From the archives of the AFIP: benign musculoskeletal lipomatous lesions

Benign lipomatous lesions involving soft tissue are common musculoskeletal masses that are classified into nine distinct diagnoses: lipoma, lipomatosis, lipomatosis of nerve, lipoblastoma or lipoblastomatosis, angiolipoma, myolipoma of soft tissue, chondroid lipoma, spindle cell lipoma and pleomorphic lipoma, and hibernoma. Soft-tissue lipoma accounts for almost 50% of all soft-tissue tumors. Radiologic evaluation is diagnostic in up to 71% of cases. These lesions are identical to subcutaneous fat on computed tomographic (CT) and magnetic resonance (MR) images and may contain thin septa. Lipomatosis represents a diffuse overgrowth of mature fat affecting either subcutaneous tissue, muscle or nerve, and imaging is needed to evaluate lesion extent. Lipoblastoma is a tumor of immature fat occurring in young children, and imaging features may reveal a mixture of fat and nonadipose tissue. Angiolipoma, myolipoma, and chondroid lipoma are rare lipomatous lesions that are infrequently imaged. Spindle cell and pleomorphic lipoma appear as a subcutaneous lipomatous mass in the posterior neck or shoulder, with frequent nonadipose components. Hibernoma appears as a lipomatous mass with serpentine vascular elements. Benign lipomatous lesions affecting bone, joint, or tendon sheath include intraosseous lipoma, parosteal lipoma, liposclerosing myxofibrous tumor, discrete lipoma of joint or tendon sheath, and lipoma arborescens. Intraosseous and parosteal lipoma have a pathognomonic CT or MR appearance, with fat in the marrow space or on the bone surface, respectively. Liposclerosing myxofibrous tumor is a rare intermixed histologic lesion commonly located in the medullary canal of the intertrochanteric femur. Benign lipomatous lesions may occur focally in a joint or tendon sheath or with diffuse villonodular proliferation in the synovium (lipoma arborescens) and are diagnosed based on location and identification of fat. Understanding the spectrum of appearances of the various benign musculoskeletal lipomatous lesions improves radiologic assessment and is vital for optimal patient management.

Eosinophilic Fasciitis: Spectrum of MRI Findings

OBJECTIVE

Our objective was to describe the spectrum of MRI features of eosinophilic fasciitis.

CONCLUSION

MRI findings in eosinophilic fasciitis are characteristic and consist of abnormal fascial signal intensity and enhancement, both of which are directly proportional to disease activity. MRI provides a useful aid for diagnosis and a marker for disease activity and response to treatment.

Imaging characteristics of cherubism

OBJECTIVE

We sought to describe the radiographic and imaging features of cherubism.

CONCLUSION

Cherubism is a rare osseous disorder of children and adolescents. Although the radiologic characteristics of cherubism are not pathognomonic, the diagnosis is strongly suggested by bilateral relatively symmetric jaw involvement that is limited to the maxilla and mandible. Imaging typically shows expansile remodeling of the involved bones, thinning of the cortexes, and multilocular radiolucencies with a coarse trabecular pattern.

Principles of bone and soft tissue imaging

Tumors involving the upper extremity are common. Although there are a wide variety of lesions that may occur in the hand and wrist, certain lesions have a predilection for this location. This article highlights the spectrum of imaging modalities available for the evaluation of upper extremity tumors, providing guidelines for optimum selection of radiologic examinations while emphasizing the fundamental principles inherent to tumor imaging.

Cysts, geodes, and erosions

Subchondral cystic lesions are common features that are associated with many arthropathies and synovial-based processes. Although not comprehensive in scope, this article correlated the pathophysiology and imaging features of several of these disorders to better understand the associated subchondral lucencies. The imaging features of these subchondral cystic lesions were described in each process, and, in some cases, demonstrated overlapping features. By becoming familiar with the disease processes and recognizing the imaging appearances and associated clinical findings, the radiologist will be better able to differentiate these benign entities from more aggressive processes, such as tumor. Subchondral cystic lesions are common features that are associated with many arthropathies and synovial-based processes. Although not comprehensive in scope, this article correlated the pathophysiology and imaging features of several of these disorders to better understand the associated subchondral lucencies. The imaging features of these subchondral cystic lesions were described in each process, and, in some cases, demonstrated overlapping features. By becoming familiar with the disease processes and recognizing the imaging appearances and associated clinical findings, the radiologist will be better able to differentiate these benign entities from more aggressive processes, such as tumor.

Osseous involvement in calcific tendinitis: a retrospective review of 50 cases

OBJECTIVE

The purpose of this study was to describe the spectrum of radiologic and pathologic manifestations of calcific tendinitis involving bone.

MATERIALS AND METHODS

We retrospectively reviewed 50 cases of calcific tendinitis involving underlying bone. Clinical data reviewed included patient age and sex and lesion location. Images reviewed included radiographs (n = 44), CT scans (n = 13), MRIs (n = 16), and bone scintigrams (n = 13). Radiologic examinations were evaluated for the presence of cortical erosion, periosteal reaction, and marrow extension. Pathology confirmation was available in 37 cases.

RESULTS

The average age of patients was 50 years (range, 16-82 years), with 29 female patients (58%). Calcific tendinitis with associated bone involvement was seen most commonly in the femur (40%) and the humerus (40%). Concretions were most commonly solid-appearing (50%). Cortical erosion was the most common manifestation of osseous involvement (78% of cases). Marrow involvement was shown in 18 (36%) of 50 cases. Marrow extension was most commonly seen in the lesser and greater tuberosities of the humerus, which accounted for 61% (11/18) of cases. Focal increased radionuclide uptake was seen in 13 (100%) of 13 cases.

CONCLUSION

Calcific tendinitis presenting with osseous destruction, marrow changes, and soft-tissue calcifications may be confused with neoplasm both radiologically and pathologically. Recognition of the atypical presentation of this common disease may prevent unnecessary biopsy.

Imaging Characteristics of Spindle Cell Lipoma

OBJECTIVE

The objective of this article is to define the imaging characteristics of spindle cell lipoma on MRI and CT.

CONCLUSION

The diagnosis of spindle cell lipoma should be suggested when a well-defined complex fatty mass is found in the subcutis of a middle-aged man, especially if the mass is localized to the posterior neck. Intense enhancement of the nonadipose component further supports this diagnosis.

Diagnosis of occult bone metastases: positron emission tomography

The current standard of practice for the detection of osseous metastatic disease is the conventional bone scan of the entire body using technetium-99m methylene diphosphonate (Tc-99m MDP). Although Tc-99m MDP scintigraphy is sensitive for the detection of advanced skeletal metastatic lesions, early involvement may be missed because this technique relies on the identification of the osteoblastic reaction of the involved bone rather than the detection the tumor itself. Positron emission tomography (PET) has proven to be the gold standard in metabolic imaging. Fluorine -18 deoxyglucose (FDG) provides a means of quantitating the glucose metabolism, with the amount of tracer accumulation reflecting the glucose metabolism: high-grade malignancies tend to have higher rates of glycolysis than do low-grade malignancies and benign lesions; therefore, high-grade malignancies have greater uptake of FDG than that of low-grade or benign lesions. Positron emission tomography has been shown to be superior to scintigraphy in the detection of metastases because it detects the presence of tumor directly by metabolic activity, rather than indirectly by showing tumor involvement due to increased bone mineral turnover. This has allowed the detection of metastatic foci earlier with PET than with bone scintigraphy. Although the spectrum of PET applications is unknown, it now is approved for the diagnosis, staging and restaging of many common malignancies and has shown efficacy for the detection of osseous metastasis from several malignancies including lung carcinoma, breast carcinoma, and lymphoma.

From the archives of the AFIP: imaging of primary chondrosarcoma: radiologic-pathologic correlation

Chondrosarcoma is a malignant tumor that produces cartilage matrix, and lesions that arise de novo are called primary. Primary chondrosarcoma is the third most common primary malignant tumor of bone, constituting 20%-27% of all primary malignant osseous neoplasms. There are numerous types of primary chondrosarcomas, including conventional intramedullary, clear cell, juxtacortical, myxoid, mesenchymal, extraskeletal, and dedifferentiated. The conventional intramedullary chondrosarcoma is the most frequent type, and it most commonly involves the long bones or pelvis in up to 65% of cases. Although the pathologic appearance varies with specific lesion type, chondrosarcomas grow with lobular type architecture, and these hyaline cartilage nodules demonstrate high water content and peripheral enchondral ossification. Imaging features directly reflect this pathologic appearance, and the various subtypes often show distinctive features. Radiographic findings often suggest the diagnosis of chondrosarcoma because of identification of typical "ring-and-arc" chondroid matrix mineralization (representing the enchondral ossification) and aggressive features of deep endosteal scalloping and soft-tissue extension. These latter features are usually best assessed, as is lesion staging, with computed tomography (CT) or magnetic resonance (MR) imaging. CT is optimal to detect the matrix mineralization, particularly when it is subtle or when the lesion is located in anatomically complex areas. Both CT and MR imaging depict the high water content of these lesions as low attenuation and very high signal intensity with T2-weighting, respectively. Understanding and recognizing the spectrum of appearances of the various types of primary chondrosarcoma allow improved patient assessment and are vital for optimal clinical management including diagnosis, biopsy, staging, treatment, and prognosis.

Malignant fatty tumors: classification, clinical course, imaging appearance and treatment

Liposarcoma is a relatively common soft tissue malignancy with a wide spectrum of clinical presentations and imaging appearances. Several subtypes are described, ranging from lesions nearly entirely composed of mature adipose tissue, to tumors with very sparse adipose elements. The imaging appearance of these fatty masses is frequently sufficiently characteristic to allow a specific diagnosis, while in other cases, although a specific diagnosis is not achievable, a meaningful limited differential diagnosis can be established. The purpose of this paper is to review the spectrum of malignant fatty tumors, highlighting the current classification system, clinical presentation and behavior, treatment and spectrum of imaging appearances. The imaging review will emphasize CT scanning and MR imaging, and will stress differentiating radiologic features.

Postgraduate musculoskeletal fellowship training in the United States: current trends and future direction

OBJECTIVE

To document current postgraduate musculoskeletal training program (accredited and unaccredited) curricula and approaches to education.

DESIGN AND PATIENTS

Questionnaires were sent to all musculoskeletal training programs. Responses regarding radiology residency and fellowship program sizes, types of imaging and invasive procedures included, and other program parameters were solicited. Features of accredited and unaccredited programs were compared. Teaching approaches, including the use of web-based or distance learning were evaluated.

RESULTS

Twenty-nine (73%) of 40 musculoskeletal programs responded to the questionnaire. Twenty-eight percent of programs were accredited and 72% unaccredited. Radiology residencies were also present at all responding institutions (the majority had a class size of 4-8/year). Residency programs in related specialties included pathology 96%, orthopedics and rheumatology 90%, oncology 83% and pain management 69%. The majority (93-100%) provided training in radiography, MRI and CT. Spine MRI was included in 69% of programs, ultrasonography in 62% and positron emission tomography in 24%. Arthrography and diagnostic and therapeutic injections (100%) were included in all programs. Other invasive procedures, including spine and radiofrequency ablation, were offered less frequently. Teaching approaches included conferences (100%), journal clubs (62%), multidisciplinary conferences (45-90%), web-based learning (30%) and distance learning (7%). Forty-one percent of programs offered off-site rotations.

CONCLUSIONS

The majority of musculoskeletal training programs prepared trainees for private or academic practice. There are inconsistencies that could be improved to better prepare trainees for careers in musculoskeletal imaging.

MR imaging of fibroma of the tendon sheath

OBJECTIVE

The purpose of our study was to describe the MR imaging characteristics of fibroma of the tendon sheath.

CONCLUSION

The diagnosis of fibroma of the tendon sheath can be suggested when MR imaging reveals a focal nodular mass adjacent to a tendon sheath with decreased signal on all pulse sequences and little or no enhancement.

Imaging characteristics of cystic adventitial disease of the peripheral arteries: presentation as soft-tissue masses

OBJECTIVE

Our purpose was to identify the characteristic imaging features of cystic adventitial disease of the peripheral arteries.

CONCLUSION

Patients with cystic adventitial disease of the peripheral arteries often present for evaluation of soft-tissue masses involving the extremities. Noninvasive imaging reveals a characteristic appearance allowing confident diagnosis.

Soft tissue tumors of the lower extremities

MRI is the preferred modality for th eevaluation of a soft tissue mass following radiography. The radiologic appearance of certain soft tissue tumors or tumor-like processes may be sufficiently unique to allow a strong presumptive radiologic diagnosis. It must be emphasized that one cannot differentiate reliably between benign and malignant lesions on radiologic imaging alone. When a specific diagnosis is not possible, knowledge of tumor prevalence by location and age, with appropriate clinical history and radiologic features, can be used to establish a suitably ordered differential diagnosis.

Primary bone tumors of the lower extremities

The key to adequate and accurate evaluation, diagnosis, and treatment of bone tumors is an organized and integrated approach involving the surgeon, radiologist, and pathologist. The radiologist plays not only a valuable role in the diagnosis and preoperative staging of bone tumors but may also play a role in biopsy and treatment. Despite the wide variety of imaging modalities available today, radiographs remain the mainstay in the evaluation of osseous neoplasms. Advanced imaging is. however. very useful for staging purposes and for characterization of the internal characteristics of tumors and may aid significantly in limiting the differential diagnosis. Although a detailed discussion of all ofthe various bone tumors of the lower extremities is beyond the scope of this article, an attempt is made to provide a framework for a rational and comprehensive approach to these complicated but relatively uncommon lesions. Certain lesions with unique characteristics are discussed to facilitate the diagnostic process.

Imaging of fatty tumors: distinction of lipoma and well-differentiated liposarcoma

PURPOSE

To review the reliability of computed tomographic (CT) and magnetic resonance (MR) imaging features in distinguishing lipoma and well-differentiated liposarcoma.

MATERIALS AND METHODS

CT (n= 29) and MR (n = 40) images and radiographs (n = 28) of 60 patients with histologically verified fatty tumors (35 lipomas and 25 well-differentiated liposarcomas) were retrospectively reviewed in 31 females and 29 males (mean age, 56 years; age range, 1-88 years). Images were assessed for adipose tissue content, and non-fatty component was classified (thin and/or thick septa and nodular and/or globular components) as absent, mild, moderate, or pronounced. Also assessed were signal intensity and tissue attenuation of the fatty components and non-adipose elements.

RESULTS

Statistically significant imaging features favoring a diagnosis of liposarcoma included lesion larger than 10 cm (P <.001), presence of thick septa (P =.001), presence of globular and/or nodular non-adipose areas (P =.003) or masses (P =.001), and lesion less than 75% fat (P <.001). The most statistically significant radiologic predictors of malignancy were male sex, presence of thick septa, and associated non-adipose masses, which increased the likelihood of malignancy by 13-, nine-, and 32-fold, respectively. Both lipoma and liposarcoma demonstrated thin septa and regions of increased signal intensity on fluid-sensitive MR images.

CONCLUSION

A significant number of lipomas will have prominent non-adipose areas and will demonstrate an imaging appearance traditionally ascribed to well-differentiated liposarcoma. Features that suggest malignancy include increased patient age, large lesion size, presence of thick septa, presence of nodular and/or globular or non-adipose mass-like areas, and decreased percentage of fat composition.

Diagnosis of primary bone tumors with image-guided percutaneous biopsy: experience with 110 tumors

PURPOSE

To determine the diagnostic accuracy of image-guided percutaneous biopsy in 110 primary bone tumors of varying internal compositions.

MATERIALS AND METHODS

One hundred ten consecutive patients with primary bone tumors underwent biopsy with computed tomography (CT) or fluoroscopy. Ninety-one patients underwent surgical follow-up and 19 received medical treatment and underwent subsequent imaging studies. Final analysis of bone biopsy results included tumor type, malignancy, final tumor grade, biopsy complications, and effect on eventual treatment outcome.

RESULTS

Seventy-seven tumors were malignant and 33 were benign. Most common tumors at biopsy were osteosarcoma (n = 20), lymphoma (n = 18), chondrosarcoma (n = 16), and giant cell tumor (n = 16). Correct final diagnosis was attained in 97 (88%) patients. Sixty-three lesions were solid nonsclerotic; 26, sclerotic; and 21, lytic with cystic centers containing internal areas of fluid, hemorrhage, or necrosis. In six of 21 lesions with a predominant cystic internal composition, problems occurred in determining a final diagnosis. In 13 patients, definite correct diagnosis was not obtained with initial percutaneous bone biopsy. Of these patients, benign bone tumors were better defined with surgical specimens in seven, a diagnosis of malignancy was changed to that of another malignancy in four, and the diagnosis was changed from benign to malignant in two. Nine patients underwent open surgical biopsy. Seven of the difficult cases were of cystic tumors with hemorrhagic fluid levels visible at CT or magnetic resonance imaging. The only complication was a small hematoma.

CONCLUSION

Percutaneous biopsy of primary bone tumors is safe and accurate for diagnosis and grade of specific tumor. In cases with nondiagnostic biopsy, open-procedure biopsy is likely to be associated with similar diagnostic difficulties.

Intramuscular myxoma: characteristic MR imaging features

OBJECTIVE

The purpose of our study was to identify the characteristic MR imaging features of intramuscular myxoma.

MATERIALS AND MATERIALS

We retrospectively reviewed the MR imaging features of 20 patients with intramuscular myxoma. Clinical assessment included the age and sex of the patient and location of the tumor. Radiologic evaluation included the lesion size and shape, border definition, signal on T1- and T2-weighted or fluid-sensitive MR sequences, enhancement pattern, presence or absence of a fat rind, and presence or absence of increased signal in the adjacent muscle on T2-weighted or fluid-sensitive MR sequences.

RESULTS

The mean age of patients presenting with intramuscular myxoma was 61 years (range, 15-85 years; median, 64 years). The mean lesion size was 6.9 cm (range, 3-17 cm; median, 6.3 cm). A peritumoral fat rind was present in 13 of the patients (65%) with myxoma, and an increased signal in the adjacent muscle on fluid-sensitive sequences was present in 11 patients (55%). Intramuscular myxomas were homogeneously low in signal intensity on T1-weighted MR sequences in 19 patients (95%), with all lesions showing a high signal intensity on T2-weighted or fluid-sensitive MR sequences. Twelve of the myxomas had well-defined borders, and eight had borders that were partially ill defined. Of the 11 lesions imaged after gadolinium administration, six (55%) showed intense heterogeneous enhancement.

CONCLUSION

Findings of a mass that on MR images shows a perilesional fat rind, the signal intensity of fluid, and an increased signal in the adjacent muscle on T2-weighted or fluid-sensitive MR sequences are strongly suggestive of intramuscular myxoma. The degree of lesion enhancement varies but is most frequently intense and heterogeneous. Although the recognition of these features likely will not obviate biopsy of any individual lesion, it will allow more accurate prebiopsy diagnosis and preoperative planning.

Wooden foreign bodies: imaging appearance

OBJECTIVE

The purpose of this study was to identify the characteristic imaging features of wooden foreign bodies.

MATERIALS AND METHODS

The imaging studies of 12 patients with surgically confirmed wooden foreign bodies were retrospectively reviewed. The study group consisted of seven females and five males, 10-65 years old (mean age, 36 years). All patients underwent radiography. Nine patients were evaluated with sonography, eight with MR imaging, three with CT, and one with CT arthrography. Gadolinium-enhanced MR imaging was performed in six patients. Three patients presented with a draining sinus and nine with painful swelling. Only three patients presented with a history of penetrating injury.

RESULTS

Lesions were located in the foot (n = 4), hand (n = 3), thigh (n = 2), calf (n = 2), and elbow (n = 1). Radiographs failed to reveal the retained foreign bodies in all patients. With MR imaging, wooden foreign bodies displayed a variable signal intensity that was equal to or less than that of skeletal muscle on both T1- and T2-weighted images. MR imaging showed the surrounding inflammatory response in all patients. CT showed the retained wood as linear cylindric foci of increased attenuation. Wood was highly echogenic and revealed pronounced acoustic shadowing on sonography. Arthrography in one patient showed an associated reactive synovitis.

CONCLUSION

The imaging appearance of wooden foreign bodies is variable; however, imaging can be quite specific, and when taken in the appropriate clinical setting, the imaging should reliably suggest the diagnosis. Sonography is frequently underused but proved most useful for the evaluation of retained wooden foreign bodies.

From the archives of AFIP. Imaging of giant cell tumor and giant cell reparative granuloma of bone: radiologic-pathologic correlation

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.

Imaging of musculoskeletal fibromatosis

The musculoskeletal fibromatoses comprise a wide range of lesions with a common histopathologic appearance. They can be divided into two major groups: superficial and deep. The superficial fibromatoses are typically small, slow-growing lesions and include palmar fibromatosis, plantar fibromatosis, juvenile aponeurotic fibroma, and infantile digital fibroma. The deep fibromatoses are commonly large, may grow rapidly, and are more aggressive. They include infantile myofibromatosis, fibromatosis colli, extraabdominal desmoid tumor, and aggressive infantile fibromatosis. Radiographs typically reveal a nonspecific soft-tissue mass, and calcification is common only in juvenile aponeurotic fibroma. Advanced imaging (ultrasonography, computed tomography, and magnetic resonance [MR] imaging) demonstrates lesion extent. Involvement of adjacent structures is common, reflecting the infiltrative growth pattern often seen in these lesions. MR imaging may show characteristic features of prominent low to intermediate signal intensity and bands of low signal intensity representing highly collagenized tissue. However, fibromatoses with less collagen and more cellularity may have nonspecific high signal intensity on T2-weighted images. Local recurrence is frequent after surgical resection due to the aggressive lesion growth. It is important for radiologists to recognize the imaging characteristics of musculoskeletal fibromatoses to help guide the often difficult and protracted therapy and management of these lesions.

Imaging of Soft Tissue Neoplasms in the Adult: Malignant Tumors

This review discusses the spectrum of malignant soft tissue tumors usually found in adults. Lesions most commonly identified in the pediatric population, as well as tumorlike masses, are not covered. Rather than presenting a complete review, the focus of this discussion is on common lesions and those lesions in which the diagnosis may be suggested on the basis of imaging. Diagnoses covered include malignant fibrous histiocytoma, fibrosarcoma, dermatofibrosarcoma protuberans, liposarcoma, synovial sarcoma, malignant peripheral nerve sheath tumor, leiomyosarcoma, aggressive vascular tumors, extraskeletal chondrosarcoma and osteosarcoma, lymphoma, and metastatic carcinoma.