eMedicine Specialties > Radiology > Genitourinary

Adrenal Adenoma

Perry J Horwich, MD, Staff Physician, Instructor of Radiology, Department of Radiology, Beth Israel - Deaconess Medical Center
Stephen A Okon, MD, Consulting Staff, Assistant Professor of Radiology, Department of Radiology, Beth Israel Medical Center

Updated: May 4, 2009

Introduction

Background

Adrenal 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 not considered to have the potential for malignant transformation.

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 in Multimedia.)

Homogeneously enhancing ovoid mass is seen in the left adrenal gland. (Image was obtained in the same patient as in Images 6 and 8 in Multimedia.)

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 pertains specifically to adrenal adenomas.

Frequency

United States

Adrenal 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; the majority of these are adrenal adenomas. On autopsy, 2-10% of cases involve a benign cortical adrenal adenoma.

International

An Italian study of incidentally discovered adrenal masses among subjects undergoing chest CT scan found that the prevalence of adrenal adenomas was approximately 4%.¹

Sex

Evidence suggests that the incidence in teenage girls is slightly higher that that of teenage boys, but no sex-related predilection is found in adults.

Age

Adrenal cortical adenoma commonly occurs in adults, but it can be present in individuals of any age.

Presentation

Anatomy

The adrenal glands are located in the perirenal space near the upper pole of each kidney. Their appearance varies: they may be shaped like the letter H, L, Y, T, or V. Typically, they are less than 4 cm in length and less than 1.0 cm in width.

Pathophysiology

Benign adrenal cortical adenomas are commonly smaller than 6 cm in diameter on initial presentation, but they may be larger. Correlation with the clinical presentation and, if necessary, serum chemical and urinalysis results should be used to determine whether an adrenal cortical adenoma is functional. Nonfunctional adrenal cortical adenomas are not premalignant, and surgical excision is not indicated.

Histologically, adrenal cortical adenomas can be differentiated on the basis of intracytoplasmic lipid content. Approximately 70% of all adrenal cortical adenomas have a high percentage of intracytoplasmic lipid; the remaining 30% do not.

The presence of intracytoplasmic lipid is fairly specific for adrenal cortical adenomas; other processes, such as metastasis, hemorrhage, and other primary adrenal neoplasms, have distinctly different imaging characteristics. This unique characteristic allows clinicians to distinguish adenomas from other processes that affect the adrenal gland, by using imaging techniques that demonstrate lipid. 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 appearance 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.

Preferred Examination

The 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.^{2,3,4,5,6,7,8,9,10,11,12}

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.² If the adrenal mass is less than 10 Hounsfield units (HU), a diagnosis of adrenal adenoma 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; benign lesions typically demonstrate more than 50% washout. 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 Techniques

Obvious 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 can be more expensive.

Differential Diagnoses

Other Problems to Be Considered

Adrenal hemorrhage
Adrenal hyperplasia
Adrenal cyst
Infection (eg, tuberculosis, meningococci)

Radiography

Findings

Although plain radiographs can be useful in characterizing old adrenal hemorrhage or commonly calcified adrenal neoplasms, they have no significant role in the diagnosis of adrenal cortical adenoma.

Computed Tomography

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 in Multimedia.)

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 in Multimedia.)

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 in Multimedia.)

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 in Multimedia.)

Homogeneously enhancing ovoid mass is seen in the left adrenal gland. (Image was obtained in the same patient as in Images 7 and 8 in Multimedia.)

Homogeneously enhancing ovoid mass is seen in the left adrenal gland. (Image was obtained in the same patient as in Images 6 and 8 in Multimedia.)

Findings

CT is, along with MRI, one of the modalities of choice in diagnosing adrenal cortical adenoma.

On CT scans, adrenal cortical adenomas are well-circumscribed mass lesions that are homogeneous in their attenuation and enhancement patterns. The evaluation should be performed by using sections that are 5 mm or thinner to ensure that attenuation measurements are not affected by volume averaging. The use of a sufficient milliampere-second (mAs) setting is important so that the measured attenuation values do not have a significant standard deviation. Heterogeneous enhancement or attenuation can be observed when a lipid-rich adenoma and a lipid-poor adenoma coexist. A lesion that is poorly marginated with heterogeneous enhancement is unlikely to be a simple benign adrenal cortical adenoma, and other entities must be considered.

CT examination without intravenously administered contrast material

Findings from multiple studies confirm that an attenuation of 10 HU or less is diagnostic of adrenal cortical adenoma with 79% sensitivity and 96% specificity. With a threshold of 0 HU, the diagnosis may be made with 47% sensitivity and 100% specificity. The decision about how to measure attenuation should be made carefully. The selected region of interest should be as large as possible without including adjacent tissues, particularly periadrenal fat.

CT examination with intravenously administered contrast material

The initial enhancement patterns of adrenal cortical adenomas and adrenal metastases overlap substantially; therefore, simple attenuation measurements are not useful in distinguishing between the two. A delayed attenuation measurement (obtained 10 minutes after the injection) of 30 HU or less is diagnostic of benign adenoma, but only a small percentage of adrenal adenomas have this finding.

A calculation termed contrast-agent washout can be used to reliably determine if an adrenal mass is benign or malignant. Washout is calculated as follows:

1. Intravenous contrast agent is administered, and a scan is obtained after an 80-second delay.
2. A subsequent scan is obtained after a 10-minute delay.
3. A region of interest is drawn over the adrenal mass, and the attenuation is measured in Hounsfield units at 80 seconds and at 10 minutes.
4. The percentage of contrast agent washout is equal to [1 – (attenuation at 10 minutes/attenuation at 80 seconds)] X 100, where the attenuations are in Hounsfield units.

Washout is a measurement of the percentage decrease between the initial enhancement and the delayed enhancement. A large decrease is a high-percentage washout, and a small decrease is a low-percentage washout. If delayed enhancement is exactly half of the initial enhancement, the washout is exactly 50%.

In a series of 101 adrenal masses,¹³ a washout of greater than 50% was specific for benign adrenal adenoma, and a washout of less than 50% was specific for metastasis. Interestingly, these findings are not correlated with the percentage of intracytoplasmic lipid, and the physiologic mechanism resulting in this distinction is not well understood. With a threshold of 50%, use of the washout value yields 98% sensitivity and 100% specificity.

In this series, the 2 missed lesions were benign adenomas that had washouts of 0% and 40%. Both lesions had values of less than 30 HU on delayed images and were correctly diagnosed as benign adrenal cortical adenomas without use of the washout criteria. If the 2 lesions are excluded from the series, the accuracy for this method is 100%. Additional larger series are needed to confirm these striking findings. It is important to remember that benign lesions such as adrenal hematomas or pseudocysts do not enhance with the intravenous administration of contrast material; therefore, these lesions do not have a washout value.

Studies comparing CT histogram analysis with mean CT attenuation analysis for the evaluation of adrenal nodules have found that histogram analysis has greater sensitivity for diagnosis of adenoma.^3,4 In a study of lipid-poor adenomas on unenhanced CT, Ho et al found that although both methods have 100% specificity, using a threshold of more than 10% negative pixels yielded a sensitivity of 84%, compared with 68% for a mean attenuation threshold of less than 10 H.³

Magnetic Resonance Imaging

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 in Multimedia.)

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 in Multimedia.)

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.

Findings

CT and MRI are the modalities of choice in diagnosing adrenal cortical adenoma.

On MRIs, adrenal cortical adenomas are well-circumscribed mass lesions that have homogeneous signal intensity and enhancement patterns. For small lesions (<1.5 cm), thin 5-mm sections should be used to ensure that signal intensity measurements are not affected by volume averaging.

T1-weighted and T2-weighted signal intensity characteristics of benign adrenal adenomas and adrenal metastases are not specific and overlap significantly. However, in-phase and out-of-phase imaging (eg, chemical shift imaging) can be used to diagnose adrenal cortical adenomas with 81-100% sensitivity and 94-100% specificity. Out-of-phase chemical shift images of lipid-rich adrenal adenomas show a decrease in signal intensity. The signal intensity from the spleen can be used as a reference, and ensuring identical preimaging values with both sequences is important. A decrease of 20% in the signal intensity on out-of-phase images relative to that on in-phase images is diagnostic. The signal intensity from liver should not be used as a reference because it may contain lipid.

Results of 2 series show that the percentage decrease in signal intensity on chemical shift images is directly proportional to the amount of intracytoplasmic lipid.¹⁴ Therefore, MRI findings are unlikely to be diagnostic if an adrenal mass has values greater than 30 HU on nonenhanced CT scans.

The visual inspection of signal intensity loss on out-of-phase images is as effective as signal intensity measurements. One important technical point is that the echo time used for out-of-phase imaging should be shorter than that used for in-phase imaging, so that signal intensity loss reflects the presence of lipid and not T2 decay.

MRI cannot be used to definitively characterize lipid-poor adenomas. Although Krestin et al previously described washout with MRI,⁵ the calculations are much more cumbersome to perform than with CT washout in the diagnosis of a lipid-poor adenoma.

A metastatic adrenal lesion located in or adjacent to an adrenal adenoma has been referred to as a collision tumor. One case report documents the MRI features of a benign adrenal cortical adenoma with concomitant adrenal hemorrhage that mimicked a collision tumor.⁶

Ultrasonography

Findings

Ultrasonography of the adrenal glands may be performed to evaluate abdominal masses in infants and children. No ultrasonographic finding is specific for adrenal adenoma. Note that adrenal adenomas are rare in children, accounting for less than 1% of all neoplasms in this population. Adrenal adenomas are much less common than neuroblastomas but slightly more common than pheochromocytomas in children. As a rule, functional adenomas appear earlier than nonfunctional adenomas, and compared with benign adrenal cortical adenoma, adrenal adenocarcinoma is more likely to be functional.

Nuclear Imaging

Findings

Preliminary studies have shown the promise of PET in differentiating adenomas from malignant processes in the adrenal gland. Malignant neoplasms tend to have an increased uptake of fluorine-18-fluorodeoxyglucose relative to benign masses. Because this test does not depend on the presence of lipid, it can potentially be used to characterize both lipid-rich and lipid-poor adenomas. The use of whole-body PET, especially in staging lung cancer, will probably decrease the number of adrenal biopsies performed to assess indeterminate lesions.

Iodomethyl-19-norcholesterol (NP-59) is an investigational radiopharmaceutical that is taken up by adrenal cortical tissue. A Japanese study found that the norcholesterol uptake rate was more sensitive than the CT attenuation value and MR suppression index (96%, 79%, and 67%, respectively) for functioning adrenal adenomas of ³2.0 cm.⁷ In the United States, NP-59 scintigraphy is currently the subject of an active clinical trial.¹⁵

Angiography

Findings

No angiographic findings specific for adrenal adenoma have been identified.

Endovascular adrenal vein sampling can be useful in distinguishing bilateral adrenal hyperplasia from a unilateral functional aldosteronoma.¹⁶

Intervention

Percutaneous adrenal core-needle biopsy, a technically challenging procedure, is used in 85% of patients to obtain an adequate specimen for analysis. The procedure has a 3% rate of complications, which include pneumothorax and hemorrhage.

Biopsy of the left adrenal gland with an anterior approach may lead to pancreatitis.

The histologic and cytologic results from needle biopsy samples of the adrenal gland are reliable in differentiating metastatic lesions from adenomas. However, they are less useful in distinguishing between adrenal adenoma and adrenal adenocarcinoma.

Multimedia

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 in Multimedia.)

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 in Multimedia.)

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 in Multimedia.)

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 in Multimedia.)

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 in Multimedia.)

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 in Multimedia.)

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 in Multimedia.)

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 in Multimedia.)

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.

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.

References

1. Bovio S, Cataldi A, Reimondo G, Sperone P, Novello S, Berruti A, et al. Prevalence of adrenal incidentaloma in a contemporary computerized tomography series. J Endocrinol Invest. Apr 2006;29(4):298-302. [Medline].

2. Boland GW, Lee MJ, Gazelle GS, Halpern EF, McNicholas MM, Mueller PR. Characterization of adrenal masses using unenhanced CT: an analysis of the CT literature. AJR Am J Roentgenol. Jul 1998;171(1):201-4. [Medline].

3. Ho LM, Paulson EK, Brady MJ, Wong TZ, Schindera ST. Lipid-poor adenomas on unenhanced CT: does histogram analysis increase sensitivity compared with a mean attenuation threshold?. AJR Am J Roentgenol. Jul 2008;191(1):234-8. [Medline].

4. Halefoglu AM, Bas N, Yasar A, Basak M. Differentiation of adrenal adenomas from nonadenomas using CT histogram analysis method: A prospective study. Eur J Radiol. Jan 21 2009;[Medline].

5. Krestin GP, Steinbrich W, Friedmann G. Adrenal masses: evaluation with fast gradient-echo MR imaging and Gd-DTPA-enhanced dynamic studies. Radiology. Jun 1989;171(3):675-80. [Medline].

6. Khati NJ, Javitt MC, Schwartz AM. Adrenal adenoma and hematoma mimicking a collision tumor at MR imaging. Radiographics. Jan-Feb 1999;19(1):235-9. [Medline].

7. Yoh T, Hosono M, Komeya Y, Im SW, Ashikaga R, Shimono T, et al. Quantitative evaluation of norcholesterol scintigraphy, CT attenuation value, and chemical-shift MR imaging for characterizing adrenal adenomas. Ann Nucl Med. Jul 2008;22(6):513-9. [Medline].

8. Korobkin M. CT characterization of adrenal masses: the time has come. Radiology. Dec 2000;217(3):629-32. [Medline].

9. Liang HL, Pan HB, Lee YH, et al. Small functional adrenal cortical adenoma: treatment with CT-guided percutaneous acetic acid injection--report of three cases. Radiology. Nov 1999;213(2):612-5. [Medline].

10. Mayo-Smith WW, Boland GW, Noto RB, Lee MJ. State-of-the-art adrenal imaging. Radiographics. Jul-Aug 2001;21(4):995-1012. [Medline].

11. Otal P, Escourrou G, Mazerolles C, et al. Imaging features of uncommon adrenal masses with histopathologic correlation. Radiographics. May-Jun 1999;19(3):569-81. [Medline].

12. Boland GW, Blake MA, Hahn PF, Mayo-Smith WW. Incidental adrenal lesions: principles, techniques, and algorithms for imaging characterization. Radiology. Dec 2008;249(3):756-75. [Medline].

13. Pena CS, Boland GW, Hahn PF, et al. Characterization of indeterminate (lipid-poor) adrenal masses: use of washout characteristics at contrast-enhanced CT. Radiology. Dec 2000;217(3):798-802. [Medline].

14. Hood MN, Ho VB, Smirniotopoulos JG, Szumowski J. Chemical shift: the artifact and clinical tool revisited. Radiographics. Mar-Apr 1999;19(2):357-71. [Medline].

15. Clinical Trials (PDQ®). Adrenal Scans With Radioiodine-Labeled Norcholesterol (NP-59). National Cancer Institute. Available at http://www.cancer.gov/search/ViewClinicalTrials.aspx?cdrid=585137&version=HealthProfessional&protocolsearchid=5407345#ContactInfo_CDR0000585137. Accessed November 10, 2008.

16. Doppman JL, Gill JR Jr. Hyperaldosteronism: sampling the adrenal veins. Radiology. Feb 1996;198(2):309-12. [Medline].

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18. Mittelstaedt CA. Abdominal Ultrasound. 5th ed. 1989.

19. Newhouse JH, Heffess CS, Wagner BJ, et al. Large degenerated adrenal adenomas: radiologic-pathologic correlation. Radiology. Feb 1999;210(2):385-91. [Medline].

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Keywords

adrenal adenoma, adrenal cortical nodular hyperplasia, adrenal tumor, adrenal gland tumor, benign adrenal tumor, adrenal cortical adenoma

Contributor Information and Disclosures

Author

Perry J Horwich, MD, Staff Physician, Instructor of Radiology, Department of Radiology, Beth Israel - Deaconess Medical Center
Perry J Horwich, MD 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
Disclosure: Nothing to disclose.

Coauthor(s)

Stephen A Okon, MD, Consulting Staff, Assistant Professor of Radiology, Department of Radiology, Beth Israel Medical Center
Stephen A Okon, MD is a member of the following medical societies: American Medical Association and American Roentgen Ray Society
Disclosure: Nothing to disclose.

Medical Editor

Glenn Krinsky, MD, Chief of Abdominal Imaging Section, Associate Professor, Department of Radiology, New York University School of Medicine
Glenn Krinsky, MD is a member of the following medical societies: Alpha Omega Alpha and Radiological Society of North America
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

Arnold C Friedman, MD, FACR, Associate Chairman, Department of Radiology, University of Florida Health Science Center; Chief, Department of Radiology, Shands-Jacksonville Hospital
Arnold C Friedman, MD, FACR is a member of the following medical societies: American College of Radiology, American Institute of Ultrasound in Medicine, American Roentgen Ray Society, Association of University Radiologists, and Radiological Society of North America
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Consulting Staff, Department of Radiology, Resolution Imaging Medical Corporation
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

Eugene C Lin, MD, Consulting Radiologist, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of Washington School of Medicine
Eugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine, American College of Radiology, Radiological Society of North America, and Society of Nuclear Medicine
Disclosure: Nothing to disclose.

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Clinical guidelines

ACR Appropriateness Criteria® incidentally discovered adrenal mass. American College of Radiology - Medical Specialty Society.  2000 (revised 2007).  8 pages.  NGC:005995

Stereotactic radiosurgery for patients with pituitary adenomas. IRSA - Professional Association.  2004 Apr.  12 pages.  NGC:003598

Clinical trials

Study of Adrenal Gland Tumors

Adrenal Scans With Radioiodine-Labeled Norcholesterol (NP-59)

Adrenal Tumors - Pathogenesis and Therapy

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