Imaging of the skeletal muscle metastases.

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.