18F-fluorodeoxyglucose positron emission tomography as a diagnostic tool for malignancy of adrenocortical tumours? Preliminary results in 13 consecutive patients.

DESIGN This study is a preliminary report on 18F-fluorodeoxyglucose (18F-FDG) uptake for the characterization of hypersecretory or non-hypersecretory adrenocortical masses in patients without known neoplastic disease, thereby minimizing the presence of adrenal metastases, and without phaeochromocytoma, in comparison with computed tomography (CT) scanning and with iodocholesterol scintigraphy. METHODS Thirteen consecutive patients with an adrenal mass scheduled to have surgery, underwent hormonal exploration, a CT scan for tumour size measurement and an 18F-FDG positron emission tomography scan. Eleven of these patients also had unenhanced density measurement at CT scan and iodocholesterol scintigraphy. RESULTS CT-scanned adrenal masses ranged in size from 2.2 to 10 cm; attenuation value was <10 Hounsfield units (HUs) in two cases and >10 HU in nine. All benign lesions demonstrated iodocholesterol uptake. In the case of malignant tumours, results were non-homogeneous: no uptake, uptake and non-informative scintigraphy. All patients with an adrenocortical carcinoma had positive adrenal 18F-FDG uptake (n=3), one had a liver metastasis with positive 18F-FDG uptake, one showed 18F-FDG uptake in an adrenal metastasis from an unknown primary kidney tumour. All patients with a benign adrenocortical lesion had negative 18F-FDG uptake (n=9). Patients' lesions were hypersecretory (n=5), or non-hypersecretory (n=8), regardless of the pathology. CONCLUSION This short preliminary study indicates that 18F-FDG gave a correct classification of tissue characterization with accurate identification of malignant lesions, as well as the disease stage (metastasis or primary). These promising preliminary results on adrenocortical lesions, seldom studied with 18F-FDG, are to be confirmed in larger series.