CT determination of intrathoracic mass origin, mediastinum of lung

Computed tomographic determination of the origin of intrathoracic masses near to the mediastinial border is occasionally difficult. To establish the criteria for such differentiation, CT findings were evaluated in 32 cases with intrathoracic lesions (16, mediastinal and 16, pulmonary). So called extrapleural sign, i.e. pencil sharp convex outline and tapering margin, was valuable for this purpose. In addition, a fat pad sign (triangular fat at margin displaced by the mass) was equally useful for differentiation of the mass origin. (author)