F-18 Fluorodeoxyglucose Positron Emission Tomography-Positive Benign Adrenal Cortical Adenoma: Imaging Features and Pathologic Correlation

Abstract

Accurate characterization of adrenal lesions in lung cancer is essential in the staging of the disease. Computed tomography and magnetic resonance imaging as well as fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging are used to differentiate adrenal metastases from benign adenomas. Although FDG-PET is highly accurate in this regard, benign adrenal cortical adenomas have been shown to accumulate FDG, although to a lesser degree. We present a patient with a history of lung cancer and FDG accumulation in a benign adenoma, probably reflecting areas of chronic inflammation also seen within the gland at pathology.

A black adrenal adenoma difficult to be differentiated from a malignant adrenal tumor by CT, MRI, scintigraphy and FDG PET/CT examinations

“…Five percent of adrenal abnormalities interpreted as positive at PET are false positive for malignancy [16]. This is secondary to not only adrenal adenoma [29,30] but also inflammatory lesions (tuberculosis, sarcoidosis), adrenal endothelial cysts, periadrenal abnormality, adrenal cortical hyperplasia, and schwannoma [31] because they have been associated with increased FDG uptake [16].…”

Use of [18F]Fluorodeoxyglucose Positron Emission Tomography in Evaluating Locally Recurrent and Metastatic Adrenocortical Carcinoma

“…Adrenal adenomas generally do not show abnormal metabolic activity, and hence, in the case of an enlarged adrenal gland, PET imaging may help to distinguish adenoma from carcinoma. In the rare cases in which an adrenal adenoma does show elevated metabolic activity on FDG PET, the activity may reflect inflammation within the lesion (21).…”

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

“…Unfortunately the utility of FDG PET/CT for adrenal mass evaluation is hampered by a small, though significant number of false positives due to adrenocortical adenomas, which may be functioning or non-functioning, with overlap between adenomas and malignancy. Several authors have described focal increased FDG uptake in a benign adrenal adenoma [150][151][152] and also in a rare black (pigmented) adrenal adenoma [153]. An adrenal adenoma with subclinical Cushing's syndrome also had increased FDG uptake with max SUV of 4.8, considered higher than normally seen with benign adrenal lesions [154].…”