| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Review |
1 Both authors: Department of Radiology, University of Michigan Health System, 1500 E. Medical Center Dr., Ann Arbor, MI 48109-0030.
Received January 11, 2002;
accepted after revision February 26, 2002.
Address correspondence to N. Reed Dunnick.
Introduction
 Top Introduction Specific Imaging FeaturesNonspecific Imaging FeaturesAdenoma Versus MetastasisAdenoma Versus CarcinomaReferences |
|---|
An adrenal mass detected during a CT or MR imaging examination that is being performed for reasons other than suspected adrenal abnormalities is often referred to as an adrenal incidentaloma. The continuing uncertainty about the appropriate clinical and imaging management of adrenal incidentalomas was attested to by the National Institutes of Health consensus conference on this subject on February 4-6, 2002. The purpose of this article is to review the imaging features of nonhyperfunctioning adrenal masses and the recent advances in noninvasive imaging methods to help differentiate benign from malignant lesions. The changing role for percutaneous biopsy of an adrenal mass will also be addressed.
|
TopIntroductionSpecific Imaging FeaturesNonspecific Imaging FeaturesAdenoma Versus MetastasisAdenoma Versus CarcinomaReferences |
|---|
Because of the large amount of mature fat, most myelolipomas are easily recognized on CT (Fig. 1). Elements of a soft-tissue density are found in varying amounts, and calcification is seen in up to 20% of the cases. Occasional myelolipomas have no recognizable fat, which precludes the diagnosis on imaging studies.
|
The appearance of a myelolipoma on MR imaging reflects the proportion of fat and of bone marrow elements in the tumor. Fat has a high signal intensity on both T1- and T2-weighted sequences. The bone marrow elements have a low signal intensity on T1-weighted images and moderate signal intensity on T2-weighted images [5, 6]. Because a diagnosis of myelolipoma can usually be made with confidence using CT or MR imaging, most patients with myelolipoma are treated conservatively. In some cases, distinguishing a large myelolipoma from a retroperitoneal sarcoma may not be possible, and biopsy or surgery may be needed for definitive diagnosis.
Cyst
Adrenal cysts are uncommon lesions, and few reports about their CT
appearance can be found in the literature. Adrenal cysts show a 3:1 female
predilection. Four types of cysts are recognized on the basis of pathologic
classification: endothelial, epithelial, parasitic, and posttraumatic
pseudocysts [7].
The sonographic appearance of an adrenal pseudocyst can be complex, with
multiple internal septations. CT is usually more useful to define the lesion
and assess contrast enhancement. A recent report of 13 new cystic adrenal
masses and review of 26 benign adrenal cysts from the literature included one
cystic adrenal cortical carcinoma
[8]. Of the 37 reviewed benign
cysts, 19 had mural and seven had central calcification, 28 were unilocular,
and seven had high attenuation values. The thickness of the wall of the lesion
was 3 mm or less in 31 lesions. The authors concluded that the CT finding of a
nonenhancing mass with or without wall calcification allows differentiation of
an adrenal cyst from an adenoma (Fig.
2). A small adrenal cyst with near-water attenuation and a thin
(
3 mm) wall is likely to be benign.
|
Hemorrhage
Adrenal hemorrhage can be bilateral or unilateral. When adrenal hemorrhage
is bilateral, the cause is usually associated with anticoagulation therapy or
a blood dyscrasia; less commonly, it is associated with the stress of surgery,
sepsis, or hypotension; and rarely, it is caused by trauma
[9]. Unilateral adrenal
hemorrhage is usually caused by blunt abdominal trauma and involves the right
gland more often than the left
[10]. Adrenal vein thrombosis
may also cause unilateral adrenal hemorrhage. Adrenal vein thrombosis may
result from catheterization performed to collect blood samples from the
adrenal vein in patients with suspected adrenal endocrine disease
[11,
12]. In the absence of
catheterization or blunt trauma, unilateral adrenal hemorrhage may occur into
a preexisting neoplasm, necessitating surgical exploration if follow-up
imaging does not show a nearly normal adrenal gland.
Acute or subacute adrenal hemorrhage typically has an unenhanced attenuation value of 50-90 H (Fig. 3). Follow-up studies show diminution in size of the adrenal mass with a gradual decrease in the attenuation value [13]. The high attenuation value of a recent adrenal hemorrhage is usually readily apparent on unenhanced CT, but is indistinguishable from a solid adrenal neoplasm on contrast-enhanced CT. Detection of an adrenal mass on contrast-enhanced CT after trauma is usually assumed to result from a hematoma, but an unrelated adrenal neoplasm can be excluded only by unenhanced CT or serial follow-up CT. Similarly, MR imaging may indicate hemorrhage by the high signal intensity, which reflects the presence of methemoglobin, on T1-weighted images [14, 15].
|
|
TopIntroductionSpecific Imaging FeaturesNonspecific Imaging FeaturesAdenoma Versus MetastasisAdenoma Versus CarcinomaReferences |
|---|
|
Hemangioma
An adrenal hemangioma is a rare benign tumor. Hemangiosarcomas occur but
are even less common [17].
Hemangiomas are composed of closely adjacent vascular channels lined with a
single layer of endothelium
[18]. These benign tumors do
not produce adrenal hormones, and most are large when found as an incidental
finding.
On CT, hemangiomas are seen as large well-defined masses. They have a soft-tissue density on unenhanced images and exhibit inhomogeneous enhancement. Most hemangiomas are calcified, either from phleboliths in the tumor or from previous hemorrhage [19].
The MR findings associated with hemangiomas include a hypointense appearance relative to the liver on T1-weighted sequences [20]. Central hyperintensity may be seen because of hemorrhage. On T2-weighted images, hemangiomas are hyperintense. Peripheral enhancement that persists on delayed images is characteristic. These tumors are usually removed because of the risk of hemorrhage and inability to exclude malignancy.
Ganglioneuroma
A ganglioneuroma is a benign tumor composed of Schwann cells and ganglion
cells. These lesions occur anywhere along the paravertebral sympathetic
plexus, and approximately 20-30% arise in the adrenal medulla
[21]. Because they do not
secrete hormones, most ganglioneuromas are detected as an incidental finding
[22].
On CT, ganglioneuromas appear as a solid adrenal mass ranging from 4 to 22 cm in diameter [21]. Extraadrenal retroperitoneal tumors may be even larger. The density of the lesion on unenhanced images is often less than that of muscle. Contrast-enhanced images show homogeneous or mildly heterogeneous enhancement.
On MR imaging, the signal intensity of a ganglioneuroma is less than that of liver on T1-weighted sequences. Greater heterogeneity is seen on T2-weighted images than on enhanced CT images. Although the tumor may surround blood vessels, encroachment on the lumen is rare.
Neuroblastoma
Although neuroblastoma is the third most common malignant tumor seen in
children, neuroblastoma is seen less frequently in adults. This tumor may
occur anywhere along the parasympathetic plexus. Adults are more likely to
present with disseminated disease than children
[23].
The imaging findings of neuroblastoma in adults are similar to those in children. The lack of specificity of imaging features and more frequent disseminated involvement make lymphoma or metastatic disease likely possibilities in these patients. Calcification, which is commonly found in children, is less often present in adults.
Pheochromocytoma
Although most patients with pheochromocytoma present with manifestations of
excess catecholamine production, approximately 10% of these tumors are silent
and are detected by other means such as an imaging study
[24,
25]. Approximately 90% of
pheochromocytomas lie within the adrenal glands, although the incidence of
extraadrenal tumors is higher among sporadic pheochromocytomas than those
associated with the multiple endocrine neoplasia syndromes
[26].
On CT, pheochromocytomas appear as a well-defined mass with a density near that of muscle. After IV contrast medium has been administered, marked enhancement can be seen, reflecting the vascularity of the tumors. Larger lesions may be heterogeneous because of tissue necrosis or internal hemorrhage. Non-hyperfunctioning pheochromocytomas tend to be larger than functioning tumors [27].
MR findings may enable characterization of pheochromocytomas because the signal intensity of these tumors is sometimes very high on T2-weighted images [28]. This high signal intensity, which is probably caused by a cystic component [29], may be especially useful for extraadrenal tumors. If present, it can also help distinguish a pheochromocytoma from an adrenal adenoma.
Because manipulation of pheochromocytomas may induce a hypertensive crisis, diagnosis or exclusion of this entity should be achieved as noninvasively as possible. Nonhyperfunctioning pheochromocytomas may still produce an elevated level of catecholamine, although a lower level than that found in a symptomatic patient [27]. Thus, measuring catecholamine levels may be useful for patients with an incidentally discovered adrenal mass.
Radionuclide imaging is recommended for problem cases such as ectopic tumors not found in the abdomen or pelvis or those suspected of recurrent or metastatic disease [30]. Metaiodobenzylguanidine (MIBG) is concentrated in catecholamine storage granules in pheochromocytomas and MIBG labeled with either iodine-123 or iodine-131 has a high sensitivity for detecting pheochromocytomas [31]. Although their experience was limited, a group of researchers found that performing positron emission tomography (PET) after administering FDG enabled them to localize a pheochromocytoma in two patients with false-negative findings on MIBG studies [32].
Adenoma
An adenoma is the most common adrenal tumor. Adenomas are reported to occur
in from 1.4% to 8.7% of postmortem examinations, depending on the criteria
used
[33,34,35].
The incidence is even higher among patients with hypertension or diabetes
mellitus
[34,35,36].
Adenomas large enough to be recognized on survey abdominal CT examinations are
found in approximately 1% of patients, but may be increasingly detected as CT
technology improves [37].
Nonhyperfunctioning adenomas elaborate adrenal cortical hormones the same as other functioning adrenal cortical tissue. Thus, these lesions are seen to take up adrenal cortical labeling radionuclides.
On CT, adenomas may have the same density as normal adrenal tissue. Because most adenomas contain large amounts of intracytoplasmic lipid, many have a low density, often near that of water, on unenhanced examinations [38] (Fig. 5). Calcification is rare. Adenomas enhance after the IV administration of iodinated contrast medium (Fig. 6). Although the degree of enhancement does not significantly differ from that of other adrenal tumors, adenomas show more rapid washout of contrast medium than adrenal metastases [39,40,41].
|
|
The MR signal characteristics of adenomas are also similar to those of normal adrenal tissue. Although the signal intensity of an adenoma tends to be low on T2-weighted sequences, this finding is not useful for differentiating adenomas from metastases because the range of signal intensity of adenomas overlaps 20-30% with metastases. Chemical-shift imaging can be used to identify the intracytoplasmic lipid and can distinguish many adenomas from metastases [42, 43] (Fig. 7A,7B).
|
|
Carcinoma
Adrenal carcinoma is a rare tumor, with a reported incidence of two cases
per million [44]. Patients may
present with abdominal pain, a palpable mass, or with Cushing's syndrome
because approximately 50% of these tumors elaborate unregulated amounts of
cortisol. Many adrenal carcinomas elaborate insufficient amounts of hormone to
produce obvious clinical manifestations. Other endocrine manifestations of
adrenal carcinoma include Conn's syndrome, virilization, and feminization, but
these manifestations are rare. The tumors tend to be very large at
presentation.
The CT appearance of an adrenal carcinoma is that of a large mass. Central necrosis is common, and calcification is seen in 20-30% of the cases [45, 46] (Fig. 8A). Enhancement is heterogeneous after IV administration of contrast medium. Venous extension of tumor into the left renal vein or inferior vena cava is common and can usually be identified on contrast-enhanced images [44] (Fig. 8B). Precisely defining the cephalad extent of the IV tumor is important because this point is where the surgeon can gain vascular control of the tumor [47]. Although defining the cephalad extent of the tumor can often be achieved with CT, MR imaging may be helpful in problematic cases [48].
|
|
On MR imaging, carcinomas are usually heterogeneously hyperintense on both T1- and T2-weighted images, reflecting the frequent internal hemorrhage and central necrosis. Enhancement is also heterogeneous, revealing nodular areas of intense enhancement and other areas with no enhancement. IV extension of tumor is typically depicted well on MR imaging because data sets can be projected into multiple planes [48, 49] (Fig. 9).
|
Lymphoma
Primary lymphoma of the adrenal glands is rare
[50], but secondary
involvement when other retroperitoneal lymphoma is present is seen more
commonly among patients with non-Hodgkin's lymphoma than Hodgkin's disease
[51]. Involvement is often
bilateral and other retroperitoneal disease is usually present.
The CT appearance of adrenal lymphoma may be of discrete masses (tumefactive) or of more diffuse involvement of the gland in which the shape of the gland may be maintained. There may be extensive retroperitoneal tumor that engulfs the adrenal glands, making them difficult to identify. The enhancement of lymphoma after the administration of intravascular contrast medium is less than that of the aorta or inferior vena cava.
On MR imaging, lymphoma has a signal intensity lower than that of the liver on T1-weighted images. Lymphoma is typically heterogeneously hyperintense on T2-weighted sequences.
Metastases
The adrenal glands are a common site of metastatic disease, found in
approximately 27% of the postmortem examinations of patients with malignant
neoplasms of epithelial origin
[52]. The most common
neoplasms with adrenal metastases are carcinomas of the lung and breast and
melanoma [52,
53]. Adrenal metastases can be
unilateral or bilateral, small or large. The CT and MR imaging features are
nonspecific. Small metastases are often homogeneous on contrast-enhanced CT
(Fig. 10) or MR imaging,
whereas large metastases often have local regions that appear heterogenous as
a result of necrosis (Fig.
11A,11B,11C),
hemorrhage, or both. Calcification is rare in adrenal metastases.
|
|
|
|
|
TopIntroductionSpecific Imaging FeaturesNonspecific Imaging FeaturesAdenoma Versus MetastasisAdenoma Versus CarcinomaReferences |
|---|
Evidence has accumulated that unenhanced CT densitometry can be used to accurately differentiate adrenal adenomas from metastases [54,55,56]. Most adenomas have unenhanced CT attenuation values lower than metastases, and the scatterplot data from such studies were used to determine a threshold value that resulted in the calculation of the optimal combination of sensitivity and specificity for the diagnosis of adenoma. In an oncologic patient with an adrenal mass but no other evidence of distant metastatic disease, the goal of noninvasive diagnostic imaging is to characterize the adrenal mass as an adenoma with high specificity. High specificity of the diagnosis is important so that a metastasis is not mistakenly diagnosed as an adenoma, potentially resulting in a fruitless attempt at curative therapy of the primary tumor. In addition, a highly specific diagnosis of adenoma can obviate percutaneous biopsy of most adenomas. High sensitivity for the diagnosis of adrenal adenoma is not as critical, because the only deleterious consequence of an adenoma incorrectly diagnosed as a metastasis is that a percutaneous adrenal biopsy will be necessary to establish the correct diagnosis.
Using pooled data from multiple published studies of calculated accuracies and corresponding threshold values of unenhanced attenuation values, a group of researchers found that the most optimal sensitivity (71%) and specificity (98%) for the diagnosis of adrenal adenoma result from choosing a threshold attenuation value of 10 H on unenhanced CT [56]. There is less than two chances out of 100 that an adrenal mass with an attenuation of less than 10 H on unenhanced CT will not be an adenoma. Unlike unenhanced attenuation values, however, IV contrast—enhanced CT values show too much overlap between adenomas and metastases to allow an accurate differentiation between them [55].
Evidence has accumulated that chemical-shift MR imaging can also be used to differentiate adrenal adenomas from metastases. Taking advantage of the different resonant frequency peaks for the hydrogen atom in water and triglyceride (lipid) molecules, chemical-shift MR imaging results in a decrease in the signal intensity of tissue containing both lipid and water in comparison with tissue containing no lipid [57]. When a breath-hold gradient-echo technique is used, signal intensity loss on opposed-phase images compared with in-phase images indicates a mixture of lipid and nonlipid tissue; this finding is often present in adrenal adenomas but absent in metastases. The chemical-shift change can be detected by simple visual analysis or by quantitative methods using standard region-of-interest cursor measurements of the mass and often of an adjacent reference tissue on in-phase and opposed-phase images. Several different formulas have been proposed to quantify the amount of chemical-shift change and optimal threshold values determined by analysis of scatterplot data [58].
Although some investigators have used these quantitative measurements and formulas to detect the presence of lipid within adrenal adenomas, others have emphasized the advantages of simple visual analysis to detect relative signal intensity loss on opposed-phase images of adrenal adenomas. The ability to subjectively compensate for motion and other artifacts that are superimposed over an adrenal mass and the identification of local rather than diffuse lipid are two of the advantages cited in favor of visual rather than quantitative analysis of chemical-shift changes [59]. Several studies have shown a similar accuracy for detecting intratumoral lipid in adrenal masses using both visual analysis and quantitative methods in the same patients [58, 60]. The most rigorous assessment of visual analysis of in-phase and opposed-phase imaging of adrenal masses showed a sensitivity of 78% for the detection of lipid within adrenal adenomas with a corresponding specificity of 87% [59].
Two studies suggest that unenhanced CT densitometry and chemical-shift MR
imaging both detect the presence and amount of lipid within adrenal adenomas.
In one study of 47 adrenal masses that were imaged with both techniques, the
inverse linear correlation between the CT attenuation value and the amount of
chemical-shift change on MR imaging was good. In addition, six of the
eight
masses that were falsely
negative for adenoma were incorrect on both examinations
[61]. In a study with
histologic—radiologic correlation of a small number of resected adrenal
adenomas that were preoperatively imaged on CT, chemical-shift MR imaging, or
both, there was good inverse linear correlation between the estimated number
of lipidrich cells and the unenhanced CT attenuation value and good linear
correlation with the relative change in signal intensity on opposed-phase MR
imaging [38]. Taken together,
these two studies suggest that unenhanced CT and chemical-shift MR imaging may
not be complementary to each other in the diagnosis of adrenal adenomas, which
may partly explain the paucity of published reports comparing the two
techniques with each other.
|
Standard contrast-enhanced CT images of the adrenal glands are obtained approximately 60 sec after the beginning of IV injection of a contrast bolus. Studies suggest this time point is the only one when the attenuation values of adenomas and metastases are nearly identical. Adenomas lose enhancement more rapidly, as early as 5 min after the injection of contrast material, so attenuation values at 10-15 min after contrast administration can be used to differentiate adenomas from other masses [9, 62] (Figs. 12A,12B,12C and 13). Although the threshold attenuation value for the diagnosis of an adenoma varies among series, masses with an attenuation value of less than 30-40 H on a contrast-enhanced CT scan obtained with a 15-min delay are almost always adenomas.
|
|
|
|
A prior report indicated the more rapid washout of gadolinium enhancement on MR imaging of adrenal adenomas could also differentiate them from metastases [63]. Subsequent reports could not confirm these results, however [60, 64], and dynamic gadolinium-enhanced MR imaging is not widely used for this purpose.
In addition to the delayed CT attenuation value itself, the percentage of washout of initial enhancement—which probably is independent of the type, amount, and injection rate of the contrast material—can be calculated [65, 66]. In our department, the optimal threshold enhancement washout at 15 min is 60%, resulting in a sensitivity of 88% and a specificity of 96% for the diagnosis of adenoma [65]. Of particular interest is the apparent independence of this rapid enhancement washout from the lipid content of an adenoma. Lipid-poor adenomas, those with attenuation values greater than 10 H on unenhanced CT, have enhancement washout features nearly identical to lipid-rich adenomas [67].
The percentage of enhancement washout of an adrenal mass is easy to
calculate using the following equation:
 |
 |
If a the threshold value of 60% is used, then the mass is likely a
lipid-poor adenoma. However, if unenhanced CT has not been performed or if the
unenhanced attenuation value is unknown, a relative enhancement washout can be
calculated as follows:
 |
In our department, the optimal threshold value for the relative enhancement washout calculation is 40%, resulting in a sensitivity of 96% and a specificity of 100% for the diagnosis of adenoma. Another study of the accuracy of using the relative enhancement washout to characterize adrenal masses reported an optimal threshold of 50% [68], resulting in a sensitivity and specificity of 100%.
In the previous example, the calculation for relative enhancement washout
is as follows:
 |
Given the threshold value for relative enhancement washout of 40%, this calculation again indicates an adenoma.
The assessment of enhancement washout curves of adrenal masses is valid only for lesions with relatively homogeneous attenuation after contrast enhancement. Large regions of low attenuation, likely representing areas of necrosis or hemorrhage, were specifically excluded from evaluation in the articles that described and quantified the washout curves. The calculations apply only to solid tissue with an intact capillary bed. The diagnosis of adrenal adenoma cannot be determined in masses that contain prominent regions of necrosis or hemorrhage.
Combining the two independent CT properties of adrenal adenomas—rapid contrast enhancement washout and a propensity for intratumoral lipid—leads to a protocol that spares most adenomas from contrast enhancement. We recently reported the accuracy of combined unenhanced and delayed enhanced CT densitometry for the characterization of adrenal masses [69]. One hundred sixty-six adrenal masses were prospectively studied with unenhanced CT; those with attenuation values greater than 10 H underwent contrast-enhanced CT and contrast-enhanced CT with a 15-min delay. This protocol enabled the correct characterization of 160 (96%) of the 166 masses. When the five nonadenomas that were not metastases were excluded, the sensitivity and specificity for characterizing a mass as adenoma versus metastasis were 98% (124/127) and 97% (33/34), respectively.
Two radionuclide studies can also be used to characterize adrenal masses. Radioiodocholesterol scanning using NP-59 (iodomethylnorcholesterol) is an accurate method to characterize a unilateral adrenal mass as an adenoma because the radionuclide labels functioning adrenal cortical cells even in nonhypersecretory adenomas [70] (Fig. 14A,14B). The high positive predictive value of NP-59 scintigraphy has been known for approximately 20 years, but its lack of approval from the United States Food and Drug Administration and restricted commercial availability have severely limited its widespread use.
|
|
Whole-body FDG PET is the newest imaging modality used to differentiate benign from malignant masses. FDG PET exploits fundamental biochemical differences between normal and neoplastic cells, and unlike the other imaging modalities discussed in this article, an FDG PET study with positive findings typically identifies a malignant mass (adrenal metastasis) rather than an adrenal adenoma (Fig. 14A,14B). Initial reports about the ability of FDG PET to characterize adrenal masses are promising [71, 72], but the small number of reported cases, current high cost of the examination, and the lack of widespread availability of the new modality make it difficult to predict its future role in the evaluation of incidental adrenal masses.
|
TopIntroductionSpecific Imaging FeaturesNonspecific Imaging FeaturesAdenoma Versus MetastasisAdenoma Versus CarcinomaReferences |
|---|
A unilateral adrenal mass larger than 5 or 6 cm is considered suggestive of adrenal cortical carcinoma, and many will show evidence of metastatic disease. In the absence of metastases, the differential diagnosis is usually that of carcinoma versus adenoma. The larger the mass, the greater is the likelihood of carcinoma, although on rare occasions adenomas can be larger than 5 cm and can have large regions of hemorrhage, necrosis, and calcifications. The size criterion for resection of adrenal incidentaloma varies widely, but most adrenal masses greater than 6 cm are resected for fear of possible adrenal carcinoma.
Little is known about chemical-shift MR imaging and CT densitometry of adrenal cortical carcinoma. In the reported series of attenuation values and enhancement washout curves on delayed enhanced CT, only one included three cases of adrenal carcinomas, but the carcinomas were included in the data set for nonadenomas and the locations of the individual cases in the scatterplots were not provided [62]. Adrenal carcinomas greater than 6 cm often have large regions of central necrosis or hemorrhage that invalidate attempts to assess contrast enhancement washout. Whether chemical-shift MR imaging, unenhanced CT, or delayed enhanced CT can reliably differentiate adenoma from carcinoma has not yet been established. The answer may depend on the histologic grade of malignancy involved.
In summary, most adrenal incidentalomas are cortical adenomas. Some adrenal masses have pathognomonic CT features such as hemorrhage, myelolipoma, and cysts, but most incidentalomas have nonspecific morphologic features. In patients with a primary extraadrenal neoplasm and no other evidence of distant metastatic disease, noninvasive imaging can reduce the necessity for percutaneous adrenal mass biopsy in most patients. Most adrenal adenomas are lipid-rich and can be correctly diagnosed on chemical-shift MR imaging or unenhanced CT. Most lipid-poor adenomas can be accurately characterized on delayed enhanced CT. Percutaneous biopsy can be limited to those masses whose imaging studies do not indicate an adenoma.
|
TopIntroductionSpecific Imaging FeaturesNonspecific Imaging FeaturesAdenoma Versus MetastasisAdenoma Versus CarcinomaReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  A. Karagiannis, D. P Mikhailidis, V. G Athyros, and F. Harsoulis Pheochromocytoma: an update on genetics and management Endocr. Relat. Cancer, December 1, 2007; 14(4): 935 - 956. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. H. Song, F. S. Chaudhry, and W. W. Mayo-Smith The Incidental Indeterminate Adrenal Mass on CT (> 10 H) in Patients Without Cancer: Is Further Imaging Necessary? Follow-Up of 321 Consecutive Indeterminate Adrenal Masses Am. J. Roentgenol., November 1, 2007; 189(5): 1119 - 1123. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S Bhatt, S Vanderlinde, R Farag, and V S Dogra Pararectal paraganglioma Br. J. Radiol., October 1, 2007; 80(958): e253 - e256. |
