Adrenal Incidental Mass           See   adrenal_incidentalomas.pdf     adrenal_incidentalomas2007.pdf              REF:  ACP Medicine 2006

  Evaluation  |  Diff-Dx  |  Management
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 Incidentaloma:

Two Important Questions in evaluating an adrenal incidentaloma:

  1. Is it malignant?  If so, is it primary or metastataic cancer?
  2. Is it functional, secreting hormones?

Is it malignant?  If so, is it primary or metastataic cancer?

  • 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 time.
  • 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 nonadenomas.
    An absolute enhancement washout percentage of <60% at 15 min after giving contrast strongly suggests a nonadenoma.
  • 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 contrast.
  • 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 contrast.
  • 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 hormones?
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.)
  • Primary aldosteronism (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 functions:

  • 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


Differential Diagnosis:
  1. Benign adrenal hyperplasia or adenomas -  ACTH-independent Cushing syndrome, Primary hyperaldosteronism, Pheochromocytoma
  2. Malignant adrenal carcinoma - Adrenocortical cancer is a rare disease, with an annual incidence of 1 in 600,000.
  3. Metastatic adrenal cancer

Causes and Prevalence of adrenal incidentalomas  
(REF:  and  Endocr Rev 1995;16:460)

  • Adrenal cortical tumors           Prevalence (%)
    • Adenoma                          -  36 - 94%        
    • Nodular hyperplasia            -  7 - 17%
    • Adrenocortical carcinoma    -  1.2 - 11%
  • Adrenal medullary tumors
    • Pheochromocytoma            -  1.5 - 11%
  • Other Adrenal tumors
    • Myelolipoma                      -  7 - 15%
    • Lipoma                              -  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 alpha blockade


Management 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                                 REF:   adrenal_incidentalomas    

  • 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.