Adrenal Imaging

Diagnostic dilemmas: a multi-institutional retrospective analysis of adrenal incidentaloma pathology based on radiographic size

Introduction/background

Adrenal incidentalomas (AIs) are masses > 1 cm found incidentally during radiographic imaging. They are present in up to 4.4% of patients undergoing CT scan, and incidence is increasing with usage and sensitivity of cross-sectional imaging. Most result in diagnosis of adrenal cortical adenoma, questioning guidelines recommending removal of all AIs with negative functional workup. This retrospective study analyzes histological outcome based on size of non-functional adrenal masses.

Material and methods

10 years of data was analyzed from two academic institutions. Exclusion criteria included patients with positive functional workups, those who underwent adrenalectomy during nephrectomy, < 18 years, and incomplete records. AI radiologic and histologic size, histologic outcome, laterality, imaging modality, gender, and age were collected. T-test was used for comparison of continuous variables, and the two-sided Fisher’s exact or chi-square test were used to determine differences for categorical variables. Univariate analysis of each independent variable was performed using simple logistic regression.

Results

73 adrenalectomies met the above inclusion criteria. 60 were detected on CT scan, 12 on MRI, and one on ultrasound. Eight of 73 cases resulted in malignant pathology, 3 of which were adrenocortical carcinoma (ACC). Each ACC measured > 6 cm, with mean radiologic and pathologic sizes of 11.2 cm and 11.3 cm. Both radiologic and pathologic size were significant predictors of malignancy (p = 0.008 and 0.011).

Conclusions

Our results question the generally-accepted 4 cm cutoff for excision of metabolically-silent AIs. They suggest a 6 cm threshold would suffice to avoid removal of benign lesions while maintaining sensitivity for ACC.

Large adrenal mass heralding the diagnosis of occult extra-adrenal malignancy in two patients

We report two cases highlighting the role of fluorine-18-fluorodeoxyglucose positron emission tomography/computerised tomography (18F FDG PET/CT) in the diagnostic and preoperative workup of indeterminate adrenal masses. Case 1: a 60-year-old man was diagnosed with a large left-sided adrenal mass with indeterminate radiological characteristics on CT. Biochemical investigations ruled out tumour hypersecretion. 18F FDG PET/CT was performed to exclude metastases and identified a pulmonary nodule in the left upper lobe. Histology of the resected adrenal tumour demonstrated a secondary metastasis from an adenocarcinoma of the lung. Case 2: an 88-year-old male was found to have a heterogeneous and vascular left-sided suprarenal mass and a smaller right-sided adrenal nodule. Both adrenal nodules had indeterminate radiological characteristics. Biochemical investigations were negative. PET/CT demonstrated high avidity in the bilateral adrenal nodules but no extra-adrenal FDG avid disease. Histology demonstrated a metastatic carcinoma of pulmonary origin.