Skeletal Muscle Metastases from Carcinomas: A Review of the Literature.

* Bones are a common site for metastases; however, muscle metastases recently have been more commonly reported, not only as a result of the multidisciplinary approach in the treatment of these patients but also because of more sensitive imaging modalities such as positron emission tomography-computed tomography (PET-CT) that identify these lesions in early stages.* The most common carcinoma is lung carcinoma, with a hematogenous route of spread mainly to the axial region of the body (the psoas muscle, the gluteal muscles, and the paravertebral muscles). * Clinically, skeletal muscle metastases from carcinomas frequently present as painful palpable masses with or without swelling and are commonly found before diagnosis of the primary carcinoma.* Multiple imaging modalities, including radiographs, CT, magnetic resonance imaging (MRI), and PET-CT, have been used for diagnosis and staging, but tissue sampling is needed for a final diagnosis. The most important differential diagnosis of skeletal muscle metastases is with soft-tissue sarcomas.* Treatment is mainly based on chemotherapy and/or radiation; surgery is performed in cases of symptomatic lesions that fail to respond to nonoperative treatment.