Objective: The purpose of this study was to determine the rate of malignancy in incidentally detected bilateral adrenal masses in patients with no known history of cancer.
Materials and methods: A retrospective search of CT reports of patients with incidentally detected bilateral adrenal nodules was performed from January 1, 2002, to January 1, 2014. Patients were excluded if they had a known cancer or suspected functioning adrenal tumor; 161 patients were included. Nodules were characterized as benign or malignant on the basis of imaging features at the index CT examination, imaging features at subsequent adrenal protocol CT or MRI, imaging stability for a minimum of 1 year, or clinical follow-up of a minimum of 2 years.
Results: Mean nodule size was 1.8 cm (range, 0.7-4.9 cm). There were no cases of primary or secondary adrenal malignancy (95% CI, 0.00-0.023). The nodules diagnosed on index CT scans were 73 adrenal adenomas and two myelolipomas. Seventy-four nodules were subsequently characterized as adrenal adenomas on the basis of imaging findings. Of the 113 indeterminate nodules that had imaging follow-up, 111 were stable at the latest follow-up examination. One nodule grew 26% over 8.1 years, and the other grew 59% over 12.4 years. Clinical follow-up of patients with 60 indeterminate nodules revealed no evidence of adrenal malignancy.
Conclusion: No case of malignancy was found in 322 incidentally detected bilateral adrenal nodules at CT of patients without known cancer. Imaging follow-up of such lesions may be unnecessary.
Keywords: adrenal nodule; bilateral; incidental; incidentaloma; indeterminate.