|About 300,000 abdominal CT and MRI procedures
are done annually in the United States for indications unrelated to the adrenals.
An incidental adrenal mass (incidentaloma) is found in about 4% of these
procedures, or 12,000 newly discovered masses each year. Assuming that
this is the incidence in the general population, there would be roughly
12 million such masses in the United States population.
Assuming that adrenal cancers are detectable by MRI 6 years before they become
clinically evident, the prevalence of adrenal cancer would be about 1
in 3,000 population. Therefore, 1 in 4,000 incidentally discovered
adrenal masses will be an adrenal cancer.
EVALUATION of Adrenal
Two Important Questions in evaluating an adrenal
Is it malignant? If so, is it primary or metastataic cancer?
Is it functional, secreting hormones?
Is it malignant? If so, is it primary or
The larger the adrenal mass, the more
likely it is malignant, the recommendations range for removal is from 4 to
6 cm, especially
over 6 cm or growing in size over
The noncontrast CT attenuation
coefficient feature ( in Hounsfield HU unit) is increasingly
used to differentiate benign adrenal adenomas and hyperplasias from malignant
lesions and pheochromocytomas.
Adrenal masses with higher HU values are more likely to be non-adenomas;
A consensus panel of the NIH recommended 10 HU, a threshold value that is
found to be 100% specific for ruling out nonadenomas.
Enhancement washout is valuable in
differentiating lipid-poor adrenal adenomas
(noncontrast HU>10) from
An absolute enhancement washout percentage of
<60% at 15 min after giving contrast strongly suggests a
CT characteristics that suggest
benign lesions are: smooth border, be round or oval in shape, have sharp
margins, conform to the shape of the adrenal gland, contain no calcification
within or on the edge of the tumor, be homogeneous, and not enhance after
MRI Scan is as effective as CT in
differentiating benign from malignant adrenal masses, but no clear advantage
over CT except in pregnant women, children, and patients with allergies to
Adrenal Scintigraphy (iodomethyl-norcholesterol
I 131) may also help differentiate benign from malignant adrenal
masses larger than 2 cm. This test is not widely available and takes
5-7 days to complete, limiting its usefulness.
Positron Emission Tomography (PET) is
nearly 100% sensitive and 94-95% specific in differentiate malignant from
benign adrenal lesions in patients with proven or suspected malignancy. It
is expensive and not widely available, and is not recommended for routine
evaluation of adrenal incidentalomas.
Fine-needle aspiration biopsy of the adrenal
mass in patient with noncontrast CT attenuation coefficient value
of > 10 HU. It cannot, however, always differentiate an adrenaocortical
carcinoma from an adrenal adenoma. To avoid causing a possible hypertensive
crisis, pheochromoctoma should always be excluded before this test.
A mass that displays slow washout can be assumed to be a metastasis.
If the patient has a known malignancy, the adrenal mass can be treated as
part of the primary process. If there is no known primary malignancy, the
mass could be the first manifestation of metastasis or a rare nascent
adrenocortical carcinoma. Percutaneous needle biopsy can readily differentiate
between these two possibilities, but it does involve risks, such as pneumothorax
and tumor seeding. Alternatively, the mass can be removed laparoscopically
and a pathologic analysis done.
Is it functional, secreting
6-20% of the adrenal incidentalomas have hormonal abnormalities, especially
if the adrenal masses are at least 3 cm.
The patients should be evaluated for
Pheochromocytoma (24h urine
metanephrines or plasma free metanephrines test)
Cushing syndrome (1 mg overnight
11 PM dexamethasone suppression test with next 8 AM plasma cortisol;
a normal result is < 5 ug/dL of cortisol; if the test is normal, it rule
out Cushing's syndrome, but if it is abnormal, further tests as 24h urine
free cortisol or 2mg q6h x 2 days dexamethason suppressin test for
Cushing syndrome is needed to confirm the diagnosis.)
(only if hypertensive, and especially with hypokalemia)
The best screening test is the AM ratio of the ambulatory plasma aldosterone
to the plasma renin activity; a ratio of 20 or greater along with a plasma
aldosterone > 10 ng/dL needs to be further evaluated by 24 h urine aldosterone
during salt loading.
Tests to be ordered to check for the adrenal mass
lytes, glucose, 24h urine metanephrines or plasma free metanephrines
1 mg overnight dexamethasone suppressin test with next 8AM plasma cortisol
If indicated, plasma aldosterone to plasma renin acitivity ratio
Benign adrenal hyperplasia or adenomas - ACTH-independent
Malignant adrenal carcinoma - Adrenocortical cancer is a rare disease, with
an annual incidence of 1 in 600,000.
Metastatic adrenal cancer
Causes and Prevalence of adrenal incidentalomas
and Endocr Rev 1995;16:460)
Adrenal cortical tumors
- 36 - 94%
Nodular hyperplasia - 7 -
Adrenocortical carcinoma - 1.2 - 11%
Adrenal medullary tumors
Pheochromocytoma - 1.5 - 11%
Other Adrenal tumors
- 7 - 15%
- 0 - 11%
Metastases to Adrenal Gland - 0 - 21%
Cyst and pseudocysts -
4 - 22 %
Hematoma and hemorrhage - 0 - 4 %
Infections, Granulomas - rare
In most series, 5% to 6% of incidental adrenal masses are
pheochromocytomas. This possibility should be excluded before biopsy
or operation so as to avoid the hypertensive crises that can be associated
with surgery. The safest course is to assume that the lesion is a
pheochromocytoma and to prepare all such patients for surgery with adequate
Approach to Adrenal Incidentalomas
The central question in the management of the incidental adrenal mass is
whether surgical removal is indicated.
Certainly, the tumor should be removed if it is metabolically functional,
as manifested by Cushing syndrome, the syndrome of mineralocorticoid
excess, or virilization or feminization for which there is no
other explanation. If there is no evidence of functionality, the tumor should
be studied with a CT contrast washout study. Benign adrenal adenomas are
lipid rich, whereas malignant ones tend to contain much more cellular
and intercellular water. Thus, water-soluble contrast agents tend to
wash out of benign lesions much faster than they do from malignant ones.
The accuracy of this procedure in experienced hands is very high, with greater
than 90% specificity and sensitivity.
Cleveland Clinic Approach 6-2006
If the noncontrast CT attenuation value is <
10 HU, and the mas is nonfunctional, we do not routinely obtain
any follow up imaging study. However, annual evaluation of hormonal
hypersecretin is recommended, esp if the mass is > 3 cm.
If the noncontrast CT attenuation value is >10
HU, and the mass is > 6 cm, we would refer the patient for
surgery. For smaller nonfunctional masses, we obtain the enhancement
washout percentage at 15 minutes: if less than 60%, we also refer the
patient for surgery. If the enhancement washout is >60%, patients
should have a follow up imaging study in 6-12 months and have the mass resected
if it grows by more than 1 cm.
If the mass is either functional or
malignant, patients are usually referred for surgery. But
medical therapy may be acceptable for primary aldosteronism that is secondary
to adrenocortical adenoma or hyperplasia.