IMAGING

The incidental indeterminate adrenal mass on CT (> 10 H) in patients without cancer: is further imaging necessary? Follow-up of 321 consecutive indeterminate adrenal masses
Song JH, Chaudhry FS, Mayo-Smith WW
Department of Diagnostic Imaging, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, RI, USA
AJR Am J Roentgenol. 2007; 189: 1119-23

• Objective: The objective of our study was to determine whether follow-up imaging evaluation is necessary for incidentally discovered indeterminate adrenal lesions (> 10 H) on CT in patients with no known malignancy.
• Materials and Methods: A computer search of CT reports from January 2000 to December 2003 identified patients with incidentally detected, indeterminate, but benign-appearing adrenal lesions who had no known malignancy and no clinical suspicion of hyperfunctioning adrenal mass. Patients with adrenal masses diagnostic on the initial CT or heterogeneous masses were excluded. Two hundred ninety patients with 321 lesions met the study criteria. Each lesion was determined to be benign or malignant based on histopathology, characterization with diagnostic imaging studies, or a minimum of 1 year of stability on imaging follow-up or 2 years of stability on clinical follow-up.
• Results: Of the 321 lesions, 318 masses (99.1%) were confirmed to be benign and clinically insignificant. These included three (0.9%) histologically confirmed adenomas, 198 (61.7%) adenomas by imaging characterization, five (1.6%) other benign lesions, 71 (22.1%) masses stable on imaging follow-up, and 41 (12.8%) masses with clinical stability. There were three (0.9%) clinically unsuspected functioning masses: one cortisol-producing adenoma and two pheochromocytomas. There were no metastatic adrenal lesions, even among the 13 patients who subsequently developed malignancy elsewhere.
• Conclusion: All of the incidentally detected adrenal masses with a CT attenuation of > 10 H were benign in patients with no known malignancy. Follow-up imaging to characterize an incidental adrenal mass appears to have a limited role in this patient cohort.
  
  
• Editorial Comment
  Adrenal incidentalomas are found in up to 5% of abdominal CT examination and most of these adrenal lesions observed in patients with no known malignancy are presumed to be benign adenomas as long as they appears as homogeneous, well-defined lesion, round or oval, less than 3 cm, and with attenuation equal or below 10UH. Nowadays imaging plays an essential role for the accurate characterization of the nature of these incidentalomas. The imaging armamentarium used for this evaluation includes unenhanced CT, chemical shift MRI, CT histogram and CT contrast washout analysis. More recently, promising results of MR spectroscopic imaging have been reported, adding to the armamentarium of adrenal imaging (1).There is still controversies regarding how to follow these patients presenting with radiologic diagnosis of adrenal adenoma; some radiologists do not suggest any follow-up, others recommends repeat dedicated imaging studies at 6, 12, and 24 months. As pointed out by the authors of this manuscript the American College of Radiology states that extensive and costly workup is usually not justified for small (< 3 cm) adrenal masses. The authors of this interesting retrospective study state that none of the adrenal masses (with CT attenuation of > 10UH) incidentally detected in patients without cancer were malignant. Similar findings have been reported in other series in the literature. The authors also did not find any case of a primary adrenal cortical carcinoma or found any enlargement of the lesion in the follow-up study, although enlargement of 1 cm over 1 year can be found in 5% of benign adenomas. Although this study has important limitation already highlighted by the authors (lack of routine biochemical screening in all patients, absence of follow-up in 32 patients, and short follow-up in 66 patients), their results are challenging and calls for further prospective studies to confirm that all small adrenal lesions incidentally found in patients with not known cancer need no follow-up imaging or at least need a less rigid scheme of imaging follow-up.

References
1. Faria JF, Goldman SM, Szejnfeld J, Melo H, Kater C, Kenney P, et al: Adrenal masses: characterization with in vivo proton MR spectroscopy—initial experience. Radiology. 2007; 245: 788-97.

Dr. Adilson Prando
Chief, Department of Radiology and
Diagnostic Imaging
Vera Cruz Hospital
Campinas, São Paulo, Brazil
E-mail: aprando@mpc.com.br