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Focal myositis is a pseudotumor of soft tissue that typically occurs in the deep soft tissue of the extremities, and is a relatively rare lesion. There is a wide clinical spectrum, with approximately one-third of patients with focal myositis subsequently developing polymyositis, and clinical symptoms of generalized weakness, fever, myalgia, and weight loss, with elevation of creatine phosphokinase. We report the case of a patient with focal myositis who subsequently developed myositis ossificans-like features.

Scintigraphy with technetium-99m methylene diphosphonate (MDP) delineates a wide spectrum of nonosseous disorders. Neoplastic, hormonal, inflammatory, ischemic, traumatic, excretory, and artifactual entities demonstrate abnormal soft-tissue uptake of Tc-99m MDP. Mechanisms leading to increased extraosseous Tc-99m MDP uptake include extracellular fluid expansion, enhanced regional vascularity and permeability, and elevated tissue calcium concentration. The composition of the calcium deposition and the presence of other metallic ions (eg, iron and magnesium) are important. Soft-tissue Tc-99m MDP uptake is seen in benign (tumoral calcinosis, myositis ossificans) and malignant (sarcomas, adenocarcinomas, metastases) neoplastic entities. Hormonal disturbances in calcium metabolism, especially in hyperparathyroidism, can lead to metastatic calcification, visualized with Tc-99m MDP scintigraphy. Tissue damage from inflammation, infection, or physical trauma results in localized hyperemia, edema, or calcium (and hemosiderin) deposition based on their pathophysiologic characteristics. Urinary tract obstruction, anomalies, or dysfunction are demonstrated by Tc-99m MDP imaging. Common artifacts are related to faulty radiopharmaceutical preparation, Tc-99m MDP administration, and imaging technique. Recognition of these modes of extraskeletal Tc-99m MDP uptake can enhance the diagnostic value of bone scintigraphy.

Langerhans cell histiocytosis (LCH), previously called histiocytosis X, refers to a spectrum of disease characterized by idiopathic proliferation of histiocytes producing focal or systemic manifestations. Causes and pathogenesis remain unclear. However, recent studies suggest abnormal immune regulation as an important factor. The three classic syndromes may have considerable clinical overlap: eosinophilic granuloma, in which the disease is limited to bone in patients usually 5-15 years old; Hand-Schüller-Christian disease, characterized by multifocal bone lesions and extraskeletal involvement of the reticuloendothelial system (RES) usually seen in children 1-5 years old; and Letterer-Siwe disease, in which there is disseminated involvement of the RES with a fulminant clinical course in children less than 2 years old. Osseous involvement is typically in the flat bones, with lesions of the skull, pelvis, and ribs accounting for more than half of all lesions. About 30% of lesions are in long bones. Radiographic appearance of osseous LCH depends on site of involvement and phase of the disease. Early lesions appear aggressive with poorly defined margins and lamellated periosteal reaction. Late lesions appear well defined and may show sclerotic margins and expanded remodeled appearance.

Increasing use of MR to evaluate primary bone neoplasms has stimulated numerous articles on the initial assessment of these lesions. However, scant MR literature has been written about the postoperative MR appearance. We studied the MR appearance of lesions treated by curettage followed by packing with cancellous bone-chip allograft. We retrospectively reviewed the MR scans of 18 consecutive patients treated in this way. Pathologic diagnoses of these lesions were confirmed according to commonly accepted criteria. The allograft sites showed a distinctive pattern of speckled bright signal on T1-weighted images in eight cases. Thirteen of 18 grafts showed a whorled or speckled pattern of increased signal on the T2-weighted images. Only four allograft regions had predominantly low signal on both T1- and T2-weighted images. Two of 18 patients had recurrent tumor proved by open biopsy. MR images in these cases showed areas of homogeneous signal that replaced areas of speckled hyperintensity on both T1- and T2-weighted images. In both these recurrences the tumor had signal intensity similar to that seen on the preoperative MR study. We conclude that knowledge of the MR appearance of cancellous bone chip allografts is important to avoid misinterpreting areas of high signal on T1- or T2-weighted images as areas of recurrence of tumor and/or hemorrhage.

The radiologic features of giant cell tumor (GCT) and giant cell reparative granuloma (GCRG) of bone often strongly suggest the diagnosis and reflect their pathologic appearance. At radiography, GCT often demonstrates a metaepiphyseal location with extension to subchondral bone. GCRG has a similar appearance but most commonly affects the mandible, maxilla, hands, or feet. Computed tomography and magnetic resonance (MR) imaging are helpful in staging lesions, particularly in delineating soft-tissue extension. Cystic (secondary aneurysmal bone cyst) components are reported in 14% of GCTs. However, biopsy must be directed at the solid regions, which harbor diagnostic tissue. These solid components demonstrate low to intermediate signal intensity at T2-weighted MR imaging, a feature that can be helpful in diagnosis. Multiple GCTs, although rare, do occur and may be associated with Paget disease. Malignant GCT accounts for 5%-10% of all GCTs and is usually secondary to previous irradiation of benign GCT. Treatment of GCT usually consists of surgical resection. Recurrence is seen in 2%-25% of cases, and imaging is vital for early detection. Recognition of the spectrum of radiologic appearances of GCT and GCRG is important in allowing prospective diagnosis, guiding therapy, and facilitating early detection of recurrence.

Magnetic resonance (MR) imaging has emerged as the preferred modality for the imaging evaluation of musculoskeletal tumors. Although there is general agreement on the value of MR in diagnosis and staging, the use of intravenous contrast in the evaluation of musculoskeletal lesions remains controversial. The purpose of this review is to highlight these controversies, to put them in perspective, and to suggest recommendations for the use of gadopentetate dimeglumine. The following specific areas will be addressed: (a) evaluation of soft-tissue tumors, (b) diagnosis of low-grade chondrosarcoma and the use of contrast material in identification of intraosseous metastases, (c) monitoring response to chemotherapy, (d) evaluation for local recurrence after surgery and/or radiation therapy, and (e) selection of biopsy site.

The MR appearance of soft-tissue masses that simulate neoplasms has been described. In some cases, radiographs may demonstrate characteristic findings in association with MR imaging that may be diagnostic, such as an ossific rim seen in myositis ossificans, periosteal reaction seen in fibro-osseous pseudotumor, and retained foreign bodies present in a foreign body reaction or abscess. In other cases, the characteristic lesion location, age of the patient, and clinical presentation may be suggestive of the diagnosis, as in elastofibroma and nodular fasciitis.

Musculoskeletal tumors of the hand and wrist are relatively uncommon. Yet, despite their overall rarity, certain bone and soft-tissue lesions have a predilection for this location. This article reviews the common musculoskeletal tumors of the hand and wrist. It is not intended as a comprehensive review but as an overview, emphasizing the use of MR imaging in the evaluation of these lesions and highlighting those diagnoses that may be suggested by MR imaging.

To assess the effectiveness of gadopentetate dimeglumine in the magnetic resonance (MR) imaging evaluation of soft-tissue masses without osseous involvement, 30 patients underwent MR imaging before and after administration of contrast material (0.1 mmol/kg). Of the 30 lesions, 22 were benign and eight were malignant; histologic confirmation was available in all lesions except one benign lesion. Overall, enhancement was detected in 26 (87%) of 30 lesions: 18 (82%) of the 22 benign lesions and eight (100%) of eight malignant lesions. Enhancement was characterized as homogeneous (two [11%] benign lesions, two [25%] malignant lesions), inhomogeneous (11 [61%] benign lesions, six [75%] malignant lesions), or peripheral (five [28%] benign lesions, no malignant lesions). Of the 19 lesions assessed for a change in enhancement over time, seven (37%) showed an increase and two (11%) showed a decrease in signal intensity. The authors conclude that benign and malignant soft-tissue lesions could not be differentiated solely on the basis of enhancement (pattern, degree, or time course).

MR imaging is considered the procedure of choice for detecting and staging soft-tissue tumors. Its ability to show differences between benign and malignant soft-tissue tumors and its usefulness in suggesting a specific histologic diagnosis remain controversial. We studied the MR features of synovial sarcoma in 34 patients to determine if these tumors have specific MR findings that can be used to suggest the diagnosis.MR imaging studies of 34 patients with synovial sarcoma were collected from two institutions and studied to determine the following characteristics of the tumor: size, shape, location, signal intensity and homogeneity, margin definition, presence of hemorrhage, and relationships to adjacent structures. These findings were then correlated with pathologic findings.The tumors tended to be deep, large (85% wereor = 5 cm in diameter), and located in the extremities with epicenters close to joints (63% within 7 cm of a joint). The lesions were usually inhomogeneous on T2-weighted images (82%) and clearly delineated from surrounding tissues (91%). Forty-four percent had high signal consistent with hemorrhage on both T1- and T2-weighted images. Fluid-fluid levels, best visualized on T2-weighted images, were present in 18% of patients. Thirty-five percent of the lesions had areas that were hyper-, iso-, and hypointense relative to fat on T2-weighted images, constituting a triple signal intensity. The tumors frequently involved adjacent bone, with 71% invading, eroding, or touching bone. No association of pathologic subtypes with specific imaging findings was noted.Our results show a spectrum of MR imaging findings in synovial sarcoma. Nevertheless, the results suggest that synovial sarcoma should be considered when MR images show a relatively well-defined but inhomogeneous hemorrhagic lesion near a joint and in contact with bone. Fluid-fluid levels and areas hyper-, hypo-, and isointense relative to fat (triple signal) on T2-weighted sequences support the diagnosis.

In summary, MR imaging is the preferred modality for the evaluation of a soft tissue mass after plain films have been taken. The radiologic appearance of certain soft tissue tumors or tumorlike processes such as myositis ossificans, benign fatty tumors, intramuscular hemangiomas, pigmented villonodular synovitis, and certain hematomas may be sufficiently unique to allow a strong presumptive radiologic diagnosis. It must be emphasized that MR cannot reliably distinguish between benign and malignant lesions, and when radiologic evaluation is nonspecific, one is ill advised to suggest a lesion is benign or malignant solely on the basis of its MR appearance. CT may be useful in specific instances for the identification of subtle soft tissue mineralization in those patients in whom lesions are not adequately evaluated by radiographs. Ultrasonography may be useful in the assessing of recurrent disease as well as in establishing tumor vascularity.

Cartilaginous tumors can be subdivided into several categories according to the following three criteria: (1) Is the lesion benign or malignant? (2) Is the lesion a pure or impure cartilaginous tumor? (3) Is the epicenter of the lesion intraosseous, juxtacortical, or in the soft tissues? This article focuses on the four most common benign cartilaginous tumors, enchondroma, osteochondroma, chondroblastoma, and chondromyxoid fibroma, and on chondrosarcoma. It reviews the biologic and developmental considerations of each and discusses in depth the basic concepts in the radiologic diagnosis of cartilaginous tumors.

We describe the case of a 21-year-old woman with a synovial sarcoma of the thigh, who exhibited a soft-tissue metastasis to the shoulder approximately 3 months after her initial presentation. Due to its increasing availability and the recognized importance of MRI in the preoperative evaluation of patients with soft-tissue masses, it is important to be aware of even the uncommon manifestations of frequently encountered soft-tissue sarcomas.

We present a case of primary lymphoma of bone arising in the proximal tibial epiphysis of a 16-year-old boy. To the best of our knowledge, primary lymphoma of bone has not been described previously as a mimicker of chondroblastoma. This case report is intended to increase awareness among clinicians and radiologists that primary lymphoma of bone can present with a long clinical prodrome and initially benign radiographic appearance. Early recognition of this unusual presentation will (hopefully) increase the likelihood of cure. However, it is recognized that in children, primary lymphoma of bone is a rare diagnosis and associated with a poor prognosis unless aggressive treatment is utilized [8].

We report a case of a clinically and radiographically dominant osteosarcoma of the proximal end of the tibia, in which the second skeletal focus of osteosarcoma was apparent on MRI, after having escaped detection on routine radiographs and scintigraphy. Detection of the second lesion significantly altered the subsequent treatment and prognosis. The improved sensitivity of MRI may increase the accuracy of the diagnosis of osteosarcomatosis. Although further study is needed, MRI study of long bones, especially T1-weighted images in the coronal plane, may be considered as a screening procedure to exclude occult skeletal involvement in patients with osteosarcoma and negative standard metastatic evaluation.

Osteoid osteoma is a benign skeletal neoplasm composed of osteoid and woven bone that rarely exceeds 1.5 cm in greatest dimension. The lesion is most commonly located in the cortex of long bones where it is associated with dense, fusiform, reactive sclerosis. Less often, it may be cancellous, where reactive osteosclerosis is usually less intense and may be distant from the lesion. Cancellous lesions are frequently intraarticular (most often in the hip) and may be associated with synovitis and joint effusion. Rarely, osteoid osteomas occur in a subperiosteal location. Patients are usually young, and there is a strong male predominance. Pain is the most common symptom. Radiographs of patients with cortical osteoid osteoma are often diagnostic. Intraarticular lesions, however, may be subtle, and scintigraphy may be required to locate the lesion for subsequent computed tomography (CT). CT is useful to identify and precisely locate the lesion and to provide guidance for percutaneous localization or treatment.

The cause of adolescent idiopathic scoliosis remains an enigma. Several studies have demonstrated abnormalities of posture, proprioception, and equilibrium control in patients with adolescent idiopathic scoliosis. These functions are integrated by structures in and around the brain stem. Twenty-seven patients with adolescent idiopathic scoliosis were studied with magnetic resonance imaging to delineate the anatomy of the brain stem in such patients. Imaging was conducted from the hypothalamus to the spinal cord at C3 in 26 patients; the remaining patient underwent an incomplete study because of a claustrophobic reaction. The study group consisted of 25 females and 2 males with an average age of 16 + 5 years. There were 19 right thoracic curves, 5 thoracolumbar curves, and 3 left lumbar curves. The mean primary curve size was 27 degrees at the most recent clinical evaluation. Seven patients were treated with observation, 14 with bracing, and 6 with surgery. The magnetic resonance imaging studies were read independently by three attending radiologists in a randomized, blinded fashion along with the magnetic resonance imaging studies of 11 controls. Asymmetry in the ventral pons or medulla in the area of the corticospinal tracts was noted in seven study patients and one control; one study patient had an enlarged cisterna magna and one an inconclusive (incomplete) study. These findings may support previous studies that have suggested a central nervous system abnormality as a cause of adolescent idiopathic scoliosis.

We present a case of arthritis of the wrist in an elderly man due to Mycobacterium avium-intracellulare. Prior steroid injections and a surgical procedure on the affected wrist were predisposing risk factors for subsequent mycobacterial involvement of the skeleton. Radiographs demonstrated findings characteristic of tuberculous arthritis: particularly, osteopenia with marginal erosions and diffuse lytic lesions involving the carpals, proximal metacarpals, and distal ends of the radius and ulna. MR scans showed soft-tissue involvement and extensive marrow replacement consistent with infection. It is to be reemphasized that the clinical and radiological findings in this case are very often indistinguishable from TB. The diagnosis depends on the results of tissue culture. Since radiologists are likely to be involved increasingly in interpreting images of immunocompromised patients afflicted with a variety of both typical and atypical infections, it is important occasionally to report rare infections such as that described herein.

The case discussed is that of a 31-year-old woman with long-standing hypertrophy and vascular symptoms of the right lower extremity. The etiology of these abnormalities remained undiagnosed, although the patient was treated symptomatically. Following presentation, both MR images and contrast-enhanced CT scans were adequate for diagnosis of the underlying arteriovenous malformation. This was confirmed by arteriography, and the patient received palliative treatment by sequential intra-arterial embolization.

Ewing sarcoma is a relatively common, highly malignant bone tumor that typically occurs in adolescents and young adults aged 10-25 years. Our archives contain 328 cases of histologically proved and radiologically correlated Ewing sarcoma collected in consultation over 40 years. From this series, we identified 34 lesions (10%) arising in ribs. Radiographically, the affected rib was predominantly lytic in most (82%) cases, but mixed lytic-sclerotic (9%) and even predominantly sclerotic (9%) patterns were also encountered. The affected rib was "expanded" in 35% of cases, although the contour change was usually mild. Abnormalities of the affected ipsilateral hemithorax varied from subtle, isolated rib involvement to solitary rib involvement accompanied by complete opacification of the hemithorax. We describe the spectrum of radiologic findings of primary Ewing sarcoma of rib, augmented where appropriate by accompanying pathologic material.

Many different imaging modalities are available to assist in the evaluation of hip disease. One must choose the image or series of images that not only provide the most diagnostic and clinical information, but also remain the simplest and most cost effective for the patient. The initial examination should be the conventional radiograph. This will provide, in most instances, the most diagnostic information for arthritic disease, stress and insufficiency fractures, infection, and bone tumors. If the conventional radiograph is normal, or if more information is needed, bone scintigraphy should be done next. Bone scintigraphy will confirm the presence of disease, demonstrate its anatomic location, and give some information as to its physiologic state. Computed tomography does not play an important role in the evaluation of hip disease except in acute fractures involving the acetabulum. MR imaging is the modality of choice for diagnosing and staging osteonecrosis, searching for marrow disease, assessing cartilage abnormality, and evaluating the extent of soft-tissue disease.

Skeletal fibrous dysplasia is a developmental anomaly in which normal bone marrow is replaced by fibroosseous tissue. This process may be localized to a single bone, or even a small segment thereof, or affect the skeleton diffusely. The radiologic archives of the Armed Forces Institute of Pathology (AFIP) contain 501 cases of histologically proved and radiographically correlated fibrous dysplasia (of which 427 cases are monostotic and 74 cases are polyostotic). We present the spectrum of radiologic findings, including those from bone scintigraphy, computed tomography, and magnetic resonance imaging, augmented where appropriate by accompanying pathologic material.

A review of the 690 cases of osteosarcoma in the radiographic file of the Armed Forces Institute of Pathology revealed 29 cases of "osteosarcomatosis" (multiple skeletal sites of osteosarcoma). Fifteen of these patients were 18 years old and under and manifested rapidly appearing, usually symmetric, sclerotic metaphyseal lesions. The remaining 14 patients were more than 18 years old and had fewer, asymmetric sclerotic lesions. In most patients (28 of 29), a radiographically dominant skeletal tumor was seen. Pulmonary metastases occurred in the majority of patients and were detected at the same time as the bone lesions. These 29 patients were studied with regard to demographic data and skeletal distribution and radiographic appearance of their lesions. As a result of the findings, a metastatic origin from a primary dominant osteosarcoma is favored over a multifocal origin as the basis for osteosarcomatosis. Osteosarcomatosis is more commonly encountered in the mature skeleton than has been previously recognized.

Three patients with the unusual manifestation of atlantoaxial subluxation in Reiter's syndrome are studied. Each patient had mild symptoms referable to the cervical spine and radiologic evidence of erosive disease elsewhere in the skeleton. One patient had an 11-year history of Reiter's syndrome when the atlantoaxial subluxation was detected. The other two had atlantoaxial subluxation detected within 1 year of initial presentation, at variance with three other such patients that were reported previously, in whom there was a 6- to 10-year interval from initial presentation until radiographic documentation of atlantoaxial subluxation. Cervical spine radiographs, including flexion and extension views, are recommended for all patients with Reiter's syndrome and cervical spine symptoms.