A 65 year old woman with persistent hypertension was found to have an abnormality on chest radiograph. She underwent further evaluation with contrast-enhanced chest CT:
Here is the coronal reconstruction from the same study:
There is an avidly enhancing mediastinal mass at the aortopulmonary window/prevascular nodal stations, closely associated with the aortic arch.
Differential for an enhancing mediastinal mass includes: nodal metastasis from enhancing tumor (e.g. renal cell carcinoma), mediastinal parathyroid adenoma (See Endocrinology Case 5), bronchial carcinoid tumor, Castleman disease, and mediastinal paraganglioma.
Although history and laboratory studies may narrow this differential, what molecular imaging test can also help in the evaluation?
This patient underwent I-123 Meta-iodo-benzyl-guanidine (MIBG) imaging:
Note that the I-123 normal distribution classically includes myocardial uptake (due to adrenergic innervation), but this can be variable or absent with a very radiotracer-avid tumor, as in this case.
This is a patient with a mediastinal paraganglioma. This is an uncommon tumor arising from the sympathetic ganglia around the aorta, aortopulmonary window, or paraspinous regions. Catecholamine secretion can be diagnosed using serum/urine levels of metanephrines and other catecholamines. I-123 MIBG imaging is useful to evaluate for metastatic disease (absent in this case).
Classically in perioperative management of functional tumors, alpha-adrenergic blockade should be performed prior to beta-blockade (to avoid unopposed alpha stimulation and risk of hypertensive crisis).
Ziessman HA, O’Malley JP, Thrall JH, eds. Nuclear Medicine, the Requisites, 4th ed. Philadelphia: Elsevier, 2014.
Brown ML, et al. Mediastinal paragangliomas: the Mayo Clinic experience. Ann Thorac Surg 2008;86:946-51.