RESUMO
AIM: To define the radiological imaging features and clinical findings of the patients with skeletal muscle metastasis. MATERIALS AND METHODS: 4454 computed tomography (CT), 1802 magnetic resonance imaging (MRI) and 2569 positron emission tomography/computed tomography (PET/CT) imaging studies of the oncology patients performed between March 2009 and July 2012 in the Radiology and Nuclear Medicine Departments of our hospital were retrospectively reviewed. RESULTS: Fifty-two patients had 91 different metastatic skeletal muscle masses. Twenty-one patients (40%) were diagnosed with lung carcinoma as being the most common primary source. Forty-seven patients (90%) had metastatic disease somewhere else at the time of detection of skeletal muscle metastasis. Thirty-three patients (63%) had lymph node metastasis which was the most common site. Muscles mostly affected by metastatic disease were gluteals (15%), psoas (8.7%), erector spinae (8.7%), rectus abdominis (7.6%), latissimus dorsi (6.5%). The mean size of the lesions was 30 mm (range, 10-120 mm). The most common appearance on contrast-enhanced CT was a rim-enhancing intramuscular mass with central hypoattenuation. On MRI, skeletal muscle metastases mostly revealed isointense signal on T1-weighted images, heterogeneous high signal with peritumoral edema on T2-weighted images and extensive enhancement with central necrosis on gadolinium-DTPA (diethylene triamine pentaacetic acid) enhanced images. CONCLUSIONS: Skeletal muscle metastasis may be an incidental finding on CT. The most common CT appearance is a rim-enhancing intramuscular mass with central hypoattenuation. On MRI, extensive tumoral enhancement, central necrosis and peritumoral edema are highly acceptable features of skeletal muscle metastasis.