Endocrine Abstracts

Introduction: The investigation and management of large adrenal lesions varies widely. It is appropriate to have a low threshold for surgical removal of large adrenal lesions with the possible exception of stable adrenomyelipomata. 18F-FDG PET is increasingly used as an imaging technique to assess these lesions. We would like to highlight the potential benefits and pitfalls of using 18F-FDG PET as part of the diagnostic pathway.

Method: Since 2008, 18F-FDG PET scans have been used in the department, as part of the assessment of large adrenal masses where the diagnosis remains uncertain (e.g. 18F-FDG PET scans are not performed in cases with elevated metanephrines suggestive of a phaeochromocytoma). 8 patients who had 18F-FDG PET for large adrenal masses measuring more than 5 cm between 2008 and 2011 were looked at retrospectively. The degree of uptake on 18F-FDG PET scan was correlated with the histopathological diagnosis.

Results: Five of the six patients, with a histopathological diagnosis of adrenalcortical carcinoma (ACC) had a moderate to high uptake on 18F-FDG PET. One patient with probable ACC had no uptake on 18F-FDG PET but histology confirmed a globally necrotic neoplasm. Two patients with no uptake or low grade uptake had ganglioneuromas on histology. One of these was a 19 year old female with a surgically inaccessible adrenal mass. An adrenal biopsy confirmed the diagnosis and avoided the need for complex surgery.

Discussion: Moderate to high uptake on 18F-FDG PET scans predicted which adrenal masses were ACC and confirmed the appropriateness of adrenalectomy. The first case illustrates that a negative 18F-FDG PET may still be in keeping with a probable ACC (although the degree of necrosis made the malignant potential uncertain). A negative FDG PET should certainly alert the endocrinologist to a wider potential differential diagnosis. In the second case, intervention with a biopsy led to conservative management.

Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.