Once the biochemical diagnosis of a catecholamine-secreting tumor is confirmed, localization studies should be performed.
Computed tomography (CT) imaging or magnetic resonance imaging (MRI) of the abdomen and pelvis (at least through the level of the aortic bifurcation) are the most commonly used methods for localization. Both have similar sensitivities (90%-100%) and specificities (70%-80%).
CT imaging provides excellent anatomic detail. MRI provides good anatomic detail.
Additional functional imaging may be necessary if CT imaging or MRI fails to localize the tumor. It might also be useful in patients who are at risk for multifocal, malignant, or recurrent disease. 123 I-metaiodobenzylguanidine (MIBG) scintigraphy coupled with CT imaging provides anatomic and functional information with good sensitivity (80%-90%) and specificity (95%-100%).
131 I-MIBG can be used in the same way, but the image quality is not as high as with 123 I-MIBG. Other functional imaging alternatives include 111 In-octreotide scintigraphy and 18 F-fluorodeoxyglucose positron emission tomography, both of which can be coupled with CT imaging for improved anatomic detail. It is rare for localization of a catecholamine-secreting tumor to be unsuccessful if currently available imaging methods are used.
It has been proposed that all patients diagnosed with a pheochromocytoma or paraganglioma should consider genetic testing because the incidence of a hereditary syndrome in apparently sporadic cases is as high as 25%.[8,9,30] Early identification of a hereditary syndrome allows for early screening for other associated tumors and identification of family members who are at risk. In addition, some patients with a hereditary syndrome are more likely to develop multifocal, malignant, or recurrent disease. Knowledge of the specific genetic mutation permits increased vigilance during preoperative localization or postoperative surveillance of such patients.
Certain subgroups of patients are at very low risk of having an inherited syndrome (e.g., <2% in patients diagnosed with apparently sporadic pheochromocytoma after age 50 years). Therefore, genetic testing for all patients diagnosed with a pheochromocytoma or paraganglioma may not be practical or cost effective from a population standpoint. It is currently recommended that every patient diagnosed with a pheochromocytoma or extra-adrenal paraganglioma should first undergo risk evaluation for a hereditary syndrome by a certified genetic counselor.
Genetic testing is recommended in the following situations:
- Patients with a personal or family history of clinical features suggestive of a hereditary pheochromocytoma-paraganglioma syndrome.
- Patients with bilateral or multifocal tumors.
- Patients with sympathetic or malignant extra-adrenal paragangliomas.
- Patients diagnosed before age 40 years.
In patients with a unilateral pheochromocytoma and no personal or family history suggestive of hereditary disease, genetic testing can be considered if patients are between the ages of 40 years and 50 years, but genetic testing is not recommended if patients are older than 50 years. If a mutation is identified, predictive genetic testing should be offered to asymptomatic at-risk family members.