Radiographic Characteristics of Adrenal Masses in Oncologic Patients

BACKGROUND: We aimed to assess the usefulness of pre-contrast Hounsfield unit (HU) and mass size on computed tomography to differentiate adrenal mass found incidentally in oncologic patients. METHODS: From 2000 to 2012, 131 oncologic patients with adrenal incidentaloma were reviewed retrospectively. Receiver operating characteristic (ROC) curves were applied to determine the optimal cut-off value of the mean HU and size for detecting adrenal metastasis. RESULTS: The median age was 18 years, and 80 patients were male. The initial mass size was 18 mm, and 71 (54.2%) of these were on the left side. A bilateral adrenal mass was found in 11 patients (8.4%). Biochemically functional masses were observed in 9.2% of patients. Thirty-six out of 119 patients with nonfunctional masses underwent adrenalectomy, which revealed metastasis in 13. The primary cancers were lung cancer (n=4), renal cell carcinoma (n=2), lymphoma (n=2), hepatocellular carcinoma (n=2), breast cancer (n=1), and others (n=2). The area under the curve for the size and HU for clinically suspicious metastasis were 0.839 (95% confidence interval [CI], 0.761 to 0.900; P<0.001) and 0.959 (95% CI, 0.898 to 0.988; P<0.001), respectively. The cut-off value to distinguish between metastasis and benign masses were 22 mm for size and 20 for HU. CONCLUSION: ROC curve results suggest that pre-contrast HU >20 can be used as a diagnostic reference to suggest metastasis in oncologic patients with adrenal masses.