Dopamine-secreting glomus vagale: a case report and histopathologic correlation

Dopamine-Secreting Pheochromocytoma and Paraganglioma

Predominantly or exclusively dopamine-secreting pheochromocytoma and paraganglioma are very rare. We report a 64-year-old woman with an adrenal incidentaloma. She was normotensive and had no symptoms of catecholamine excess. The 24-hour urine catecholamine level showed normal norepinephrine (122.9 μg/day), normal epinephrine (24.3 μg/day), and markedly elevated dopamine (148 212.4 μg/day). ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy revealed tumor uptake. After α-blockade as preoperative management, she successfully underwent laparoscopic left adrenalectomy and was finally diagnosed with an exclusively dopamine-secreting pheochromocytoma. The tumor was histologically comprised of small polygonal cells with high cellularity and was immunohistochemically positive for all 3 catecholamine-synthesizing enzymes: tyrosine hydroxylase (very weak), dopamine β-hydroxylase (heterogeneous), and phenylethanolamine N-methyltransferase (very weak). Electron microscopy revealed very few catecholamine-containing small vesicles with a few organelles, which reflected immature cells. No biochemical or imaging evidence of recurrence or metastasis were evident 1 year after the surgery. We conducted a literature search in the PubMed database. A total of 33 cases were collected. Our case had the second-highest 24-hour urinary dopamine excretion and was the first in which immunostaining for catecholamine synthase and electron microscopy were performed together. Histological findings in our case give a possible hypothesis that the mechanism underlying a dopamine-secreting pheochromocytoma is associated with immature catecholamine vesicles in which dopamine β-hydroxylase is localized, thus resulting in inhibited conversion from dopamine to norepinephrine. We also discuss the reasons for the lack of catecholamine excess symptoms, whether preoperative management of α-blockade is needed, and the association between the prognosis and genetic mutation, with an extensive literature review.

Secreting vagal paraganglioma

Paragangliomas are rare tumors that derive from neural crest tissue. Vagal paragangliomas account for only 3% of all head and neck paragangliomas. Patients with vagal paragangliomas typically present with an asymptomatic neck mass and, less frequently, with cranial neuropathies. It is estimated that only 1% to 3% of all head and neck paragangliomas secrete catecholamines. The incidence of secreting vagal paragangliomas is even smaller. The diagnosis of a secreting paraganglioma involves the use of a screening test for serum catecholamines and a 24-hour urinary test for catecholamine metabolites. The identification and staging of these tumors can be performed through the use of MRI and/or CT scans and an octreotide scintigraphy. The mainstay treatment is surgical extirpation; however, preoperative medical blockade is critical to avoid a hypertensive crisis intra-operatively. We present two illustrative cases of secreting vagal paragangliomas involving a complex diagnostic and therapeutic algorithm.