Metabolic and anatomic characteristics of benign and malignant adrenal masses on positron emission tomography/computed tomography: a review of literature

Abstract

PET/CT with (18)F-fluorodeoxyglucose (FDG) or using different radiocompounds has proven accuracy for detection of adrenal metastases in patients undergoing cancer staging. It can assist the diagnostic work-up in oncology patients by identifying distant metastases to the adrenal(s) and defining oligometastatic disease that may benefit from targeted intervention. In patients with incidentally discovered adrenal nodules, so-called adrenal "incidentaloma" FDG PET/CT is emerging as a useful test to distinguish benign from malignant etiology. Current published evidence suggests a role for FDG PET/CT in assessing the malignant potential of an adrenal lesion that has been 'indeterminately' categorized with unenhanced CT, adrenal protocol contrast-enhanced CT, or chemical-shift MRI. FDG PET/CT could be used to stratify patients with higher risk of malignancy for surgical intervention, while recommending surveillance for adrenal masses with low malignant potential. There are caveats for interpretation of the metabolic activity of an adrenal nodule on PET/CT that may lead to false-positive and false-negative interpretation. Adrenal lesions represent a wide spectrum of etiologies, and the typical appearances on PET/CT are still being described, therefore our goal was to summarize the current diagnostic strategies for evaluation of adrenal lesions and present metabolic and anatomic appearances of common and uncommon adrenal lesions. In spite of the emerging role of PET/CT to differentiate benign from malignant adrenal mass, especially in difficult cases, it should be emphasized that PET/CT is not needed for most patients and that many diagnostic problems can be resolved by CT and/or MR imaging.

High False Positivity in Positron Emission Tomography is a Potential Diagnostic Pitfall in Patients with Suspected Adrenal Metastasis

“…From our analysis, patients with primary lung malignancy had almost 11 times greater chance of harboring an adrenal metastasis than those with non-lung primary malignancy. This is consistent with the finding that lung primary malignancy is the most common malignancy metastasizing to the adrenals [1][2][3][10][11] . Using an optimal cut-off of 2.65, those with SUVmax >2.65 had a 31.6 times greater chance of adrenal metastasis than those with SUVmax ≤2.65.…”

“…Our data found that the history of primary lung malignancy (odds ratio=11.91, 95%CI 1.30 -111. 1) and SUVmax (odds ratio=1.66, 95%CI=1.09 -2.52) were significant risk factors for adrenal metastasis. From our analysis, patients with primary lung malignancy had almost 11 times greater chance of harboring an adrenal metastasis than those with non-lung primary malignancy.…”

“…an adrenal lesion not apparent from previous CT scans if available), a lesion with interval enlargement (which was defined as >20% increase in any one dimension over one year or by pro rata if duration was not exactly one year), a large lesion (i.e. ≥4.0cm in the largest dimension) and a lesion with indeterminate CT features (such as attenuation by Hounsfield unit > 10 on noncontrast CT scan and / or absolute washout pattern > 60% or relative washout > 40% on contrast CT scan) 1,3 . Characteristics such as age, sex, main reason for suspecting adrenal metastasis, type of primary non-adrenal malignancy, PET/CT findings and final adrenal pathology of the eligible patients were extracted from patient charts.…”

“…The adrenal gland is a common site for metastasis in patients with malignancy. It is estimated that up to 50% of all adrenal masses incidentally detected in patients with history of malignancy would harbor metastases [1][2][3] . Since adrenalectomy for solitary adrenal metastasis offers survival benefit in selected patients [4][5] , establishing whether these adrenal masses are in fact metastatic or not is clinically important.…”

Surgical resection of metastases to the adrenal gland: a single center experience

“…Lin et al observed that FDG-PET/CT was not able to differentiate between benign and malignant lesions in patients with HCC [16]. However, FDG-PET/CT emerged as an adjunctive diagnostic tool in the evaluation of incidental adrenal lesions in order to distinguish benign from malignant adrenal nodules and for the overall preoperative staging [17,18]. Therefore, FDG-PET/CT is currently used more frequently, e.g., in patients with bronchial tumors.…”