BERKELEY, CA (UroToday.com) - Adrenal adenoma, adrenocortical carcinoma, pheochromocytoma and neuroblastoma are four discrete adrenal neoplasms that have the potential for functional activity. Functional adrenal neoplasms may secrete cortisol, aldosterone, sex-hormones or catecholamines. This heterogeneous group of tumors demonstrate variable biologic behavior and clinical outcomes. These neoplasms are encountered with increasing clinical frequency due to an expansion in the volume of medical imaging performed. Therefore, a clinical understanding of adrenal neoplasms is essential. In our article, we discuss these functional adrenal neoplasms with particular attention devoted to their clinical features and imaging findings.
Adrenal adenomas are benign adrenal cortical neoplasms representing 50-80% of all adrenal neoplasms. Functioning adenomas are symptomatic due to excess secretion of cortisol, aldosterone or sex-hormones. Adenomas can be categorized as lipid rich (70%) or lipid poor (30%) depending on the intracellular fat content. Lipid rich adenomas have a low attenuation, less than 10 Hounsfield Units (HU) on unenhanced CT. Chemical-shift MRI imaging and CT washout studies can also be utilized to distinguish adenomas from other neoplasms.
Adrenocortical carcinomas (ACCs) are rare malignant neoplasms, and approximately 60% of these are functional. Cortisol is the most common hormone produced and causes Cushing’s disease in 30-40%. On Imaging, ACCs are typically large, inhomogenous with ill-defined margins, and demonstrate heterogeneous enhancement. ACCs show > 10 HU on unenhanced CT and exhibit slow contrast washout. On MRI, ACCs are usually hypointense on T1- and heterogeneously hyperintense on T2-weighted images. 18F-2-fluoro-2-deoxy-D-glucose positron emission tomography (18FDG-PET) is a functional imaging modality used for detecting metabolically active neoplasms. When combined with CT, 18FDG PET-CT has a high specificity and sensitivity in differentiating ACCs from adenomas.
Pheochromocytomas are neuroendocrine neoplasms of chromaffin tissue of the adrenal medulla. Most pheochromocytomas are hormonally active and secrete catecholamines, epinephrine, and norepinephrine, manifesting as clinical triad of headaches (60-90%), palpitations (50-70%) and diaphoresis (55-75%). On MRI, pheochromocytomas are classically described as showing low-signal intensity on T1- and high-signal intensity equivalent to cerebrospinal fluid on T2- weighted images - ‘light bulb’ bright. This classical appearance is found in approximately one-third of cases. Most pheochromocytomas show avid contrast enhancement and slow contrast washout. 123/131I-metaiodobenzylguanidine (MIBG) scintigraphy is widely used, demonstrating high sensitivity and specificity in imaging pheochromocytomas.
Neuroblastomas are heterogeneous neoplasms with a broad spectrum of biologic behavior, seen predominantly in pediatric population. An asymptomatic palpable mass in the abdomen is the most common clinical finding. Metastatic disease is present in 50-60% at diagnosis and may be the cause of the initial clinical complaint. An invasive suprarenal mass demonstrating stippled calcifications in a young child is the classic imaging finding. CT and MRI typically show a lobulated heterogeneous enhancing mass with internal hemorrhage and necrosis. Neuroblastomas show high uptake on MIBG scintigraphy with high sensitivity and specificity reported.
The key radiologic observations of each of these neoplasms are illustrated using multi-modality images. Familiarity with the clinical and imaging features of these neoplasms improves diagnosis and facilitates appropriate clinical decision-making and patient management.
Kamal Sahi, MD and Gavin Low, MBChB, MRCS, FRCR* as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Department of Radiology & Diagnostic Imaging
University of Alberta Hospital