.08), gender (p = 0.28), lesion size (p = 0.52), or appearance on fluid-sensitive sequences (p = 0.81).

CONCLUSION

ELMSI can be seen about NOFs encountered around the knee joint on MRI, which may represent active healing and/or involutional change of this "do not touch" lesion in cases where no other explanation is identified.

Update of pediatric bone tumors-other mesenchymal tumors of bone, hematopoietic neoplasms of bone, and WHO classification of undifferentiated small round cell sarcomas of bone

There are numerous bone tumors in the pediatric population, with imaging playing an essential role in diagnosis and management. Our understanding of certain bone tumors has rapidly evolved over the past decade with advancements in next-generation genetic sequencing techniques. This increased level of understanding has altered the nomenclature, management approach, and prognosis of certain lesions. We provide a detailed update of bone tumors that occur in the pediatric population with emphasis on the recently released nomenclature provided in the 5th edition of the World Health Organization Classification of Soft Tissue and Bone Tumours. We discuss other mesenchymal tumors of bone, hematopoietic neoplasms of bone, and WHO classification of undifferentiated small round cell sarcomas of bone. We have detailed osteogenic tumors and osteoclastic giant cell-rich tumors, as well as notochordal tumors, chondrogenic tumors, and vascular tumors of the bone in separate manuscripts.

Comparison of MRI Findings among Osteofibrous Dysplasia, Fibrous Dysplasia, and NonOssifying Fibroma of the Long Bone

Background The characteristics of magnetic resonance imaging (MRI) findings among osteofibrous dysplasia (OFD), fibrous dysplasia (FD), and nonossifying fibroma (NOF) have yet to be determined.

Aims This study determines the differences of MRI features among OFD, FD, and NOF of the long bone.

Patients and Methods This study included 39 patients including 10 OFD, 13 with FD, and 16 with NOF of the long bone. All patients underwent preoperative MRI and histological examination. We retrospectively reviewed the MRIs and compared the imaging findings among the three pathologies.

Results The maximum diameter was significantly different among OFD (47.0 ± 18.6 mm), FD (59.0 ± 35.0 mm), and NOF (33.3 ± 15.0 mm) (p < 0.05). Multiplicity (60%, p < 0.01), eccentric distribution (100%, p < 0.05), septation (70%, p < 0.01), homogeneous intensity on T2-weighted images (70%, p < 0.01), homogeneous contrast enhancement (63%, p < 0.05), and intense contrast enhancement (88%, p < 0.01) were significantly more frequent in OFD. Centric distribution (69%, p < 0.01), cyst formation (54%, p < 0.01), and fluid-fluid level formation (31%, p < 0.01) were significantly more frequent in FD. Eccentric distribution (100%, p < 0.01), heterogeneous on T2-weighted images (100%, p < 0.01), predominant hypointensity on T2-weighted images (44%, p < 0.01), and the presence of intralesional hypointensity on T2-weighted images (88%, p < 0.01) were significantly more frequent in NOF.

Conclusion MRI features could differentiate OFD, FD, and NOF of the long bone.

CLINICAL FEATURES OF CONNECTIVE TISSUE DYSPLASIA, OSGOOD-SCHLATTER DISEASE AND MULTIPLE CORTICAL DISORDERS IN A CHILD

OBJECTIVE

The aim: To analyze scientific data on the problems of disorders of bone morphogenesis in children, in particular, non-ossifying fibroma. To analyze modern methods of diagnosis and treatment of this disease in the context of the latest scientific achievements.

PATIENTS AND METHODS

Materials and methods: The latest data of scientists from the world's leading clinics describing various forms of fibrous skeletal lesions in children of differ¬ent ages were analyzed. We examined a boy with fibrous lesions of the cortical layer of the knee joint bones and a girl with a large fibrous focus of the distal femoral metaphysis, which resulted in a closed pathological bone fracture. Surgical treatment, osteosynthesis, marginal resection of the tumor, bone grafting and histological examination were conducted.

CONCLUSION

Conclusions: Despite numerous studies of this disease, the etiopathogenesis of this disease has not been studied. There are no early symptoms of fibrous bone lesions in children. Diagnosis is possible only when a pathological fracture of the affected bone occurs due to extensive growth of fibrous tissue and a significant decrease in the mechanical strength of the bone. Most cases of recognition of such a disease occur accidentally when performing X-ray examinations for other reasons - bruises, sprains, arthralgias, osteochondropathy, infectious diseases, etc. It is known that boys are more mobile and require more frequent X-ray examinations for limb injuries than girls, so the likelihood of accidental detection of such changes increases significantly. Thus, long-term observations of children with fibrous bone lesions have shown that after 40 years, patients rarely developed malignant tumors - osteogenic sarcoma, fibrosarcoma, malignant fibroma of tubular bones, pelvic bones. There are no early symptoms of fibrous bone lesions in children. Recognition of such a disease occurs by chance when X-ray examinations are performed for other reasons.

Nonossifying Fibroma of the Distal Tibia: Predictors of Fracture and Management Algorithm

BACKGROUND

Nonossifying fibroma (NOF) is a common benign lesion in children and adolescents. This study investigated the risk of pathologic fracture in NOF lesions of the distal tibial based on anatomic location, clinical symptomatology, and imaging features, in order to propose an algorithm for the management of such lesions.

METHODS

In an IRB-approved retrospective case-control study, all patients diagnosed with NOF between 2010 and 2017 were extracted from our database. Patients below 18 years of age at the time of diagnosis and with lesions involving the distal tibia were included. Demographic data, the reason for visit, and the mechanism of injury were recorded. Radiographs were reviewed to record the size (absolute and relative to bone width) and location of each lesion. Computed tomography and magnetic resonance imaging examinations were also reviewed when available. Two authors graded all lesions using the Ritschl classification and determined the presence of 2 novel signs: the syndesmosis sign and the Pac-Man sign.

RESULTS

A total of 84 patients were included in the final analysis, of which 25 were in the fracture group and 59 in the nonfracture group. None of the patients in the fracture group was previously diagnosed with NOF, but nine (36%) patients had symptoms for >6 months preceding the fracture. Ankle sprain was the most common reason for visit in the nonfracture group. The lateral location of the lesion in the distal tibia (P=0.001), size (P<0.001 for both absolute and relative values), Ritschl stage (P=0.003), syndesmosis sign (P=0.005), and the Pac-Man sign (P=0.002) were significant predictors of fracture. All measurements had almost-perfect to perfect inter-rater agreements.

CONCLUSIONS

The most significant imaging risk factors for fracture are a larger size, Ritschl stage B, and the presence of cortical thinning on anteroposterior or lateral radiographs. We introduced 2 signs for these distal tibial NOFs, a scoring system, and a management algorithm that is based on radiographs alone but incorporates advanced imaging findings in equivocal cases.

LEVEL OF EVIDENCE

Therapeutic Level III-case-control study.

Usefulness of MR imaging for odontogenic tumors

MRI has become an invaluable diagnostic tool in all areas of the body. However, it has not been widely used to image odontogenic tumors of the jaw. Major advantages of MRI include excellent soft tissue contrast in the absence of ionizing radiation. Furthermore, diffusion-weighted MRI and dynamic contrast-enhanced MRI can be used as functional imaging techniques for assessing tissue biology. In this review article, we present representative MR images of several types of odontogenic tumors, and discuss MR imaging characteristics useful for differential diagnosis.

68Ga DOTA-TOC Uptake in Non-ossifying Fibroma: a Case Report

Non-ossifying fibroma (NOF) is a common benign bone tumor with a high probability of occurrence in children and adolescents. It is commonly seen in the metaphysis of long bones, eccentrically located, and can coexist with other malignant tumors such as neuroendocrine tumors (NET). To date, plain radiographs play a major role in the diagnosis of these benign bone tumors. Herein, we report the case of a 13-year-old male patient who was diagnosed with pulmonary NET and underwent right lung lobectomy for a hilar mass which later revealed a well-differentiated NET. The follow-up ⁶⁸Ga DOTA-TOC PET/CT showed a focal somatostatin receptor expression in the left distal femur, with corresponding CT component findings of a well-defined osteolytic bone lesion located within the medial aspect of the left distal femoral metaphysis, strongly indicative of NOF. To the best of our knowledge, this is the first reported case of such an occurrence.

Peering beneath the surface: Juxtacortical tumors of bone (part I)

Juxtacortical or surface tumors of bone are neoplasms arising from or just outside the cortex, and are composed of different histologic types. Although the imaging appearances of these lesions have similarities to their intramedullary counterparts, their location alters their radiographic and MR characteristics, creating difficulties in diagnosis. Meanwhile, several non-neoplastic lesions, such as stress reaction/stress fracture and indolent infectious processes, compound the differential diagnosis. Neoplastic juxtacortical lesions of bone have been classified into five categories: cartilaginous, fibrous, lipomatous, osseous, and metastatic tumors. Our goal in part one of this review is to illustrate the characteristic radiographic, CT and MR imaging features of various juxtacortical neoplasms, including pathognomonic imaging findings that can aid in diagnosis, and to develop an appropriate differential diagnosis for surface lesions based on imaging characteristics, lesion location and patient age.

Surgical treatment for symptomatic non-ossifying fibromas of the lower extremity with calcium sulfate grafts in skeletally immature patients

BACKGROUND

Non-ossifying fibromas (NOFs) are common benign bone lesions found in children and adolescents. They usually involve metaphysis of long bones, tend to gradually disappear with age and usually do not require surgery, while they are not associated with pathological fractures. The aim of this study was to evaluate the outcome and efficacy of a single-stage procedure, comprising curettage of the lesion and calcium sulfate pellet (CaSP) grafting, in skeletally immature patients with large, symptomatic NOF of the lower extremity, and the possible limitations of the procedure.

METHODS

Nine skeletally immature patients with symptomatic NOF of the lower extremity were treated between 2013 and 2016. Details of age, history of presentation, location and size (in mm) of the lesion, histology and follow-up details were recorded. Lesions were classified in Ritschl radio-morphological stages. CaSP integration was assessed by Irwing's classification. The average size of lesions was 54.6 mm in length (range 31-95). All lesions were symptomatic. The average bone expansion in relation to the bone diameter was 67.4% in the transversal plane (range 31-100) and 77.8% in the sagittal plane (range 55-100). Mean patient age at time of treatment was 9.8 years (range 7-14); mean follow-up was 2 years (range 2-4). All the patients were symptomatic, and 8 out of 9 (89%) NOFs were Ritschl type B. All the patients were treated surgically with a single-step approach, as described.

RESULTS

On average, 86 mL of CaSPs was used per case (range 10-250). None of the patients required internal fixation. At last follow-up visit, CaSPs were fully incorporated in all the patients according to Irwing's classification (Stage 3). No serous drainage from wounds was recorded in any of the patients. No cases of pathological fracture, bone deformity, growth arrest or growth disturbance or infection were observed. At last follow-up visit, all the patients had resumed full sport and daily life activities.

CONCLUSIONS

CaSPs offer a safe, cheap, convenient alternative to the autograft as an implant substitute that helps regeneration of bone in the defects produced by curettage of large, symptomatic NOFs. Chemical cauterization of bone walls does not interfere with CaSP integration into bone tissue.

Benign Bone Conditions That May Be FDG-avid and Mimic Malignancy

Positron emission tomography with the radiotracer ¹⁸F-fluoro-2-deoxy-d-glucose (FDG) plays an important role in the evaluation of bone pathology. However, FDG is not a cancer-specific agent, and knowledge of the differential diagnosis of benign FDG-avid bone alterations that may resemble malignancy is important for correct patient management, including the avoidance of unnecessary additional invasive tests such as bone biopsy. This review summarizes and illustrates the spectrum of benign bone conditions that may be FDG-avid and mimic malignancy, including osteomyelitis, bone lesions due to benign systemic diseases (Brown tumor, Erdheim-Chester disease, Gaucher disease, gout and other types of arthritis, Langerhans cell histiocytosis, and sarcoidosis), benign primary bone lesions (bone cysts, chondroblastoma, chondromyxoid fibroma, desmoplastic fibroma, enchondroma, giant cell tumor and granuloma, hemangioma, nonossifying fibroma, and osteoid osteoma and osteoblastoma), and a group of miscellaneous benign bone conditions (post bone marrow biopsy or harvest status, bone marrow hyperplasia, fibrous dysplasia, fractures, osteonecrosis, Paget disease of bone, particle disease, and Schmorl nodes). Several ancillary clinical and imaging findings may be helpful in discriminating benign from malignant FDG-avid bone lesions. However, this distinction is sometimes difficult or even impossible, and tissue acquisition will be required to establish the final diagnosis.

Nonossifying fibroma: A possible pitfall in F18-FD-PET/CT imaging of Hodgkin's disease

A 14-year-old girl was examined for a right lateral neck swelling and radiographic mediastinal widening. Biopsy of a right supraclavicular lymph node demonstrated the nodular sclerosing form of Hodgkin's lymphoma. An 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (F18-FDG-PET/CT) study showed several pathological areas of lymph-node uptake in the upper mediastum and right distal tibia. Radiography of the tibia revealed a nonossifying fibroma in the site corresponding to the distal tibial uptake. The PET appearance of benign fibro-osseous lesions may be similar to those of skeletal metastases. Information obtained by the CT component of the PET/CT study and by conventional radiography can be useful in preventing erroneous interpretations of F18-FDG-PET uptake.

Pitfalls in the diagnosis of common benign bone tumours in children

Benign bone tumours in children are frequent lesions, often with a typical and very identifiable radiological presentation. However, their natural evolution and complications may be the source of variations and errors in interpretation. It is therefore important to understand the possible sources of change in the radiological aspect and to be familiar with common pseudotumoral lesions. The main aim of this review is to review typical aspects of the most common benign bone tumours in children, as well as less frequent variants of these tumours.

Teaching points

• Benign bone tumours in children may have atypical radiological presentations.

• Some normal variants are commonly misinterpreted as tumours.

• X-ray is the main imaging tool for focal bone lesions.

• Depending on the X-ray, complementary imaging examinations and biopsy may be necessary.

MR findings of the osteofibrous dysplasia

OBJECTIVE

The aim of this study was to describe MR findings of osteofibrous dysplasia.

MATERIALS AND METHODS

MR images of 24 pathologically proven osteofibrous dysplasia cases were retrospectively analyzed for a signal intensity of the lesion, presence of intralesional fat signal, internal hypointense band, multilocular appearance, cortical expansion, intramedullary extension, cystic area, cortical breakage and extraosseous extension, abnormal signal from the adjacent bone marrow and soft tissue and patterns of contrast enhancement.

RESULTS

All cases of osteofibrous dysplasia exhibited intermediate signal intensity on T1-weighted images. On T2-weighted images, 20 and 4 cases exhibited heterogeneously intermediate and high signal intensity, respectively. Intralesional fat was identified in 12% of the cases. Internal low-signal bands and multilocular appearance were observed in 91%. Cortical expansion was present in 58%. Intramedullary extension was present in all cases, and an entire intramedullary replacement was observed in 33%. Cortical breakage (n = 3) and extraosseous mass formation (n = 1) were observed in cases with pathologic fractures only. A cystic area was observed in one case. Among 21 cases without a pathologic fracture, abnormal signal intensity in the surrounding bone marrow and adjacent soft tissue was observed in 43% and 48%, respectively. All cases exhibited diffuse contrast enhancement.

CONCLUSION

Osteofibrous dysplasia exhibited diverse imaging features ranging from lesions confined to the cortex to more aggressive lesions with complete intramedullary involvement or perilesional marrow edema.

Benign bone tumors

Benign bone lesions are a broad category that demonstrates a spectrum of activities from latent to aggressive. Differentiating the various tumors is important in order to properly determine necessary intervention. This chapter focuses on the presentation, imaging, diagnostic features, and treatment of the most common benign bone tumors in order to help guide diagnosis and management.

MRI of pediatric patients: Part 2, normal variants and abnormalities of the knee

OBJECTIVE

The purpose of this article is to discuss MRI of the pediatric knee and familiarize the reader with conditions encountered in the pediatric population. Clinical scenarios are included to convey important concepts and to orient the learner to normal variants and abnormalities of the pediatric knee. The conditions discussed include, but are not limited to, distal femoral metaphysial irregularity, isolated popliteus tendon avulsion, juvenile idiopathic arthritis, and discoid meniscus.

CONCLUSION

The knee is the joint that is most commonly imaged by MRI in children. Injury patterns and signs of other pathologic processes seen in skeletally immature patients are different from those seen in adults. Interpreting pediatric knee MRI studies may be a challenge for those unfamiliar with the evolving patterns of normal development and of the signs of conditions that are more prevalent in children. Through case scenarios, this article describes and provides images that depict conditions commonly encountered in the pediatric knee. Most of the described normal findings and abnormalities are more prevalent in the pediatric population than in adults, and a few of the conditions are, in fact, unique to pediatric patients.

Benign bone tumors

A solid knowledge of underlying histopathology of benign bone tumors aids in differential diagnoses of these tumors. Important factors in diagnosis of a bone tumor include patient age and gender; the bone involved; the location of the tumor along, within, or on the bone; lesion margin; matrix proliferation; and periosteal reaction. This article provides a review of the origin of the tumor matrix and its influence on the imaging properties of these tumors.

MRI of chondromyxoid fibroma

BACKGROUND

Chondromyxoid fibroma is a rare benign primary bone tumor of cartilage. Despite a characteristic radiographic appearance, chondromyxoid fibroma with atypical radiographic findings may mimic more common tumors.

PURPOSE

To describe the MR findings of chondromyxoid fibroma.

MATERIAL AND METHODS

MR images of 19 histopathologically confirmed chondromyxoid fibromas were retrospectively analyzed for signal intensity, periosteal reaction, adjacent abnormal bone marrow and soft tissue signal, and patterns of contrast enhancement.

RESULTS

All cases of chondromyxoid fibroma showed hypointense to intermediate signal intensity and internal hyperintense foci were observed in seven (37%) cases on T1-weighted images. On T2-weighted images, all lesions were hyperintense: peripheral intermediate signal band with central hyperintense signal in 11 (58%) of 19 lesions, whereas diffusely hyperintense with heterogeneous pattern in eight (42%). Periosteal reaction was observed in 11 (58%) of 19 cases. Adjacent abnormal bone marrow or soft tissue signal was observed in 12 (63%) or 14 (74%) of 19 cases, respectively. On contrast-enhanced T1-weighted images, peripheral nodular enhancement was observed in 69% (11/16) and diffuse contrast enhancement was observed in 31% (5/16) with homogeneous (n = 3) or heterogeneous (n = 2) patterns. Among the cases with peripheral nodular enhancement, the peripheral nodular enhancing portion generally corresponded to the peripheral intermediate signal band on T2-weighted images, although the peripheral enhancement was not as wide as a band of intermediate signal intensity. On the other hand, the central non-enhancing portion generally corresponded to the central hyperintense signal intensity on T2-weighted images.

CONCLUSION

The helpful features of chondromyxoid fibroma are the peripheral intermediate signal band and central hyperintense signal on T2-weighted images, generally corresponding to the peripheral nodular enhancement and central non-enhancing portion on contrast-enhanced T1-weighted images, respectively.

Musculoskeletal mnemonics: differentiating features

Mnemonics are often used in musculoskeletal radiology to help radiologists remember long differential diagnoses. However, unless the specific appearance of each entity on a differential is also recalled, mnemonics become useless. This article presents 8 mnemonics with their corresponding differential diagnoses and distinguishing features. Bubbly lucent lesions of bone are recalled with the FEGNOMASHIC mnemonic, but when only lucent lesions of the diaphysis are included, a more appropriate mnemonic is FEMALE. The lucent lesions of bone differentials often can be narrowed based on specific characteristics of the lesion but radiographic findings elsewhere and clinical information often help. Osseous metastases may present as lucent or sclerotic lesions; when sclerotic, the differential is best remembered with the mnemonic 5 "BEES" Like Pollen. The mnemonic for Wormian bones is PORKCHOPS. The Wormian bones in most of these entities are indistinguishable, so one must rely on radiographic findings outside the skull for diagnosis. By contrast, differentiating causes of acro-osteolysis is often possible with findings seen only on the hand radiographs; the mnemonic for acro-osteolysis is RADSHIP. In skeletally immature patients with frayed metaphyses, the mnemonic is CHARMS. Although the appearance of the fraying is seldom diagnostic, findings in the adjacent portions of the long bones may be characteristic. FETISH is the mnemonic used to remember the entities for the differential diagnosis of vertebra plana. Age of the patient, clinical history, and findings in the adjacent spine often help to provide the specific diagnosis. Nearly all the entities on the differential diagnosis for distal clavicle erosion (mnemonic: SHIRT Pocket) are included in other differentials in this article.

MRI of the knee: key points in the pediatric population

The knee is the joint which is most commonly imaged by MRI in children. With increasing participation in competitive sports at younger ages, knee injuries are common in children. While older adolescents have patterns of injury similar to those seen in adults, injuries seen in skeletally immature patients differ. In this essay, the MR findings of injuries of the skeletally immature knee are highlighted.

Cortical desmoid and the four clinical scenarios

We reviewed four patients diagnosed with a cortical desmoid lesion at the distal posterior medial femur. Each case reflects a clinical scenario that can be present. Cortical desmoid is a benign, self-limited entity which occasionally can exhibit aggressive radiologic features. Here, we present the specific imaging features in association with patients history and clinical findings facilitating establishment of correct diagnosis. Exact diagnosis is important in order to avoid unnecessary biopsy and complicated therapeutic strategies.

Non-ossifying fibroma, fibrous cortical defect and Jaffe-Campanacci syndrome: a biologic and clinical review

Non-ossifying fibroma of bone (NOF) is a common entity, more frequently found in male children and consisting of a solitary eccentric, lytic expanded lesion in the metaphysis of a long bone. The disorder is benign and most often asymptomatic but may result in a fracture requiring therapy. Of some importance is to distinguish NOF from another very similar but smaller lesion, fibrous cortical defect, which is almost always asymptomatic and eccentrically located. Even more striking is a very rarely encountered lesion known as Jaffe-Campanacci syndrome, which also occurs in children who present with typical non-ossifying fibromatous tumors but in multiple sites. In addition, these patients have some systemic and dermal findings resembling those seen in patients with Type 1 neurofibromatosis.

Nonossifying fibroma accompanied by pathological fracture in a 12-year-old runner

STUDY DESIGN

Resident's case problem.

BACKGROUND

Nonossifying fibroma (NOF) is the most common fibrous bone lesion in children. The lesion is usually asymptomatic, and rarely leads to pathological fractures.

DIAGNOSIS

We present the case of a 12-year-old boy who appeared to be normally developed but had a pathological insufficiency fracture associated with NOF in the distal femur. He was a member of a track athletics club and ran more than 5 km every day. Seven weeks prior to the initial evaluation he felt discomfort in the left distal thigh when running and felt pain upon knee flexion. The amount of discomfort increased gradually and he began to experience pain while running 4 weeks prior to his initial evaluation. At the time of the initial evaluation, he had tenderness over the distal thigh region and there was increased pain with weight bearing. Plain radiographs showed an irregular, well-defined cortical bone lesion, suggesting NOF, with vague increased density in the bone marrow across the femur and periosteal new bone, suggesting a fracture. Computed tomography confirmed a linear fracture with increased density across the femur leading to the cortical lesion. In the process of differential diagnosis osteosarcoma, or Ewing sarcoma, and bone/joint infection were ruled out using magnetic resonance imaging. The final diagnosis based upon the images and clinical course was pathological insufficiency fracture associated with NOF. The patient was treated with initial avoidance of weight bearing using 2 crutches for ambulation, followed by progressive weight bearing over a period of 5 weeks. Active range of motion of the knee joint was allowed. Three months after onset (5 weeks after the initial evaluation), the patient had normal gait without pain, whereupon the patient resumed his sport activities, beginning with jogging.

DISCUSSION

Although pathological fractures secondary to NOF in the femur are rare, NOF can cause pathological insufficiency fractures in athletes, even if the lesion is confined and small. The current case is a reminder of such a possibility. This case also provides a time course as a reference for the rehabilitation of patients in similar cases.

LEVEL OF EVIDENCE

Diagnosis, level 4.

MR imaging of the knee: incidental osseous lesions

The knee joint remains the articulation most frequently assessed by MR imaging, and osseous tumor and tumor-like lesions are not uncommon incidental imaging findings. This article reviews the most commonly encountered incidental lesions, emphasizing the characteristic MR imaging features. It is intended not as a complete review of the imaging findings associated with these lesions but as a summary, highlighting the MR imaging features that are most useful in suggesting a specific diagnosis. The authors organize incidental lesions into the following broad categories: cartilaginous, fibro-osseous, and degenerative. They do not address those lesions that are typically symptomatic and, as a result, likely to be directly related to the patients' clinical presentation and subsequent imaging.

Pitfalls in MR Image Interpretation Prompting Referrals to an Orthopedic Oncology Clinic

Patients referred to the authors' hospital for evaluation on suspicion of a bone or soft-tissue malignancy frequently present to the Orthopaedic Oncology Clinic with magnetic resonance (MR) images that show typical features of nonmalignant or nonneoplastic entities. The purpose of this article is to review the benign entities that may be mistaken by the radiologist for a malignancy and thus lead to needless referral to an orthopedic oncologist. Normal hematopoietic marrow and marrow edema due to a stress reaction may mimic a neoplasm at MR imaging, but knowledge of the typical patterns and locations of these features allows an accurate radiologic interpretation. The MR imaging appearance of osteonecrosis, Paget disease, benign bone lesions, and rheumatologic conditions may be confusing; in such circumstances, radiographic findings may help formulate a correct diagnosis. Knowledge of the common locations and appearances of bursae and ganglia is necessary so that radiologists do not misinterpret these benign entities as soft-tissue sarcomas. Soft-tissue trauma and inflammation also may mimic tumors at MR imaging, but a familiarity with the imaging patterns of nonneoplastic change in muscle allows the avoidance of misinterpretation. The clinical history, as always, is an important component of proper diagnosis. The radiologist can be especially useful to both the clinician and the patient by recognizing entities that are highly unlikely to represent malignancy and by confidently reporting those entities as benign, thereby sparing the patient an unnecessary trip to the orthopedic oncologist.

The role of MR imaging in the diagnostic characterisation of appendicular bone tumours and tumour-like conditions

MRI has an established role in the local staging of primary bone tumours. However, as the majority of tumours have non-specific appearances on MRI, the diagnosis is usually established on the basis of clinical history, plain film findings and biopsy. This article reviews the value of MRI in the further characterisation of appendicular bone tumours and tumour-like lesions, with particular reference to peri-lesional oedema, fluid-fluid levels, flow voids, fat signal, cartilage signal and dedifferentiation. These features are a useful adjunct for distinguishing between benign and malignant disease, pointing towards a more specific diagnosis, and guiding biopsy.

PET/CT characterization of fibroosseous defects in children: 18F-FDG uptake can mimic metastatic disease

OBJECTIVE

The purpose of this study was to characterize the anatomic appearance and metabolic activity of nonossifying fibromas, fibrous cortical defects, and cortical desmoids on PET/CT images.

CONCLUSION

Over a 14-month period, we identified eight nonossifying fibromas, four fibrous cortical defects, and two cortical desmoids in 330 children who underwent PET/CT for the evaluation of a known or suspected malignancy. CT, conventional radiography, MRI, or clinical follow-up was used to confirm the diagnoses of these fibroosseous lesions. Eleven of the 14 children underwent multiple PET/CT examinations; thus, 34 studies were included. The lesions showed variable metabolic activity as indicated by 18F-FDG uptake: 19 PET/CT examinations showed lesions with mild 18F-FDG uptake, eight showed moderate 18F-FDG uptake, and seven showed intense uptake. When PET reveals metabolically active osseous abnormalities in children who are at risk for bone metastases, benign fibroosseous lesions should be considered in the differential diagnosis before additional diagnostic procedures are undertaken. Benign fibroosseous lesions may be metabolically active and thus mimic metastatic osseous disease in children with underlying malignancies. Correlative CT or other anatomic imaging can confirm the benign nature of these lesions.

Characterization of pediatric skeletal tumors and tumor-like conditions: specific cross-sectional imaging signs

The radiograph is indispensable for characterizing pediatric skeletal lesions. However, cross-sectional imaging with CT and MRI can provide additional information and augment or confirm an impression obtained from the initial radiographic findings. This review will highlight the role of CT and MRI in characterizing pediatric skeletal tumors and tumor-like conditions. Focus will be given to the contributions of each modality to the process of characterizing skeletal lesions, recalling that cross-sectional imaging is more commonly obtained for the purpose of determining extent of disease rather than for characterization.

Contour irregularities of the distal femur caused by developmental, traumatic, and benign cortically-based neoplastic conditions: radiographic and MRI correlation

This review illustrates the radiographic and magnetic resonance imaging (MRI) appearances of a variety of entities that result in surface contour abnormalities of the distal femur. Such abnormalities may result from developmental variants expressed in the growing skeleton, from trauma, or from cortically-based tumours. As the number of MRI examinations of the knee performed annually to exclude internal derangement increases, the frequency with which these variants and pathological entities are encountered will likewise increase. In most cases, the location of the lesion, as well as its specific imaging characteristics, will allow an accurate diagnosis.

Epiphyseal osteoblastoma of tibia with xanthomatous stromal reaction

Osteoblastoma occurring in long bones has a distinctive predilection for the metaphysis and the diaphysis. Epiphyseal location is rare. Although variation in histologic patterns is a well-known feature of this tumor, xanthomatous stromal reaction has not yet been described. We report a case of a 34-year-old man who developed an osteoblastoma primarily located in the epiphysis of his left tibia with extension into the metaphysis. The striking histologic features included a prominent xanthoma-like stroma consisting of foamy histiocytes in addition to focal areas with classical configuration of an osteoblastoma. The significance of this finding is discussed.

Metaphyseal fibrous defects

Nonossifying fibromas and fibrous cortical defects are the most common benign lesions of the skeletal system. They are frequently detected incidentally on radiographs taken for an unrelated reason. The diagnosis is routinely made solely on the basis of the history, physical examination, and radiographic appearance. The incidence of multifocal nonossifying fibroma is typically underestimated in patients initially found to have a solitary lesion; the use of a limited skeletal survey rather than bone scan may help detect multifocal lesions in this population. Small, asymptomatic lesions may be followed over time using serial radiographs. Incisional biopsy, curettage, and bone grafting are indicated for large lesions that raise concern for impending pathologic fracture, for lesions that have become painful, and for lesions whose characteristics prevent a definitive radiographic diagnosis. Pathologic fractures involving these lesions should be treated with cast immobilization until the fracture has healed, followed by biopsy, curettage, and bone grafting.

Malignant and benign bone tumors

The authors have intentionally included some confusing examples to demonstrate that the imaging findings of benign and malignant pediatric bone lesions are not always pathognomonic. The radiologist's role is to recognize malignant bone lesions and encourage the prompt referral of these patients to an appropriate institution for biopsy and treatment. The radiologist must also be able to identify benign lesions and help determine whether these lesions require biopsy and intervention or simply observation.

Imaging Guided Biopsy: An Alternative to Surgical Biopsy

Imaging guided percutaneous core needle biopsy of the breast is an accurate and cost-effective method for the diagnosis of indeterminate breast lesions. It is also useful for the preoperative confirmation of suspected carcinoma. Depending on the location of the lesion in the breast, its imaging characteristics, and the configuration of the breast, biopsy using sonographic or stereotactic guidance may be preferable. However, for many lesions either technique can be used. A variety of biopsy probes are available. For many lesions the ability to make a diagnosis does not appear to depend on the probe size or configuration. However, when calcifications undergo biopsy, the retrieval of larger volumes of tissue may improve the accuracy of the diagnosis of atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS), and other rare lesions. Major complications are rare with these techniques. With benign histologies, most patients can avoid surgery and return to 6-month follow-up or routine screening mammography. When benign histologies are not concordant with the imaging pattern, when certain high-risk lesions are found at core biopsy, and when the pathologist is unable to make a definitive diagnosis based on the small volume of tissue removed, surgical biopsy is necessary. However, the vast majority of patients with benign diagnoses can avoid surgery with these biopsy techniques. It should be remembered that these techniques are not appropriate for the treatment of breast carcinoma at the present time.

Cost-effectiveness of stereotactic 11-gauge directional vacuum-assisted breast biopsy

OBJECTIVE

The purpose of our study was to determine the frequency with which stereotactic 11-gauge directional vacuum-assisted breast biopsy obviated a surgical procedure and to calculate cost savings attributable to that biopsy method.

MATERIALS AND METHODS

We retrospectively reviewed 200 consecutive solitary nonpalpable lesions on which stereotactic 11-gauge directional vacuum-assisted breast biopsy was performed. Cost savings were calculated using Medicare reimbursements. Mammograms, histologic findings, and medical records were reviewed.

RESULTS

Stereotactic 11-gauge directional vacuum-assisted biopsy obviated a surgical procedure in 151 (76%) of 200 lesions, including 112 (73%) of 154 calcific lesions and 39 (85%) of 46 masses. Reasons for not obviating a surgical procedure in 49 lesions (25%) included recommendation for surgical biopsy in 35 lesions (18%), small carcinomas treated by excision in 10 lesions (5%), and histologic underestimation in four lesions (2%). Stereotactic 11-gauge directional vacuum-assisted biopsy decreased the cost of diagnosis by S264 per case, a 20% ($264/$1289) decrease in the cost of diagnosis compared with surgical biopsy. Of 200 lesions that had stereotactic 11-gauge directional vacuum-assisted biopsy, 106 (53%) would not have been amenable to 14-gauge automated core biopsy because of their small size, their superficial location, or inadequate breast thickness.

CONCLUSION

Stereotactic 11-gauge directional vacuum-assisted breast biopsy obviated a surgical procedure in 76% of lesions, yielding a 20% decrease in cost of diagnosis compared with surgical biopsy. Although savings per case are modest, 11-gauge directional vacuum-assisted biopsy expands the spectrum of lesions amenable to stereotactic biopsy, increasing cost savings in the population.