LARGE ADRENAL INCIDENTALOMAS REQUIRE A DEDICATED DIAGNOSTIC PROCEDURE.

INTRODUCTION: The management of large non secreting adrenal tumors (at least 4 cm) is still a matter of debate as it is unclear whether imaging, especially 18F-FDG, can be used to characterize their potential malignancy. Moreover, the risk of new hypersecretion in non-operated tumors is uncertain. Our aim was to better characterize these large adrenal incidentalomas.

METHODS: Patients followed in our Center for a non-secreting large (at least 4 cm) adrenal incidentaloma, with an initial CT and 18F-FDG PET CT, were retrospectively included. Patients who were not operated after initial diagnosis had to be followed with clinical, biological and imaging evaluations for at least 3 years or till delayed surgery.

RESULTS: 81 patients were included in the study: 44 patients (54.3%) had initial surgery while 37 were followed, including 21 (25.9%) who were operated after a mean of 19 months. Among the 65 operated patients, 13 (20%) had a malignant lesion (3 with metastasis, and 10 with adrenocortical carcinoma): unenhanced CT < 10 showed 85.6% sensitivity and 78.8% specificity; all had a 18F-FDG uptake ratio > 1.5. Among the 24 patients who were followed for at least 3 years, 5 (20.8%) finally presented hypercortisolism (4 subclinical).

CONCLUSIONS: As expected, large adrenal tumors are at higher risk of malignancy. The combination of unenhanced CT < 10 and 18 F-FDG PET ratio < 1.5 prove to be reassuring and might lead to a close follow-up rather than immediate surgery. Hormonal follow-up should be focused on the risk of hypercortisolism.