CT identifies prevalence of incidental adrenal masses

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Incidental adrenal masses seen on abdominal CT scans of low-risk patients are almost always benign and do not need any imaging follow-up, according to a large study of patients published in the May issue of the American Journal of Roentgenology.

The purpose of the study was to determine the nature and prevalence of adrenal lesions identified on CT in patients with no known malignancy. The finding is significant because incidental adrenal lesions are seen in about 5 percent of CT exams, according to the study’s lead author, Julie H. Song, MD, of the department of diagnostic imaging, at Rhode Island Hospital and Warren Alpert Medical School of Brown University in Providence, R.I.

The study included 973 patients with 1,049 adrenal masses, who had no history of malignancy or clinical suspicion of a hormonally active adrenal mass. All masses were confirmed as benign either histopathologically, by imaging follow-up or clinical follow-up, Song and colleagues wrote.

Most of the lesions (75 percent) were adenomas (; the second most common mass was myelolipomas. “Myelolipomas were found in 6 percent of the patients, which makes it more common than previously thought,” Song and colleagues said.

A computer search of abdominal CT reports using the term "adrenal" was performed in 65,231 consecutive patients with examinations performed from January 2000 to December 2003. An adrenal mass was identified in 3,307 (5 percent) patients. Patients with no known malignancy and no suspicion for a hyperfunctioning adrenal mass were further isolated. Nine hundred seventy-three patients with 1,049 adrenal masses fulfilled the study criteria. The nature of each lesion was determined by histopathology; imaging characterization with CT, MRI, or washout; a minimum of one year of stability on follow-up imaging; or clinical follow-up of at least two years.

According to the results, 1,049 adrenal masses were characterized with the following methods: histopathology ( n = 12), imaging characterization ( n = 909), imaging follow-up ( n = 87), and clinical follow-up ( n = 41). There were 788 adenomas constituting 75 percent of all lesions. There were 68 myelolipomas (6 percent), 47 hematomas (4 percent), and 13 cysts (1%). Three pheochromocytomas (0.3 percent) and one cortisol-producing adenoma (0.1 percent) were found incidentally. One hundred twenty-eight lesions (12%) were presumed to be benign by imaging or clinical stability.

In 973 consecutive patients with an incidental adrenal mass and no history of cancer, the researchers did not identify any malignant lesions, even among the 14 patients who later developed malignancy elsewhere. Adenomas (75 percent) and myelolipomas (6 percent) were the most common lesions, according to Song and colleagues.