You are in: eMedicine Specialties > Radiology > GENITOURINARY Adrenal AdenomaArticle Last Updated: Jun 10, 2005AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Perry J Horwich, MD, Staff Physician, Instructor of Radiology, Department of Radiology, Beth Israel - Deaconess Medical Center Perry J Horwich is a member of the following medical societies: American College of Radiology, International Society for Magnetic Resonance in Medicine, and Radiological Society of North America Coauthor(s): Stephen A Okon, MD, Consulting Staff, Assistant Professor of Radiology, Department of Radiology, Beth Israel Medical Center Editors: Glenn Krinsky, MD, Chief of Abdominal Imaging Section, Associate Professor, Department of Radiology, New York University School of Medicine; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Arnold C Friedman, MD, FACR, Associate Chairman, Department of Radiology, University of Florida Health Science Center; Chief, Department of Radiology, Shands-Jacksonville Hospital; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Consulting Staff, Department of Radiology, Virginia Mason Medical Center Author and Editor Disclosure Synonyms and related keywords: adrenal cortical nodular hyperplasia, adrenal tumor, adrenal gland tumor, benign adrenal tumor, adrenal cortical adenoma INTRODUCTIONSection 2 of 12
  BackgroundAdrenal cortical adenoma is a common benign tumor arising from the cortex of the adrenal gland. It commonly occurs in adults, but it can be found in persons of any age. Adrenal cortical adenomas are benign neoplasms; they are not considered to be potentially malignant. Benign adrenal cortical adenoma can be diagnosed with a high degree of specificity, which ranges from 95-99%, and with a sensitivity of greater than 90%. These impressive percentages are a result of the relatively common prevalence of adrenal adenomas in the general population and the extensive radiologic research with primarily CT and MRI imaging methods. The adrenal gland is the fourth most common site of metastasis, and adrenal metastases may be found in as many as 25% of patients with known primary lesions. Therefore, radiologists frequently face the task of determining whether an adrenal mass is benign or malignant. The question can directly affect the clinical management of the case. For instance, the workup for an otherwise resectable lung cancer may reveal the presence of an adrenal mass and suggest the possibility of metastatic disease. The differential diagnosis of adrenal masses includes many primary, metastatic, benign, and malignant entities, most of which are not discussed at length here. Instead, this article includes practical information that pertaining specifically to adrenal adenomas. PathophysiologyBenign adrenal cortical adenomas are commonly smaller than 6 cm in diameter on initial presentation, but they may be larger. The presence of an adrenal cortical adenoma should be correlated with the clinical presentation and, if necessary, serum chemical and urinalysis results in assessing the presence of a functional adenoma. Nonfunctional adrenal cortical adenomas are not premalignant, and surgical excision is not indicated. Histologically, 2 types of adrenal cortical adenomas are identified: those that contain a high percentage of intracytoplasmic lipid, which represent approximately 70% of all adrenal cortical adenomas, and those that do not have this high percentage, which represent the remaining 30%. The presence of intracytoplasmic lipid is fairly specific for adrenal cortical adenomas; therefore, other processes, such as metastasis, hemorrhage, and other primary adrenal neoplasms, have distinctly different imaging characteristics. This unique difference allows clinicians to use imaging techniques that demonstrate lipid to distinguish adenomas from other processes that affect the adrenal gland. The major exception is clear cell carcinoma of the kidney, which contains an abundance of intracytoplasmic lipid; when these metastasize to the adrenal gland, their behavior can be identical to that of a lipid-rich adenoma. Note that, on CT scans and MRIs, the appearance of intracytoplasmic lipid is different from that of macroscopic fat, as in the case of a myelolipoma. FrequencyUnited StatesAdrenal masses are a common finding on cross-sectional abdominal images. In about 1-5% of all cases, abdomen CT scans that are obtained for reasons other than the evaluation for possible adrenal neoplasm demonstrate an adrenal mass. On autopsy, 2-10% of cases involve a benign cortical adrenal adenoma. SexEvidence suggests that the incidence in teenage girls is slightly higher that that of teenage boys, but no sex-related predilection is found in adults. AgeAdrenal cortical adenoma commonly occurs in adults, but it can be present in individuals of any age. AnatomyThe adrenal glands are located in the perirenal space near the upper pole of each kidney. They are varied in their appearance. They may be shaped like the letters H, L, Y, T, or V. Typically, they are less than 4 cm in length and less than 1.0 cm in width. Preferred ExaminationThe modalities of choice in the evaluation of an adrenal mass are CT, MRI, and positron emission tomography (PET). Ultrasonography has a role in the evaluation of a potential adrenal mass in infants, but no appearance is specific for benign adrenal adenoma. How should the radiologist proceed in evaluating an incidental small adrenal mass? Two important questions must be answered. First, does the patient have a hormonal or biochemical abnormality that may be caused by an enlarged adrenal gland? If this is the case, the lesion should be surgically removed regardless of the imaging features. Second, does the patient have a known malignancy? In the absence of a known malignancy, the probability that a small well-circumscribed adrenal mass is malignant is nearly zero. The characterization of an adrenal mass is critical in patients with a known malignancy in whom the diagnosis of an adrenal metastasis precludes curative surgery. The authors of a prominent review article suggest that CT without intravenous contrast enhancement should be the initial study. If the adrenal mass is less than 10 HU, a diagnosis can be made. If the adrenal mass is more than 10 HU, CT with intravenously administered contrast material should follow, and the washout should be calculated. In cases in which CT findings are equivocal, chemical shift MRI should be performed. When the findings of both modalities are inconclusive, biopsy is advised only when a known extra-adrenal malignancy is present. Limitations of TechniquesObvious considerations include the availability and cost of CT and MRI. A delay in CT imaging can potentially diminish the efficiency of the CT schedule, result in multiple examinations, and expose the patient to ionizing radiation. MRI examination may enable diagnosis without exposing the patient to ionizing radiation; however, MRI may not be as available as CT, and it can be more expensive. DIFFERENTIALSSection 3 of 12
Adrenal Carcinoma Adrenal Hemorrhage Adrenal Metastases Adrenal Myelolipoma Hyperaldosteronism Neuroblastoma Pheochromocytoma
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Media file 1: Homogeneous, well-defined, 7-HU ovoid mass is seen in the right adrenal gland; this finding is diagnostic of a benign adrenal adenoma. (Image was obtained in the same patient as in Image 2.) | |
 | View Full Size Image | Media type: CT |
| Media file 2: Homogeneous, well-defined, 7-HU, ovoid mass is seen in the right adrenal gland; this finding is diagnostic of a benign adrenal adenoma. (CT scan obtained in the same patient as in Image 1.) | |
 | View Full Size Image | Media type: CT |
| Media file 3: Contrast-enhanced CT scan demonstrates a homogeneously enhancing ovoid mass in the left adrenal gland. As in this case, attenuation measurements of adrenal masses on contrast-enhanced CT scans are frequently nondiagnostic. (Image was obtained in the same patient as in Images 4 and 5.) | |
 | View Full Size Image | Media type: CT |
| Media file 4: Contrast-enhanced CT scan demonstrates a homogeneously enhancing ovoid mass in the left adrenal gland. As in this case, attenuation measurements of adrenal masses on contrast-enhanced CT scans are frequently nondiagnostic. (Image was obtained in the same patient as in Images 3 and 5.) | |
 | View Full Size Image | Media type: CT |
| Media file 5: MRIs obtained with in-phase (left) and out-of-phase (right) imaging after CT imaging. Note how the signal intensity in the left adrenal mass (white arrow) decreases (ie, the mass is darker) relative to that of the spleen on the out-of-phase images. As in this case, a signal intensity decrease of 20% or greater is diagnostic of a benign adrenal adenoma. (Image was obtained in the same patient as in Images 3 and 4.) | |
 | View Full Size Image | Media type: MRI |
| Media file 6: Homogeneously enhancing ovoid mass is seen in the left adrenal gland. (Image was obtained in the same patient as in Images 7 and 8.) | |
 | View Full Size Image | Media type: CT |
| Media file 7: Homogeneously enhancing ovoid mass is seen in the left adrenal gland. (Image was obtained in the same patient as in Images 6 and 8.) | |
 | View Full Size Image | Media type: CT |
| Media file 8: An adrenal adenoma (arrows) is diagnosed with follow-up MRI when decreased signal intensity is seen on the out-of-phase image. (Image was obtained in the same patient as in Images 6 and 7.) | |
 | View Full Size Image | Media type: CT |
| Media file 9: MRI images demonstrate a homogeneous ovoid mass in the right adrenal gland (arrows). A concomitant loss of signal intensity, relative to that of the spleen, with out-of-phase imaging is diagnostic of benign adrenal adenoma. | |
 | View Full Size Image | Media type: MRI |
| Media file 10: Dynamic and delayed contrast-enhanced CT scans demonstrate a homogeneously enhancing mass in the right adrenal gland. The degree to which enhancement diminishes over time is referred to as washout, which can be calculated by using the following formula: [1 - (attenuation at 10 minutes/attenuation at 80 seconds)] X 100, where the attenuations are in Hounsfield units. In this case, the washout equals [1 – (36/99)] X 100, or 64%. Findings from a recent publication in a major journal suggests that any washout greater than 50% is diagnostic of a benign adrenal adenoma. Further studies are needed to confirm these promising results. | |
 | View Full Size Image | Media type: CT |
Article Last Updated: Jun 10, 2005
