Incidental Adrenal Mass on CT: Adrenal Disease With No Known Malignancy
Incidental Adrenal Mass on CT: Adrenal Disease With No Known Malignancy
Objective: The purpose of our study was to determine the nature and prevalence of adrenal lesions identified on CT in patients with no known malignancy.
Materials and Methods: 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%) 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 1 year of stability on follow-up imaging; or clinical follow-up of at least 2 years.
Results: One thousand forty-nine 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% of all lesions. There were 68 myelolipomas (6%), 47 hematomas (4%), and 13 cysts (1%). Three pheochromocytomas (0.3%) and one cortisol-producing adenoma (0.1%) were found incidentally. One hundred twenty-eight lesions (12%) were presumed to be benign by imaging or clinical stability. No malignant adrenal masses were found, even among the 14 patients who later developed malignancy elsewhere.
Conclusion: In 973 consecutive patients with an incidental adrenal mass and no history of cancer, no malignant lesions were identified. Adenomas (75%) and myelolipomas (6%) were the most common lesions.
The adrenal gland is a common site of disease, with a prevalence of abnormality reported to be as much as 9% in autopsy series. With the increasing use of CT, adrenal lesions are frequently found in the daily practice of radiology, diagnosed on up to 5% of CT examinations performed for various reasons. Imaging features on CT can establish a specific diagnosis of many of these lesions, including myelolipoma, hematoma, and cysts. Once a diagnostic dilemma, now adenomas can be accurately diagnosed using unenhanced CT, chemical shift MRI, and CT contrast washout analysis. Because the adrenal gland is also a frequent site of metastasis, recent literature has focused on imaging characterization of adrenal masses to differentiate adenomas from metastases. In patients without known malignancy, most adrenal lesions are benign, and a specific diagnosis can now be made on the basis of imaging features.
However, there are scant data in the imaging literature about the prevalence of different adrenal masses. Much of the prevalence information quoted is derived from autopsy series from the 1950s and 1960s. In studies with imaging and surgical correlation, selection bias is frequently present because these surgical lesions are typically large or have malignant imaging features requiring histologic evaluation. In addition, many of these studies have a mixed population of low-risk and cancer patients. Prevalence of adrenal abnormalities is important to understand because the adrenal gland is a common site of disorders, and the increased use of cross-sectional imaging has increased the frequency of detection of adrenal lesions.
The purpose of our study was to determine the prevalence and cause of adrenal masses incidentally identified on CT in low-risk patients. The prevalence of disease is important in predicting the risk of malignancy when an adrenal mass is discovered in a patient without known cancer. Our hypothesis is that most of these incidentally found adrenal lesions are benign, and some of these benign lesions may be more prevalent than has been previously reported in the pathology literature.
Objective: The purpose of our study was to determine the nature and prevalence of adrenal lesions identified on CT in patients with no known malignancy.
Materials and Methods: 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%) 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 1 year of stability on follow-up imaging; or clinical follow-up of at least 2 years.
Results: One thousand forty-nine 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% of all lesions. There were 68 myelolipomas (6%), 47 hematomas (4%), and 13 cysts (1%). Three pheochromocytomas (0.3%) and one cortisol-producing adenoma (0.1%) were found incidentally. One hundred twenty-eight lesions (12%) were presumed to be benign by imaging or clinical stability. No malignant adrenal masses were found, even among the 14 patients who later developed malignancy elsewhere.
Conclusion: In 973 consecutive patients with an incidental adrenal mass and no history of cancer, no malignant lesions were identified. Adenomas (75%) and myelolipomas (6%) were the most common lesions.
The adrenal gland is a common site of disease, with a prevalence of abnormality reported to be as much as 9% in autopsy series. With the increasing use of CT, adrenal lesions are frequently found in the daily practice of radiology, diagnosed on up to 5% of CT examinations performed for various reasons. Imaging features on CT can establish a specific diagnosis of many of these lesions, including myelolipoma, hematoma, and cysts. Once a diagnostic dilemma, now adenomas can be accurately diagnosed using unenhanced CT, chemical shift MRI, and CT contrast washout analysis. Because the adrenal gland is also a frequent site of metastasis, recent literature has focused on imaging characterization of adrenal masses to differentiate adenomas from metastases. In patients without known malignancy, most adrenal lesions are benign, and a specific diagnosis can now be made on the basis of imaging features.
However, there are scant data in the imaging literature about the prevalence of different adrenal masses. Much of the prevalence information quoted is derived from autopsy series from the 1950s and 1960s. In studies with imaging and surgical correlation, selection bias is frequently present because these surgical lesions are typically large or have malignant imaging features requiring histologic evaluation. In addition, many of these studies have a mixed population of low-risk and cancer patients. Prevalence of adrenal abnormalities is important to understand because the adrenal gland is a common site of disorders, and the increased use of cross-sectional imaging has increased the frequency of detection of adrenal lesions.
The purpose of our study was to determine the prevalence and cause of adrenal masses incidentally identified on CT in low-risk patients. The prevalence of disease is important in predicting the risk of malignancy when an adrenal mass is discovered in a patient without known cancer. Our hypothesis is that most of these incidentally found adrenal lesions are benign, and some of these benign lesions may be more prevalent than has been previously reported in the pathology literature.
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