title: The serratus anterior muscle on chest radiographs.
abstract: The radiographic appearance of the serratus anterior muscle shadow is analyzed. In frontal and near-frontal views, it produces a "bowling-pin" silhouette. When the muscle is well developed, the medial edge of this silhouette may be superimposed upon the air shadow of the lung in a variety of ways. When it overlies the apex of the lung, it gives rise to the companion shadow; when overlying the midlateral lung edge and costophrenic angle it may mimic pleural and/or extrapleural disease. Recognition of the various possible patterns is important to prevent overdiagnosis of disease, particularly asbestosis.
mesh_terms: D001195:Asbestosis / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D006801:Humans; D009132:Muscles / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D010995:Pleural Diseases / Q000000981:diagnostic imaging*; D013902:Radiography, Thoracic; D013909:Thorax / Q000033:anatomy & histology; D014056:Tomography, X-Ray