Raised dopamine metabolites in a case of malignant paraganglioma

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.

Metastatic pheochromocytoma/paraganglioma related to primary tumor development in childhood or adolescence: significant link to SDHB mutations

PURPOSE

To present data on the high rate of SDHB mutations in patients with metastatic pheochromocytoma/paraganglioma whose initial tumor presentation began in childhood or adolescence.

PATIENTS AND METHODS

From 2000 to 2010, 263 patients with pheochromocytoma/paraganglioma were evaluated through the National Institutes of Health (NIH), Bethesda, MD. Of the 263 patients, 125 patients were found to have metastatic disease; of these 125 patients, 32 patients presented with a tumor before 20 years of age. An additional 17 patients presented with a tumor before 20 years of age but demonstrated no development of metastatic disease. Genetic testing for mutations in the VHL, MEN, and SDHB/C/D genes was performed on patients without previously identified genetic mutations.

RESULTS

Of the 32 patients who presented with metastatic disease and had their primary tumor in childhood or adolescence, sequence analysis of germline DNA showed SDHB mutations in 23 patients (71.9%), SDHD mutations in three patients (9.4%), VHL mutations in two patients (6.3%), and an absence of a known mutation in four patients (12.5%). The majority of these 32 patients (78.1%) presented with primary tumors in an extra-adrenal location.

CONCLUSION

The majority of patients with metastatic pheochromocytoma/paraganglioma who presented with a primary tumor in childhood/adolescence had primary extra-adrenal tumors and harbored SDHB mutations. Except for primary tumors located in the head and neck where SDHD genetic testing is advised, we recommend that patients who present with metastatic pheochromocytoma/paraganglioma with primary tumor development in childhood or adolescence undergo SDHB genetic testing before they undergo testing for other gene mutations, unless clinical presentation or family history suggests a different mutation.