Metastasis or adenoma? Computed tomographic evaluation of the adrenal mass
Anne A. Singer, MDAddress reprint requests to A.A.S., Department of Diagnostic Radiology, Hb6, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195.
Nancy A. Obuchowski, PhD
David M. Einstein, MD
David M. Paushter, MD
Determining the nature of an adrenal mass is often a clinical challenge.OBJECTIVE
To determine if unenhanced computed tomographic (CT) scanning can differentiate benign adenomas from metastases.METHODS
Twenty-four pathologically proven adrenal masses were retrospectively correlated with their appearance on unenhanced CT scanning.RESULTS
Metastases were significantly larger than adenomas and had higher attenuation coefficients. A sensitivity-to-specificity ratio of 33:100 was achieved at a threshold of 0 Hounsfield units (HU), while a threshold of 10 HU produced a ratio of 58:92. A threshold size of 2.5 cm produced a ratio of 58:100. Attenuation and size were the only useful criteria for differentiating adenomas from metastases.CONCLUSION
Measuring the size and attenuation of adrenal masses can help identify benign adenomas. Lesions exceeding specific thresholds may still be benign and may require biopsy. We advocate documenting lesion stability for longer than is usually done, as one metastatic lesion remained without significant change in appearance for 18 months.