Duke Internal Medicine Residency Curriculum
Approach to the
Incidental Adrenal Nodule
Author: Andrew Hope, MD
Editor: Amy Shaheen, MD, Assistant Professor
of Clinical Medicine
Duke University Medical Center
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Duke Internal Medicine Residency Curriculum
Adrenal Nodules: Definition & Incidence
• Definition:
– A lesion incidentally discovered radiographically
measuring >1cm.
• Incidence:
– At autopsy 9% of normotensive patients, and 12%
of hypertensive pts, will have a 2-4cm adrenal
mass.
– On CT scan, 0.4% of live patients will have >1cm
“incidentaloma”
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Adrenal Nodules: Differential Diagnosis
• Benign (70% of time
in non-known CA
pts)
–
–
–
–
Adenoma
Myelolipoma
Adrenal cysts
Hematoma
• Malignant
– Pheochromocytoma
– Metastases
– Adrenal cortical
carcinoma
– Ganglioneuroma
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Adrenal Nodules: Approach to excluding malignancy
1) Evaluate patient risk factors:
Patients with history of known
cancer will have malignancy 75%
of time. Otherwise, age, race,
most other patient characteristics
not known to be predictive of
malignancy.
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Adrenal Nodules: Radiographic characteristics of lesion
2) Examine Radiographic characteristics of lesion:
There are a host of CT and MR imaging characteristics
that help distinguish among benign adenomas,
adrenocortical CA, pheochromocytoma, cysts, and
hematomas. Some of them are listed here, although
clearly a radiologist’s assistance will be needed to
make the diagnosis (as long as we order the right
test—according to NIH guidelines, CT and MRI are
equivalent in evaluation of adrenal mass):
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Adrenal Nodules: Features of benign adenoma
• Features of benign adenoma:
• Round, homogeneous density; sharp
margination; size<4cm; low unenhanced
attenuation; limited enhancement with IV
contrast on CT; isointensity with liver both
T1 and T2 on MR; chemical shift c/w lipid on
MR
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Adrenal Nodules: Features of Adrenocortical CA
• Features of adrenocortical CA:
• Irregular shape; inhomogeneous density 2/2
tumor necrosis; tumor calcification;
diameter>4cm; unilateral; high unenhanced
CT attenuation; inhomogeneous
enhancement with CT contrast;
hypointensity c/w liver T1 MR, high/intermed
T2 MR; evidence of invasion/metastasis
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Adrenal Nodules: Features of pheochromocytoma
• Features of pheochromocytoma:
– Enhancement with CT contrast; high signal
on T2 MR; cystic/hemorrhagic changes;
variable size, bilateral
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Adrenal Nodules: Features of metastatic lesions
• Features of metastatic lesions:
– Irregular shape, inhomogeneous; often bilateral;
high unenhanced CT attenuation; enhancement
with contrast on CT; isointensity with liver T1 MR
and high/intermed intensity T2
• Note: Adrenal cysts, hemorrhage,
myelilopoma are distinguished with other
characteristics
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Adrenal Nodules: Hypersecreting lesions
3) Perform hormonal evaluation for
hypersecreting lesions.
(this should be done in all patients)
– Cortisol-secreting tumors (10% of cases, 5-8% are
subclinical Cushing’s).
• Clinical features: obesity, hypertension, glucose
intolerance, hypercholesterolemia
• All pts with adrenal mass should have 1mg dexamethasone
suppression test performed (NIH consensus guidelines)
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Adrenal Nodules: Pheochromacytoma, Aldosteronoma
• Pheochromocytoma (3-10% of adrenal masses). Plasma free
metanephrines should be sent in all pts with adrenal mass (NIH
consensus guidelines). This test is 99% sensitive and 90%
specific for pheo. Alternatively, a 24 hr urine could be collected
for metanephrines, vanillylmandelic acid (VMA), and free
catecholamines
• Aldosteronoma (rare, <1%). Patients with adrenal incidentaloma
and hypertension should be evaluated with plasma aldosterone
and renin, even if not hypokalemic (NIH guidelines).
• Summary: all patients need 1mg dexamethasone
suppression test and plasma free metanephrines. Add
plasma rennin/aldo if hypertension present.
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Adrenal Nodules: Further Studies
FNA. This is useful only to
distinguish metastatic lesions from
adrenal tumors. For example, a
case series found that 2/3 of lung
cancer patients with adrenal masses
had a benign adrenal lesion.
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Adrenal Nodules: Surgery vs. Conservative follow up
4) Decide surgery vs. conservative follow up.
• Criteria for surgery:
– Size
• Over 6 cm  surgery. Less than 4 cm  clinical follow up. 4-6
cm  consider in context of other features of patient and mass.
• Functional tumors.
– Clinically apparent cortisol-secreting tumors  surgery.
Subclinical cortisol-secreting tumors  “data insufficient” for
recommendation, i.e. refer to specialist
– Pheochromocytoma, dx supported by lab findings.  surgery
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Adrenal Nodules: Follow up for unresected adrenal masses
• Follow up for unresected adrenal masses:
– Imaging. A repeat imaging study (CT or MR) should
be performed 6-12 months after the initial study to
evaluate change in size. Adrenocortical CA is rapidly
growing, and this interval is sufficient to detect the
size change.
– Hormonal evaluation. Pts should have yearly 1mg
overnight dexamethasone suppression tests and
urine or plasma metanephrine measurement for 4
years. This practice rules out the development of a
hypersecreting tumor.
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Adrenal Nodules: Question (1)
A 42 y/o woman presents for evaluation
of a 2.8-cm left adrenal mass. She was
seen in the ER 1 week ago for
abdominal pain. CT scan shows only the
adrenal mass. Physical examination,
vital signs, and review of systems are all
normal. Medical history and family
history are unremarkable.
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Adrenal Nodules: Correct Answer rationale
C) The first step in management is an evaluation of serum and
urine hormone levels to determine whether the mass is functional
or nonfunctional. If it is nonfunctional, follow-up CT and repeat
hormone testing at 6-12 months are indicated to ensure the mass
is not enlarging or beginning to produce hormones. At 2.8 cm,
the mass has a low malignant or functional potential, and
therefore there is no immediate indication for removal of the
mass, biopsy, or further imaging. (MKSAP-13)
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Adrenal Nodules: Sources
• NIH Consensus Panel, “Management of the Clinically Inapparent
Adrenal Mass”, NIH Consensus and State-of-the-Science
Statements, 2002: Volume 19, no. 2
• UTDOL, 2005
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