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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. [ABSTRACT FROM AUTHOR]

We reviewed retrospectively the magnetic resonance (MR) images of 14 soft-tissue lesions of fibromatosis (desmoid tumors) encountered in 11 patients. The lesions were typically inhomogeneous in texture and round to oval in configuration. Margins were well-defined in 78% of the lesions at presentation and were infiltrating in all recurrences. On T1-weighted spin echo MR images, the predominant signal intensity was either isointense or minimally hyperintense when compared with skeletal muscle. On T2-weighted MR images the predominant signal intensity was typically intermediate between skeletal muscle and subcutaneous fat or isointense to fat. Linear and curvilinear areas of decreased signal intensity were distributed throughout the lesions on both pulse sequences in 86% of cases. This pattern strongly suggested fibromatosis. Speculation concerning possible etiologies of this appearance are discussed, and the relevant literature on previously reported cases is reviewed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Gout is a common inflammatory crystal deposition disease that occurs in many joints throughout the body. Active gout is most often associated with painful synovitis causing searing joint pains, but gout can also produce large masses of space-occupying deposits called tophi. Tophi are most frequently seen in juxta-articular locations with or without bony erosion and are often misdiagnosed as degenerative joint disease. Soft tissue deposits and tendon involvement are also known manifestations of gout, but can present with indeterminate and alarming findings on imaging. We present three cases of tophaceous gout mimicking aggressive neoplasms in the extensor mechanism of the knee. All cases presented as extensor tendon masses eroding into the patella, with imaging findings initially concerning for primary musculoskeletal malignancy.