Editing Adrenal: Pheochromocytoma (section)

=== Imaging ===

* '''18F-FDG PET''' (fluorine-18 fluorodeoxyglucose positron emission tomography)
** '''Gold standard imaging modality for definitive staging in patients with pheochromocytoma.'''
** Superior test characteristics to CT, MRI, and metaiodobenzylguanidine (MIBG) scintigraphy.
** Better accuracy than 123I-MIBG in nearly all patients, especially for identification of metastatic disease.[[File:Pheochromocytoma Scan.jpg|alt=Pheochromocytoma MIBG|thumb|Pheochromocytoma (dark circular shadow near body center) localized by MIBG scintigraphy. See corresponding CT below. Source: [[commons:File:Pheochromocytoma_Scan.jpg|Wikipedia]]]]
* '''MIBG'''
** Utilizes a small-molecule analog of norepinephrine
** High specificity but low sensitivity for diagnostic disease identification.
** '''Useful modality when a suspected pheochromocytoma cannot be localized or when metastatic disease is suspected.'''
*** '''In the most common and urologically most relevant clinical scenario, a solitary adrenal mass on cross sectional imaging in the setting of a biochemical evaluation indicative of pheochromocytoma, MIBG or 18F-FDG PET may be safely be omitted''' '''because these functional studies only serve to confirm what is already known and do not alter management.''' '''However, MIBG or 18F-FDG PET imaging for large (>5 cm) tumors is likely prudent to assess for metastatic disease before surgery and thereby counsel the patient appropriately'''

* '''MRI'''
** Distinct low signal intensity on T1-weighted imaging
** '''High signal intensity on T2-weighted imaging.'''
* '''CT'''
** '''On unenhanced CT, pheochromocytomas are typically > 10 HU''' (mean ≈35 HU) given their rich vascularity and low lipid content. This can help differentiate them from lipid-rich adenomas
*** '''If the lesion is not an adenoma, an adrenal mass protocol CT with IV contrast allows for evaluation of tumor washout.'''
**** '''Benign adrenal lesions wash out >50% on delayed imaging while pheochromocytoma, adrenocortical carcinoma and metastatic tumors do not.'''
*** [[File:Phaeochromozytoma CT coronal.jpg|thumb|CT scan with enhancement demonstrating suspicous left adrenal mass. See corresponding MIBG scan above. Source: [[commons:File:Phaeochromozytoma_CT.jpg|Wikipedia]]]]'''Pheochromocytomas usually measure greater than 10 HU on unenhanced CT and >100 HU on contrast imaging,''' and are often well circumscribed in appearance with or without necrotic or cystic elements. Nevertheless, any evaluation of an adenoma should still include testing for plasma free metanephrines to rule out pheochromocytoma.

* CT scan with enhancement demonstrating suspicious left adrenal mass.  See corresponding MIBG scan above.  Source: Wikipedia