 Introduction/Background An adrenal incidentaloma is an unsuspected asymptomatic mass, usually detected on a radiologic study that was obtained for purposes unrelated to adrenal disease [1,2]. The prevalence of incidentally discovered adrenal masses ranges from 4% to 10% on radiological studies, depending on patient age, and from 1% to 8.7% in autopsy specimens [3]. The majority of incidentalomas are benign and most are nonhyperfunctioning adenomas. The prevalence of adenomas in the general population ranges from 1% to 2% [4], although autopsy studies have shown rates as high as 6.6% to 8.7%, depending on the age distribution of the patients. The risk of primary adrenocortical carcinoma in the general population is quite small, on the order of 0.06%; however, among patients with known adrenal masses, the risk is reported to be as high as 4.7% [4]. Other adrenal malignancies, such as angiosarcoma, lymphoma, and pheochromocytoma, are rare in the general population. Many other criteria are involved in the assessment of incidental adrenal masses, including size, growth or stability, and endocrine function. Size is an important variable in predicting malignancy of an incidentally discovered adrenal mass. Smaller lesions are usually benign [11]; therefore, incidental adrenal masses with <1 cm short axis measurement do not generally require further evaluation because of the overwhelming likelihood that these lesions are benign [12]. Conversely, larger lesions have a greater likelihood of being malignant. In addition, interval growth of adrenal masses has also been advocated as a potential indicator of malignancy. If prior imaging is available, and a lesion has been stable for 1 year or more, it can generally be considered benign [12,13]. Even though incidentally discovered adrenal masses are by definition asymptomatic, a proportion will show subclinical function. Current guidelines from the Association of Clinical Endocrinologist and American Association aCleveland Clinic, Cleveland, Ohio.
Adrenal Mass Evaluation.  Introduction/Background An adrenal incidentaloma is an unsuspected asymptomatic mass, usually detected on a radiologic study that was obtained for purposes unrelated to adrenal disease [1,2]. The prevalence of incidentally discovered adrenal masses ranges from 4% to 10% on radiological studies, depending on patient age, and from 1% to 8.7% in autopsy specimens [3]. The majority of incidentalomas are benign and most are nonhyperfunctioning adenomas. The prevalence of adenomas in the general population ranges from 1% to 2% [4], although autopsy studies have shown rates as high as 6.6% to 8.7%, depending on the age distribution of the patients. The risk of primary adrenocortical carcinoma in the general population is quite small, on the order of 0.06%; however, among patients with known adrenal masses, the risk is reported to be as high as 4.7% [4]. Other adrenal malignancies, such as angiosarcoma, lymphoma, and pheochromocytoma, are rare in the general population. Many other criteria are involved in the assessment of incidental adrenal masses, including size, growth or stability, and endocrine function. Size is an important variable in predicting malignancy of an incidentally discovered adrenal mass. Smaller lesions are usually benign [11]; therefore, incidental adrenal masses with <1 cm short axis measurement do not generally require further evaluation because of the overwhelming likelihood that these lesions are benign [12]. Conversely, larger lesions have a greater likelihood of being malignant. In addition, interval growth of adrenal masses has also been advocated as a potential indicator of malignancy. If prior imaging is available, and a lesion has been stable for 1 year or more, it can generally be considered benign [12,13]. Even though incidentally discovered adrenal masses are by definition asymptomatic, a proportion will show subclinical function. Current guidelines from the Association of Clinical Endocrinologist and American Association aCleveland Clinic, Cleveland, Ohio.