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In medicine, an incidentaloma is a tumor (-oma) found by coincidence (incidental) without clinical symptoms and suspicion. It is a common problem: up to 7% of all patients over 60 may harbor a benign growth, often of the adrenal gland, which is detected when diagnostic imaging is used for the analysis of unrelated symptoms. With the increase of "whole-body CT scanning" as part of health screening programs, the chance of finding incidentalomas is expected to increase. 37% of patients receiving whole-body CT scan may have abnormal findings that need further evaluation.[1] Radiologists may be more likely to detect incidental findings when a picture of the patient's face accompanies their computed tomography.[2]

When faced with an unexpected finding on diagnostic imaging, the clinician faces the challenge to prove that the lesion is indeed harmless. Often, some other tests are required to determine the exact nature of an incidentaloma.

Adrenal incidentaloma

In adrenal gland tumors, a dexamethasone suppression test is often used to detect cortisol excess, and metanephrines or catecholamines for excess of these hormones. Tumors under 3 cm are generally considered benign and are only treated if there are grounds for a diagnosis of Cushing's syndrome or pheochromocytoma.[3] Hormonal evaluation includes[4]:

  • 1-mg overnight dexamethasone suppression test
  • 24-hour urinary specimen for measurement of fractionated metanephrines and catecholamines
  • plasma aldosterone concentration and plasma renin activity if hypertension is present

On CT scan, benign adenomas typically are low radiographic density (<10 Hounsfield units) due to fat content and rapid washout of contrast medium (50% or more of the contrast medium washes out at 10 minutes). However, even if attenuation is great than 10 H masses are likely benign as long as they have no other worrisome features such as heterogeneity or irregularity.[5] If the hormonal evaluation is negative and imaging suggests benign, followup should be considered with imaging at 6, 12, and 24 months and repeat hormonal evaluation yearly for 4 years[4] However, even patients without low attenuation

Brain incidentaloma

Almost 2% of MRI scans of adults aged 55 years or greater will detect neoplasms.[6] The most common are meningioma (0.9%), followed by pituitary adenoma (0.3%).[6]

Pituitary incidentaloma

10% of the adult population may harbor such endocrinologically pituitary adenomas.[7] When encountering such a lesion, long term surveillance has been recommended.[8] Also baseline pituitary hormonal function needs to be checked, including measurements of serum levels of TSH, prolactin, IGF-I (as a test of growth hormone activity), adrenal function (i.e. 24 hours urine corticol,dexamethasone suppression test), and teststerone in men and estradial in amenorrheic women.

Parathyroid incidentaloma

Incidental parathyroid masses may be found in 0.1% of patients undergoing bilateral carotid duplex ultrasonography. [9]

Pulmonary nodule

Studies of whole body screening computed tomography find abnormalities in the lungs of 14% of patients.[1] Clinical practice guidelines by the American College of Chest Physicians advise on the evaluation of the solitary pulmonary nodule.[10]

Renal incidentaloma

Most renal cell cancers are now found incidentally.[11] Tumors less than 3 cm in diameter less frequently have aggressive histology[12], grow slowly if at all[13][14].

Thyroid incidentaloma

Incidental thyroid nodules may be found in 9% of patients undergoing bilateral carotid duplex ultrasonography. [9] The physical examination is only accurate if the nodule is at least 1 cm.[15] The risk of malignancy in these nodules is 5-10%.[16]

Some experts[17][18][19][20] recommend that nodules > 8 to 10 mm (unless the TSH is suppressed) or those with ultrasonographic features of thyroid cancer should be biopsied by fine needle aspiration. A decision analysis of conflicting clinical practice guidelines suggests routine fine needle aspiration of nodules 1 to 1.4 cm in size is not desirable.[21]

Ultrasonography alone has insufficient sensitivity of 83% (specificity of 74%)[22] to 87%[17]. Computed tomography is inferior to ultrasound for evaluating thyroid nodules.[23] Ultrasonographic markers of thyroid cancer are:[17]

  • solid hypoechoic appearance
  • irregular or blurred margins
  • intranodular vascular pattern
  • microcalcifications
  • Irregular margins
  • intranodular vascular spots
  • microcalcifications


Other organs that can harbor incidentalomas include the liver (often a hemangioma).

Scientific criticism

The concept of the incidentaloma has been criticized, as such lesions do not have much in common other than the history of an incidental identification and the assumption that they are clinically inert. It has been proposed just to say that such lesions have been "incidentally found."[24] The underlying pathology shows no unifying histological concept.


  1. 1.0 1.1 Furtado CD, Aguirre DA, Sirlin CB, et al (2005). "Whole-body CT screening: spectrum of findings and recommendations in 1192 patients". Radiology 237 (2): 385-94. DOI:10.1148/radiol.2372041741. PMID 16170016. Research Blogging.
  2. Helliker K. Say Cheese: Do Photos Help Doctors See Patients Better?. The Wall Street Journal Dec 2, 2008. (this is a preliminary report of research by Yehonatan N. Turner that was presented at the Radiological Society of North America conference.
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  5. Song JH, Chaudhry FS, Mayo-Smith WW (2007). "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". AJR Am J Roentgenol 189 (5): 1119–23. DOI:10.2214/AJR.07.2167. PMID 17954649. Research Blogging.
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    Diagnostic algorithm at
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    Diagnostic algorithm at
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