The location of middle mediastinal pheochromocytomas.

Eight middle mediastinal pheochromocytomas were located by means of 131I- meta- iodobenzylguanidine scintigraphy. The exact anatomic location of the lesions was confirmed by means of dynamic computed tomographic scanning following bolus injection of contrast medium. In all but one case the lesion had not been detected prior to scintigraphy despite extensive investigations including arteriography, venography with sampling, computed tomography with infusion of contrast medium, and in some cases surgical exploration of the abdomen and chest. Accurate anatomic location of the lesion permitted resection of five lesions from the cardiac atria and one from the aortopulmonary window. A sixth case in which an atrial pheochromocytoma was found by coronary angiography was not cured by resection of the primary tumor, and 131I- meta- iodobenzylguanidine scintigraphy revealed extensive metastases. Thus 131I- meta- iodobenzylguanidine scintigraphy has been of considerable value in the location of pheochromocytomas of the middle mediastinum, which may be a more frequent site than previously recognized.