Metastases are synonymous of malignant neoplasm in advanced stage and so associated with a poor prognosis. As the first manifestation of cancer disease, the muscle metastasis is very rare. The definitive diagnosis of its presence is made based on histology. The authors presented the case of a patient with a lung adenocarcinoma, being with first manifestation of it, a muscle metastasis only about a month later there were clinical manifestations with imaging appearance that led to the diagnosis of a primary neoplasm. The rare manifestation of the disease motivated the study and surveillance of the patient and lead to the diagnosis.