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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 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.

Context: Most adrenal incidentalomas are nonfunctioning adrenocortical adenomas (ACAs). Adrenocortical carcinomas (ACCs) are rare but should be recognized at an early stage. Objective: The objective of the study was to evaluate the usefulness of 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) to predict malignancy in patients without a previous history of cancer. Design: This was a prospective, multicenter study from 2001 to 2006. Setting: The study was conducted at a network of seven university hospitals in Paris. Patients: Seventy-seven patients were included. All underwent surgery because of hypersecretory and/or growing benign lesions (n = 18), obvious ACCs (n = 21), or radiologically indeterminate lesions (n = 38). Main Outcome Measure: The degree of 18F-FDG PET uptake [maximum standardized uptake value (maxSUV)] was related to the pathological findings serving as a reference, and its diagnostic value was compared with that of computerized tomography (CT) scan. Results: Pathology eventually diagnosed 43 ACAs, 22 ACCs, and 12 nonadrenocortical lesions. Using a cutoff value above 1.45 for adrenal to liver maxSUV ratio, the sensitivity and specificity to distinguish ACAs from ACCs were, respectively, 1.00 (95% confidence interval 0.85–1.00) and 0.88 (95% confidence interval 0.75–0.96). Among the 38 indeterminate lesions at CT scan, we could analyze a subgroup of 16 adrenocortical tumors with high unenhanced density (>10 HU) and an inappropriate washout: 18F-FDG PET correctly predicted the benignity in 13 of 15 ACAs. Conclusions: In a multidisciplinary team approach, 18F-FDG PET helps to manage suspicious CT scan lesions. An adrenal to liver maxSUV ratio less than 1.45 is highly predictive of a benign lesion.