From the Guidelines
The diagnosis of pheochromocytoma (chromocytoma) is made through a combination of biochemical testing, imaging studies, and sometimes genetic testing, with the initial diagnosis typically beginning with measuring elevated levels of catecholamines or their metabolites in blood or urine, including plasma free metanephrines and urinary metanephrines, as recommended by the most recent guidelines 1. The biochemical tests are highly sensitive for detecting the tumor, with plasma free metanephrines having a sensitivity of 96%−100% and specificity of 89%−98% 1. Once biochemical evidence suggests pheochromocytoma, imaging studies such as CT scan, MRI, or functional imaging like MIBG (metaiodobenzylguanidine) scan are performed to locate the tumor, typically found in the adrenal glands 1. In some cases, genetic testing may be recommended as approximately 40% of pheochromocytomas are associated with inherited syndromes. Key points to consider in the diagnosis of pheochromocytoma include:
- Measuring plasma free metanephrines and urinary metanephrines as the initial biochemical tests 1
- Using clonidine-suppression testing to further evaluate suspected cases with elevated catecholamine metabolites 1
- Pursuing imaging studies only after biochemical evidence for a pheochromocytoma has been obtained 1
- Considering genetic testing in patients with a family history of PPGL or in carriers of a germline mutation in one of the PPGL-causing genes 1
From the Research
Diagnosis of Pheochromocytoma
The diagnosis of pheochromocytoma is made through a combination of biochemical tests, imaging studies, and genetic screening.
- Biochemical tests: Measurement of plasma or 24-hour urinary fractionated metanephrines is the best biochemical diagnostic test 2, 3, 4, 5, 6.
- Imaging studies: Computed tomography (CT) or magnetic resonance imaging (MRI) has high sensitivity (90-100%) and reasonable specificity (70-90%) for the anatomical localization of the tumor 2, 3, 4, 5.
- Functional imaging: Metaiodobenzylguanidine (MIBG) scintigraphy, positron emission tomography (PET), or single photon emission computed tomography (SPECT) are used to assess the functionality of the tumor 2, 3, 4, 5, 6.
- Genetic screening: Gene mutations are reported in 32-79% of cases, making genetic screening mandatory in all cases, especially in children, pregnant women, and older people 2, 3, 4, 5, 6.
Diagnostic Steps
The diagnostic steps for pheochromocytoma include:
- Measurement of catecholamines and their metabolites (metanephrines) in plasma and/or urine 3, 5, 6.
- Pharmacological testing (e.g., clonidine suppression test) may be indicated in patients with moderately elevated catecholamines or when the diagnosis is still uncertain 5.
- Imaging techniques such as abdominal CT scan, MRI, and MIBG-scanning are used to localize the tumor 3, 4, 5, 6.
- Nuclear imaging approaches, such as (123)I-metaiodobenzylguanidine scintigraphy and 6-[(18)F]fluorodopamine positron emission tomography, enhance both diagnosis and localization of the tumor 6.