Background: Adrenal masses are common incidental findings on radiologic imaging. The association between malignancy and hormonal hyperactivity found in incidentally discovered adrenal tumors, however, remains unclear. Methods: A retrospective analysis of prospectively collected data from patients who underwent adrenalectomy for incidentally discovered adrenal tumors at a single institution. Outcomes and operative data were compared by univariate analysis. Area under the curve was used to analyze the effect of tumor size in predicting malignancy. Results: There were 49 patients who initially presented with adrenal incidentalomas that underwent adrenalectomy. Most patients were Caucasian women with an average age of 51 ± 14 years. Of this group, 24 patients underwent resection for hyperfunctioning adrenal glands. There were no significant differences in malignancy rates between hyperfunctional and nonfunctional tumors (4.1% vs. 12.0%, P = 0.32). On final histopathology, there were four patients with adrenal malignancies: two adrenocortical carcinomas and two metastatic from renal carcinoma. Only one patient with a hyperfunctioning adrenal tumor had underlying malignancy. Overall, invasion of adjacent structures (P < 0.001), presence of lymphadenopathy (P = 0.02), metastasis (P = 0.03), irregular tumor margins (P = 0.01), heterogeneity (P = 0.05), and tumor size >6 cm (P = 0.04) on radiologic imaging were strongly associated with malignancy in adrenal incidentalomas. Conclusions: The risk of concomitant malignancy and hormonal hyperactivity in adrenal incidentalomas is very low. Tumor size (>6 cm) and radiographic features remain the most important predictors of adrenal malignancy, regardless of tumor function.
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