Characterization of adrenal tumors by chemical shift fast low-angle shot MR imaging: comparison of four methods of quantitative evaluation

Adrenal hemangioma-adenoma: an exceedingly rare adrenal collision tumor

Adrenal collision tumors are rare clinical entities referring to separate coexisting adjacent tumors involving an adrenal gland with sharp demarcation between the two and without a substantial histologic admixture at the interface. We report a case of a 60-year-old female patient with an exceedingly rare adrenal hemangioma-adenoma collision tumor. To our knowledge, this is the first report of a collision tumor comprising an adrenal hemangioma and an adenoma.

Diagnostic utility of diffusion-weighted MR imaging and apparent diffusion coefficient value for the diagnosis of adrenal tumors

PURPOSE

To determine the utility of diffusion-weighted MR imaging (DWI) for the diagnosis of adrenal tumors.

MATERIALS AND METHODS

Forty-two patients (24 men and 18 women; age, 61.5 +/- 12.7 years old; range, 34-86 years) with 43 adrenal tumors (11 functioning cortical adenomas, 20 nonfunctioning cortical adenomas, 7 metastatic tumors, and 5 pheochromocytomas) were retrospectively investigated. DWIs were obtained by single-shot spin-echo type echo-planar imaging sequence (1.5 Tesla [T]; TR = 8000 ms, TE = 72, b-factor = 0 and 1000 s/mm(2)), and apparent diffusion coefficient (ADC) value was calculated. Chemical shift images were obtained by gradient echo sequence (TR = 161, TE = 2.38 [out-of-phase, OP] and 4.76 [in-phase, IP], FA = 60), and the signal intensity index (SII; [IP-OP]/IP *100%) was calculated.

RESULTS

There was no difference in ADC values between adenomas (1.09 +/- 0.29*10(-3) mm(2)/s; range, 0.52-1.64) and metastatic tumors (0.85 +/- 0.26*10(-3); 0.51-1.23; p = 0.14). Pheochromocytomas showed the higher mean ADC value (1.59 +/- 0.34*10(-3); 1.04-1.96) compared with those of adenomas or metastatic tumors (P < 0.05 and P < 0.005, respectively). The mean SII of adenomas (62.1 +/- 17.9%; 14.5-88.4) was significantly higher than those of pheochromocytomas (4.0 +/- 10.0%; -19.6-3.3; P < 0.005) or metastatic tumors (-1.5 +/- 11.7%; -18.3-8.2; P < 0.01). There was no correlation between ADC values and SII.

CONCLUSION

Although pheochromocytomas showed higher ADC values, we did not find that ADC value had diagnostic utility for differentiating adenomas and metastatic tumors.

Incidental adrenal lesions: principles, techniques, and algorithms for imaging characterization

Incidental adrenal lesions are commonly detected at computed tomography, and lesion characterization is critical, particularly in the oncologic patient. Imaging tests have been developed that can accurately differentiate these lesions by using a variety of principles and techniques, and each is discussed in turn. An imaging algorithm is provided to guide radiologists toward the appropriate test to make the correct diagnosis.

Quantitative evaluation of norcholesterol scintigraphy, CT attenuation value, and chemical-shift MR imaging for characterizing adrenal adenomas

OBJECTIVE

The objective of our study was to evaluate diagnostic ability and features of quantitative indices of three modalities: uptake rate on norcholesterol scintigraphy, computed tomography (CT) attenuation value, and fat suppression on chemical-shift magnetic resonance imaging (MRI) for characterizing adrenal adenomas.

METHODS

Image findings of norcholesterol scintigraphy, CT, and MRI were reviewed for 78 patients with functioning (n = 48) or nonfunctioning (n = 30) adrenal masses. The norcholesterol uptake rate, attenuation value on unenhanced CT, and suppression on in-phase to opposed-phase MRI were measured for adrenal masses.

RESULTS

The norcholesterol uptake rate, CT attenuation value, and MR suppression index showed the sensitivity of 60%, 82%, and 100%, respectively, for functioning adenomas of <2.0 cm, and 96%, 79%, and 67%, respectively, for those of >or=2.0 cm. A statistically significant correlation was observed between size and norcholesterol uptake, and between CT attenuation value and MR suppression index. Regarding norcholesterol uptake, the adenoma-to-contralateral gland ratio was significantly higher in cortisol releasing than in aldosterone-releasing adenomas.

CONCLUSIONS

The norcholesterol uptake rate was reliable for characterization of adenomas among adrenal masses of >or=2.0 cm. CT attenuation value and MR suppression index were well correlated with each other, and were useful regardless of mass size.

Adrenal phaeochromocytoma: correlation of MRI appearances with histology and function

The purpose of this study was to describe the range of appearances of adrenal phaeochromocytomas on T2-weighted MRI, correlate appearances with histopathology, and quantify the incidence of the previously described hyperintense appearance. The appearance and MR characteristics of 44 phaeochromocytomas were reviewed retrospectively. T2-weighted appearances were grouped: (1) 'classical', homogeneous, high signal intensity, isointense to CSF; (2) homogeneous, isointense or minimally hyperintense to spleen, hypointense to CSF; (3) heterogeneous, marbled appearance; (4) heterogeneous, multiple high signal intensity pockets. All 44 adrenal phaeochromocytomas were well circumscribed, 1.2-15 cm in maximum diameter, with no visual or quantitative signal loss on chemical shift imaging. On T2-weighted MRI 5/44 (11%) had group 1 appearance; 15/44 (34%) group 2, 7/44 (16%) group 3; and 17/44 (39%) group 4. Homogeneous group 1 and 2 lesions were smaller (mean 4.5 cm) than heterogeneous group 3 and 4 lesions (mean 6.3 cm). Increasing MRI heterogeneity correlated pathologically with increasing amounts of haemorrhage, necrosis and fibrosis. No MRI features were predictive of malignancy. Non-functioning phaeochromocytomas were larger than functioning lesions. No size difference was seen between syndrome and sporadic lesions. In this large series we report a wide range of appearances of adrenal phaeochromocytomas on T2-weighted MRI. The previously described classical hyperintense phaeochromocytoma is relatively uncommon.

Effect of echo time pair selection on quantitative analysis for adrenal tumor characterization with in-phase and opposed-phase MR imaging: initial experience

PURPOSE

To determine the effect of two pairs of echo times (TEs) for in-phase (IP) and opposed-phase (OP) 3.0-T magnetic resonance (MR) imaging on (a) quantitative analysis prospectively in a phantom study and (b) diagnostic accuracy retrospectively in a clinical study of adrenal tumors, with use of various reference standards in the clinical study.

MATERIALS AND METHODS

A fat-saline phantom was used to perform IP and OP 3.0-T MR imaging for various fat fractions. The institutional review board approved this HIPAA-compliant study, with waiver of informed consent. Single-breath-hold IP and OP 3.0-T MR images in 21 patients (14 women, seven men; mean age, 63 years) with 23 adrenal tumors (16 adenomas, six metastases, one adrenocortical carcinoma) were reviewed. The MR protocol involved two acquisition schemes: In scheme A, the first OP echo (approximately 1.5-msec TE) and the second IP echo (approximately 4.9-msec TE) were acquired. In scheme B, the first IP echo (approximately 2.4-msec TE) and the third OP echo (approximately 5.8-msec TE) were acquired. Quantitative analysis was performed, and analysis of variance was used to test for differences between adenomas and nonadenomas.

RESULTS

In the phantom study, scheme B did not enable discrimination among voxels that had small amounts of fat. In the clinical study, no overlap in signal intensity (SI) index values between adenomas and nonadenomas was seen (P < .05) with scheme A. However, with scheme B, no overlap in the adrenal gland SI-to-liver SI ratio between adenomas and nonadenomas was seen (P < .05). With scheme B, no overlap in adrenal gland SI index-to-liver SI index ratio between adenomas and nonadenomas was seen (P < .05).

CONCLUSION

This initial experience indicates SI index is the most reliable parameter for characterization of adrenal tumors with 3.0-T MR imaging when obtaining OP echo before IP echo. When acquiring IP echo before OP echo, however, nonadenomas can be mistaken as adenomas with use of the SI index value.

ACR Appropriateness Criteria on incidentally discovered adrenal mass

For patients without a history of malignancy, most small (less than 3 cm) incidentally discovered adrenal masses are benign, and extensive and costly workup is usually not justified. For incidentalomas from 3 to 5 cm in size, computed tomography, magnetic resonance imaging, 2-[(18)F]fluoro-2-deoxyglucose positron emission tomography, adrenal biopsy, or surgery can be considered. Lesions larger than 5 cm should be removed because of the higher risk for malignancy. For patients with histories of malignancy, incidentally discovered adrenal masses are more often malignant, and thus even smaller adrenal lesions are suspect. Adrenal biopsy should be reserved for cases in which the results of noninvasive techniques are equivocal.

MR Imaging of the Adrenal Glands: 1.5T versus 3T

MR imaging at 1.5T is considered the prime cross-sectional imaging modality for characterization of adrenal lesions. This is of utmost clinical importance, because non-functioning adenoma and adrenal metastasis are fairly common. The differentiation of these two tumor entities primarily is based on chemical shift imaging, also known as dual echo in-phase and opposed-phase imaging. At 3.0 T, the echo time pairs for in-phase and opposed-phase MR imaging need to be adjusted because the frequency difference is double that of standard 1.5T MR systems. Unfortunately, the acquisition of the first opposed-phase echo at 1.1 milliseconds and the first in-phase echo at 2.2 milliseconds within the same breath-hold requires unacceptably high receiver bandwidths at 3.0 T. Therefore, alternative data collection schemes have been implemented. This article reviews the current literature regarding adrenal imaging at 3.0 T with a focus on the chemical shift technique.

Comparison of Delayed Enhanced CT and Chemical Shift MR for Evaluating Hyperattenuating Incidental Adrenal Masses1

PURPOSE

To retrospectively compare the accuracy of delayed enhanced computed tomography (CT) and chemical shift magnetic resonance (MR) imaging for characterizing hyperattenuating adrenal masses at CT, with either follow-up imaging or pathologic review as the reference standard.

MATERIALS AND METHODS

The institutional review board approved this retrospective study with a waiver of patient informed consent. Forty-three hyperattenuating adrenal masses (>10 HU) on unenhanced CT images were found in 34 patients (23 men and 11 women; mean age, 52.7 years) by reviewing radiologic reports. These lesions were retrospectively analyzed with delayed enhanced CT and chemical shift MR. The diagnostic accuracy of CT by using absolute percentage loss of enhancement (PLE) and relative PLE and of chemical shift MR by using adrenal-to-spleen ratio (ASR) or signal intensity index (SII) were obtained to determine which modality was more accurate for lipid-poor adenoma. For CT, an adenoma was diagnosed if a mass had an absolute PLE greater than 60% and a relative PLE greater than 40%. For MR, an adenoma was diagnosed if a mass had an ASR of 0.71 or an SII greater than 16.5%. McNemar test was used to compare diagnostic performance of CT and MR.

RESULTS

Hyperattenuating adrenal masses included 37 adenomas and six nonadenomas. The sensitivity, specificity, and accuracy for adenoma at CT were 97% (36 of 37), 100% (six of six), and 98% (42 of 43), respectively, and at MR were 86% (32 of 37), 50% (three of six), and 49% (21 of 43), respectively. CT helped confirm five more adenomas and three more metastatic tumors than did MR. However, there was no significant difference for diagnostic accuracy between these two imaging modalities (P>.05)

CONCLUSION

Delayed enhanced CT can characterize additional hyperattenuating adrenal masses that cannot be characterized with chemical shift MR.

Dynamic contrast enhanced MRI in the differential diagnosis of adrenal adenomas and malignant adrenal masses

OBJECTIVE

To evaluate the value of dynamic MR imaging in the differential diagnosis of adrenal adenomas and malignant tumors, especially in cases with atypical adenomas.

MATERIALS AND METHODS

Sixty-four masses (48 adenomas, 16 malignant tumors) were included in this prospective study. Signal loss of masses was evaluated using chemical shift MR imaging. Five dynamic series of T1-weighted spoiled gradient echo (FFE) images were obtained, with the acquisition starting simultaneously with i.v. contrast administration (0-100 s) followed by a T1-weighted FFE sequence in the late phase (5th minute). Contrast enhancement patterns in the early (25th second) and late (5th minute) phase images were evaluated. For the quantitative evaluation, signal intensity (SI)-time curves were obtained according to the SIs on the 0th, 25th, 50th 75th and 100th second. Also, the wash-in rate, maximum relative enhancement, time-to-peak, and wash-out of contrast at 100 s of masses in both groups were calculated. The statistical significance was determined by Mann-Whitney U test. To evaluate the diagnostic performance of the quantitative tests, receiver operating characteristic (ROC) analysis was performed.

RESULTS

Chemical shift MR imaging was able to differentiate 44 out of 48 adenomas (91.7%) from non-adenomas. The 4 adenomas (8.3%) which could not be differentiated from non-adenomas by this technique did not exhibit signal loss on out-of-phase images. With a cut-off value of 30, SI indices of adenomas had a sensitivity of 93.8%, specificity of 100% and a positive predictive value of 100%. On visual evaluation of dynamic MR imaging, early phase contrast enhancement patterns were homogeneous in 75% and punctate in 20,83% of the adenomas; while patchy in 56.25% and peripheral in 25% of the malignant tumors. On the late phase images 58.33% of the adenomas showed peripheral ring-shaped enhancement and 10.41% showed heterogeneous enhancement. All of the malignant masses showed heterogeneous enhancement. At the 25th second, the SIs and wash-in rates of the adenomas were significantly higher than those of the malignant masses (p=0.010). Time-to-peak enhancement of the malignant masses was significantly longer than that of the adenomas. With a cut-off value of 52.85 s, the time-to-peak enhancement had 87.5% sensitivity and 80% specificity.

CONCLUSION

Chemical shift MR has a high sensitivity and specificity in the differential diagnosis of adenomas and malignant adrenal masses. However, taking into consideration only the atypical adenomas, chemical shift MRI is of no diagnostic value. Although the diagnostic value of dynamic MRI is lower than chemical shift MRI, in the atypical cases contrast enhancement patterns and time-to-peak and wash-in rates derived from SI-time curve of dynamic MRI give are contributory to the results of chemical shift MRI.

Integrated PET-CT for the characterization of adrenal gland lesions in cancer patients: diagnostic efficacy and interpretation pitfalls

Integrated fluorine-18 fluorodeoxyglucose positron emission tomography (PET)-computed tomography (CT) for adrenal gland imaging in cancer patients allows early detection and accurate localization of adrenal lesions and differentiation of metastatic nodules from benign lesions, thereby facilitating treatment planning. However, false-positive findings are encountered at integrated PET-CT in approximately 5% of adrenal lesions identified as positive at PET, including adrenal adenomas, adrenal endothelial cysts, and inflammatory and infectious lesions. Moreover, false-negative findings may be seen in adrenal metastatic lesions with hemorrhage or necrosis, small-sized (<10-mm) metastatic nodules, and metastases from pulmonary bronchioloalveolar carcinoma or carcinoid tumors. An awareness of the potential pitfalls of integrated PET-CT enhances the diagnostic efficacy of this modality by allowing differentiation of metastatic adrenal lesions from other abnormalities.

The pancreas in beta-thalassemia major: MR imaging features and correlation with iron stores and glucose disturbances

The study aims at describing the MR features of pancreas in beta-thalassemia major, investigating the relations between MR findings and glucose disturbances and between hepatic and pancreatic siderosis. Signal intensity ratios of the pancreas and liver to right paraspinous muscle (P/M, L/M) were retrospectively assessed on abdominal MR imaging studies of 31 transfusion-dependent patients with beta-thalassemia major undergoing quantification of hepatic siderosis and 10 healthy controls, using T1- (120/4/90), intermediate in and out of phase - (120/2.7, 4/20), and T2*-(120/15/20) weighted GRE sequences. Using the signal drop of the liver and pancreas on opposed phase images, we recorded serum ferritin and results of oral glucose tolerance test (OGTT). Decreased L/M and P/M on at least the T2* sequence were noticed in 31/31 and 30/31 patients, respectively, but no correlation between P/M and L/M was found. Patients with pathologic OGTT displayed a higher degree of hepatic siderosis (p < 0.04) and signal drop of pancreas on opposed phase imaging (p < 0.025), implying fatty replacement of pancreas. P/M was neither correlated with glucose disturbances nor serum ferritin. Iron deposition in the pancreas cannot be predicted by the degree of hepatic siderosis in beta-thalassemia major. Fatty replacement of the pancreas is common and may be associated with glucose disturbances.

Value of chemical shift subtraction MRI in characterization of adrenal masses

OBJECTIVE

The purpose of this study was to assess the advantages of the image subtraction technique in chemical shift MRI for the differentiation of adrenal adenomas from nonadenomas.

SUBJECTS AND METHODS

Thirty-five patients with 42 adrenal masses (eight metastases and 34 nonfunctioning adenomas) underwent chemical shift MRI using a double-echo fast low-angle shot sequence. Subsequently, opposed-phase chemical shift MR images were subtracted from in-phase images. The subtraction images were assessed quantitatively and qualitatively. For quantitative assessment, the signal intensity values of the adrenal masses were measured by one investigator with manually defined regions of interest. Qualitative assessment of the subtraction images was performed independently by two investigators, who reported their confidence in diagnosing adenomas versus nonadenomas based on signal intensity of the adrenal masses on subtraction images.

RESULTS

The mean signal intensities were significantly different between adenomas and metastases on subtraction images (213 vs 18; p < 0.0001). There was no overlap in signal intensities between adenomas and metastatic tumors. The accuracy in distinguishing adenomas from metastatic tumors was 100% if the cutoff value of the signal intensity selected was 36-106. Quantitative results corresponding to 100% specificity were also observed, with similar sensitivity. No difference in interpretation between the two investigators occurred.

CONCLUSION

Chemical shift subtraction MRI provides a high confidence level in distinguishing adrenal adenomas from adrenal metastases. The image subtraction technique also facilitates quantitative and qualitative evaluation of adrenal masses in chemical shift MRI.

Hepatic fat fraction: MR imaging for quantitative measurement and display--early experience

The institutional review board approved this HIPAA-compliant study. After all five patients with nonalcoholic fatty liver disease signed a consent, they underwent magnetic resonance (MR) imaging for hepatic fat quantification. The purpose of this study was to develop a fast and accurate method to acquire and display quantitative maps of the percentage of hepatic fat. In-phase and out-of-phase gradient-echo MR imaging was performed with dual flip angles (70 degrees, 20 degrees) to resolve ambiguity of the dominant constituent. T2* corrections were also estimated and applied to generate color-coded maps of the estimated percentage of hepatic fat. MR imaging results were compared with biopsy results in two of five patients, and the technique was validated qualitatively and quantitatively with a water-oil phantom. Results of the phantom study confirmed that the dual-flip angle algorithm can be used to correctly identify the dominant constituent, allowing depiction of 0%-100% of fat content. The estimated liver fat fraction was comparable to quantitative fat measurements at biopsy in both patients (MR imaging, 18.3% +/- 2.8 [standard deviation] and 28.6% +/- 2.4, vs quantitative histopathologic analysis, 11.2% and 28.5%, respectively).

SUPPLEMENTAL MATERIAL

radiology.rsnajnls.org/cgi/content/full/2373041639/DC1

Non-invasive evaluation of the incidentally detected indeterminate adrenal mass

Clinically silent adrenal masses are discovered incidentally during diagnostic testing or treatment for clinical conditions that are not related to suspicion of adrenal disease; thus, they are commonly referred to as 'incidentalomas'. The widespread use of high-resolution anatomic imaging techniques such as computed tomography (CT) and magnetic resonance (MR) imaging has led to the increased detection of these masses. In many patients without a known extra-adrenal primary malignancy--and even in patients with a primary neoplasm--most adrenal masses ultimately prove to be benign. However, it remains important that these adrenal masses are accurately characterized to exclude the treatable causes of adrenal disease, and also to accurately stage the oncology patient. The purpose of this chapter is to describe the findings and recent advances in non-invasive imaging methods that are now available for the accurate characterization of incidentally detected adrenal masses (i.e. the differentiation of benign from malignant masses). The imaging techniques and the algorithms that are used in our institution for the evaluation of incidentally detected adrenal mass will be described.

Imaging functional adrenal disorders

Technological developments in cross-sectional imaging have revolutionized the localization and characterization of functioning adrenal pathology. With effective use of modern imaging, the diagnosis of the cause and nature of functioning adrenal pathology can be reached speedily, accurately and efficiently in the majority of patients. We review the appearance of primary and secondary adrenal pathology, evaluate the diagnostic performance of imaging modalities, highlight newer technical developments, and propose a rational use of these tests in identifying functioning adrenal disease.

Importance of adrenal incidentaloma in patients with a history of malignancy

BACKGROUND

Adrenal incidentaloma presents a frequent finding in patients with a history of malignancy. This study was carried out to determine whether imaging techniques can discriminate between a malignant and a benign adrenal tumor and subsequently select candidates for adrenal surgery.

METHODS

Beginning in July 1995, oncologic patients with adrenal incidentaloma underwent abdominal ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), and [ 18 ]fluoro-2-deoxy-D-glucose positron emission tomography (18-FDG-PET). Consecutively in all patients adrenalectomy was performed. Histologic findings were compared with the imaging results.

RESULTS

In 42 patients, 33 to 79 years old (mean age, 58 years), 44 adrenal lesions were detectable. Two patients presented with bilateral adrenal masses. At operation, 43 adrenal resections and 3 biopsies were performed. Histologic examination revealed 31 metastases (71%) and 13 adrenal adenomas (29%). In metastases the sensitivity of ultrasonography, CT, MRI, and 18-FDG-PET was 66%, 81%, 100%, and 100%, respectively. For adrenal adenoma, the sensitivity of ultrasonography, CT, MRI, and 18-FDG-PET was 46%, 39%, 100%, and 54%, respectively.

CONCLUSIONS

In oncologic patients with indeterminate adrenal tumors MRI and 18-FDG-PET provide accurate differentiation between metastases and benign adenomas. Positive results of these 2 imaging modalities are highly suggestive for metastatic disease. In cases of negative MRI and 18-FDG-PET results the adrenal lesion corresponds to a benign adenoma that needs no surgical intervention.

MR imaging of the adrenal glands

MR imaging is used commonly for imaging the adrenal glands. Its high-contrast resolution and multiplanar imaging capability enables the detection and characterization of many adrenal masses. The advent of chemical-shift imaging revolutionized the role of MR imaging in characterizing adrenal masses. In this article, the authors discuss the range of MR appearances of common and uncommon adrenal masses, focusing on the nonfunctioning incidentally discovered mass and its characterization methods. MR imaging is continuously improving. The increasing use of higher strength magnets and the introduction of newer coils, sequences, and techniques will help detect and characterize very small adrenal masses, quantify their fat content, and provide exquisite morphologic images of the gland and its vascular supply.

Comparison of Unenhanced CT and Chemical Shift MRI in Evaluating Lipid-Rich Adrenal Adenomas

OBJECTIVE

Our aim was to evaluate adrenal adenomas in patients who underwent both unenhanced CT and chemical shift MRI to determine if adenomas can be characterized with MRI when the findings of CT are indeterminate.

MATERIALS AND METHODS

Between January 1999 and June 2003, 40 patients (42 adrenal masses) underwent unenhanced CT and chemical shift MRI and were retrospectively analyzed. Hounsfield units, adrenal-to-spleen chemical shift ratio, and signal-intensity index were obtained for each adrenal mass. Qualitative analysis for loss of signal in each adrenal mass on the opposed-phase images was also performed by two reviewers and compared with the quantitative analyses. A lipid-rich adenoma was diagnosed if the mass measured equal to or less than 10 H, had an adrenal-to-spleen chemical shift ratio of less than 0.71, and had a signal-intensity index of greater than 16.5% or if the mass fulfilled two of the preceding criteria and had follow-up imaging without change.

RESULTS

The sensitivities and specificities for diagnosing a lipid-rich adenoma using the qualitative, adrenal-to-spleen chemical shift ratio, signal-intensity index, and unenhanced CT attenuation analyses were 92% (33/36) and 17% (1/6), 100% (36/36) and 100% (6/6), 100% (36/36) and 67% (4/6), and 78% (28/36) and 83% (5/6), respectively. Twenty-eight (67%) lipid-rich adenomas measured equal to or less than 10 H, had an adrenal-to-spleen chemical shift ratio of less than 0.71, and had a signal-intensity index of greater than 16.5%. Eight masses (19%) measured greater than 10 H but had an adrenal-to-spleen chemical shift ratio of less than 0.71 and a signal-intensity index greater than 16.5% and were unchanged at follow-up.

CONCLUSION

Eight (62%) of 13 adrenal adenomas measuring greater than 10 H on unenhanced CT were definitively characterized with chemical shift MRI.

The clinically inapparent adrenal mass: update in diagnosis and management

Clinically inapparent adrenal masses are incidentally detected after imaging studies conducted for reasons other than the evaluation of the adrenal glands. They have frequently been referred to as adrenal incidentalomas. In preparation for a National Institutes of Health State-of-the-Science Conference on this topic, extensive literature research, including Medline, BIOSIS, and Embase between 1966 and July 2002, as well as references of published metaanalyses and selected review articles identified more than 5400 citations. Based on 699 articles that were retrieved for further examination, we provide a comprehensive update of the diagnostic and therapeutic approaches focusing on endocrine and radiological features as well as surgical options. In addition, we present recent developments in the discovery of tumor markers, endocrine testing for subclinical disease including autonomous glucocorticoid hypersecretion and silent pheochromocytoma, novel imaging techniques, and minimally invasive surgery. Based on the statements of the conference, the available literature, and ongoing studies, our aim is to provide practical recommendations for the management of this common entity and to highlight areas for future studies and research.