This document provides an overview of adrenal incidentalomas. It defines incidentalomas as unsuspected adrenal masses greater than 1 cm found on imaging for unrelated reasons. Nearly 20% may require surgery. Evaluation involves imaging to characterize the mass and metabolic testing to check for hormone hypersecretion. Computed tomography and MRI are used to identify lipid-rich adenomas. Biopsy has limited utility due to risk and inability to differentiate adenoma from carcinoma. Masses larger than 4 cm or those that grow over 1 cm may require resection. Metabolic testing evaluates for cortisol, catecholamine, aldosterone, and sex steroid hypersecretion, though sex hormone testing is not routinely recommended.

1. OVERVIEW OF THE
ADRENAL
INCIDENTALOMA

2. Incidentaloma
Definition
 Adrenal incidentalomas are unsuspected
adrenal masses greater than 1 cm in
diameter identified on cross-sectional
imaging performed for seemingly unrelated
causes
 Frequency of adrenal incidentalomas is
relatively high, with reporting an incidence
of approximately 5%

3.  Incidence of the incidental adrenal mass
increases with age,with a risk of less than
0.5% in individuals in their 20s and up to
7% in those 70 years of age or older
 Nearly 20% of adrenal incidentalomas are
found to be potential surgical lesions
 The two characteristics of primary clinical
relevance are imaging and metabolic activity
or functional status

5. Imaging of Adrenal Masses
 Ultrasonography is a suboptimal imaging
modality for detecting and fully
characterizing adrenal lesions
 Ultrasonography is responsible for identifying
individuals with adenomas, right-sided lesions
appear to be more common.

6. Computed Tomography and
Magnetic Resonance Imaging.
 CT and MRI permit cross-sectional and
reconstructed anatomic image
characterization of the adrenals and serve
as the cornerstone for adrenal evaluation.
 Most adrenal incidentalomas are small
homogeneous masses with regular
contours that cannot be immediately given
a pathologic label.

7.  An unenhanced CT scan is the first, and
perhaps single best, and most easily
interpreted test for intracellular lipid and
therefore can diagnose an adrenal
adenoma in more than 70% of cases.
 Low attenuation (<10 HU) on unenhanced
CT corresponds to high intracytoplasmic
lipid content and is diagnostic for an
adrenal adenoma

8.  Despite the high specificity of the 10-HU cutoff,
few low-density (<10 HU) pheochromocytomas
have been reported, underscoring the
importance of a metabolic workup for all
adrenal lesions
 CECT -Irregular margins and an enhancing rim
can be quite specific for malignancy

9. Computed Tomography Washout
Study
 Approximately 30% of adrenal adenomas
exhibit an attenuation of greater than 10 HU
on unenhanced CT owing to their lower
lipid content.
 These “atypical adenomas” are
indistinguishable from nonadenomas on
noncontrast CT density measurements
alone
 Fortunately, lipid-poor adenomas possess
identical properties to lipid-rich adenomas
regarding their rapid loss (washout) of
enhancement after CT contrast load

10.  An absolute percent washout (comparing
noncontrast values with 15-minute
postcontrast density values) of greater than
60%, or a relative percent washout (RPW)
(comparing arterial phase density
measurements with 15-minute postcontrast
density values) of greater than 40% on
delayed (washout) imaging, is indicative of
adenoma

11. MRI
 MRI harnesses the interference between
signal collected from fat and water tissue
to evaluate for intracellular lipid content
 On such opposed phase chemical shift
imaging, signal intensity loss on out-of-
phase sequences, when compared with in-
phase imaging, signifies the presence of
intracellular lipid and definitively identifies
the lesions in question is an adenoma

13.  Nevertheless, CT washout studies are
considered the gold standard and appear
to surpass opposed phase chemical shift
MRI in their sensitivity for identifying
adenomas
 MIBG imaging has a limited role in the routine
evaluation of adrenal incidentalomas.
 FDG PET is best reserved for cases in which
CT imaging and clinical data are inconclusive

14. Biopsy of Adrenal Masses
 The role of adrenal biopsy has been limited
for the followingreasons:
 (1) modern imaging in the context of
clinical characteristics affords superb
diagnostic capabilities,
 (2) histologically,adenomas cannot be
reliably differentiated from adrenal
carcinomas,
 (3) adrenal biopsy is not without risk

15.  Adrenal biopsy should be pursued only
when limitations of imaging have been
reached and when the physician and
patient are certain that the result of biopsy
will influence management.
 When used to differentiate benign from
metastatic disease, adrenal biopsy carries
favorable test characteristics.

16. Size and Growth
 A relationship does exist between the size
of an adrenal lesion and its malignant
potential, with larger masses more likely to
exhibit adverse clinical and pathologic
features
 Masses that exceed 6 cm should be
considered malignant until proven benign,
which usually requires definitive resection.

17.  Although management of masses between 4
cm and 6 cm is controversial, thought leaders
in the field advise that in otherwise healthy
individuals, masses 4 cm or larger should be
resected.
 Kinetics of growth should be followed. The
current recommendation is to resect masses
that grow over 1 cm;

18. Assessment of Function of
Adrenal Masses
 The NIH consensus statement
recommends metabolic testing for all
adrenal incidentalomas
 Current practice is to test all new adrenal
masses for cortisol and catecholamine
hypersecretion. In patients with a history of
hypertension, aldosterone hypersecretion
should also assessed

19. Testing for Cortisol
Hypersecretion
 Three first-line tests are available to screen
patients with incidentalomas for Cushing
syndrome:
 (1)LD-DST,
 (2) a late-night salivary cortisol test, and
 (3) a 24-hour UFC evaluation.

20. Testing for Aldosterone
Hypersecretion
 The screening test of choice for Conn
syndrome is the ratio of morning plasma
aldosterone (ng/dL) to renin (ng/mL/hr).
 An ARR of 20 (some suggest 30) along with
a concomitant aldosterone concentration
above 15 ng/mL is indicative of Conn
syndrome

21. Testing for Catecholamine
hypersecretion
 Free fractionated plasma metanephrines
and the 24-hour urinary fractionated
metanephrine test constitute the mainstay
for pheochromocytoma testing.
 Acetaminophen can produce a false-
positive result owing to cross reactivity in
the assay and should be stopped for at
least 5 days before testing

22. Testing for Adrenal Sex Steroid
Hypersecretion
 Hypersecretion of adrenal sex steroids by
adrenal masses, especially incidentalomas, is
exceedingly rare.
 The most common adrenal mass that
hypersecretes sex steroid is an adrenal
carcinoma that concomitantly exhibits cortisol
hypersecretion
 Routine testing of incidentalomas for sex
hormones is currently not recommended