Metastasis to the gluteus maximus muscle from renal cell carcinoma with special emphasis on MRI features

<p>Abstract</p> <p>Background</p> <p>The skeletal muscle is an unusual site for metastasis from renal cell carcinoma (RCC). Metastatic RCC must be differentiated from benign primary soft-tissue tumors because aggressive surgical resection is necessary.</p> <p>Case presentation</p> <p>We present the case of a 65-year-old man with metastatic RCC in the gluteus maximus muscle (3.8 cm in diameter) found on enhanced computed tomography (CT) 6 years after nephrectomy. Retrospectively, the small mass (1 cm in diameter) was overlooked 5 years earlier on enhanced CT. Because the growth of the lesion was slow, benign tumor was a differential diagnosis. However, magnetic resonance imaging (MRI) showed that the mass had high-signal intensity on T1- and T2-weighted images (WIs) compared to that of skeletal muscle, with mild enhancement by Gadolinium. The MRI features were unusual for most soft-tissue tumors having low-signal intensity on T1-WI and high-signal intensity on T2-WI. Therefore, under a diagnosis of metastatic RCC, the lesion was resected together with the surrounding skeletal muscle. The histology was confirmed to be metastatic RCC.</p> <p>Conclusion</p> <p>MRI features of metastatic RCC may be beneficial in differentiating it from primary soft-tissue tumor.</p

Pseudoaneurysm overlying an osteochondroma: a noteworthy complication

Pseuodaneurysms are an extremely rare complication of osteochondromas. We describe a case of traumatic pseudoaneurysm of the brachial artery presenting as a soft tissue mass in a patient who was treated for an osteochondroma 3 years earlier. This case demonstrates that radiographic follow-up of large osteochondromas is mandatory and that, in patients with soft tissue masses and a history of osteochondroma, pseudoaneurysms should be included in the differential diagnosis

MR imaging of clear cell sarcoma (malignant melanoma of the soft parts): a multicenter correlative MRI-pathology study of 21 cases and literature review.

textabstractObjective. To evaluate MR imaging and pathology findings in order to define the characteristic features of clear cell sarcoma of the soft tissues (malignant melanoma of the soft parts). Design and patients. MR examinations of 21 patients with histologically proven clear cell sarcoma of the musculoskeletal system were retrospectively reviewed and assessed for shape, homogeneity, delineation, signal intensities on T1- and T2-weighted images, contrast enhancement, relationship with adjacent fascia or tendon, secondary bone involvement, and intratumoral necrosis. In 19 cases the pathology findings were available for review and for a comparative MR-pathology study. Results. On T1-weighted images, lesions were isointense (n=3), hypointense (n=7) or slightly hyperintense to muscle (n=11). Immunohistochemical examination was performed in 17 patients. All 17 specimens showed positivity for HMB-45 antibody. In nine of 11 lesions with slightly increased signal intensity on T1-weighted images, a correlative MR imaging-pathology study was possible. All nine were positive to HMB-45 antibody. Conclusions. Clear cell sarcoma of the musculoskeletal system often has a benign-looking appearance on MR images. In up to 52% of patients, this lesion with melanocytic differentiation has slightly increased signal intensity on T1-weighted images compared with muscle. As the presence of this relative higher signal intensity on T1-weighted images is rather specific for tumors displaying melanocytic differentiation, radiologists should familiarize themselves with this rare entity and include it in their differential diagnosis when confronted with a well- defined, homogeneous, strongly enhancing mass with slightly higher signal intensity compared with muscle on native T1-weighted images