Incidental imaging finding

Incidental adrenal masses on imaging are common (0.6 to 1.3% of all abdominal CT). Differential diagnosis include adenoma, myelolipoma, cyst, lipoma, pheochromocytoma, adrenal cancer, metastatic cancer, hyperplasia, and tuberculosis.{{cite journal |author=Cook DM |title=Adrenal mass |journal=Endocrinol. Metab. Clin. North Am. |volume=26 |issue=4 |pages=829–52 | date=December 1997 |pmid=9429862 |doi= 10.1016/s0889-8529(05)70284-x}} Some of these lesions are easily identified by radiographic appearance; however, it is often adenoma vs. cancer/metastasis that is most difficult to distinguish. Thus, clinical guidelines have been developed to aid in diagnosis and decision-making.{{Cite web|url=https://www.aace.com/files/adrenal-guidelines.pdf|title=2009 AACE/AAES Guidelines, Adrenal incidentaloma|access-date=17 September 2014|archive-date=29 August 2017|archive-url=https://web.archive.org/web/20170829230949/https://www.aace.com/files/adrenal-guidelines.pdf|url-status=dead}} Although adrenal incidentalomas are common, they are not commonly cancerous - less than 1% of all adrenal incidentalomas are malignant.

The first considerations are size and radiographic appearance of the mass. Suspicious adrenal masses or those ≥4 cm are recommended for complete removal by adrenalectomy. Masses <4 cm may also be recommended for removal if they are found to be hormonally active, but are otherwise recommended for observation.{{cite journal |vauthors=Grumbach MM, Biller BM, Braunstein GD, etal |title=Management of the clinically inapparent adrenal mass ("incidentaloma") |journal=Ann. Intern. Med. |volume=138 |issue=5 |pages=424–9 |year=2003 |pmid=12614096 |doi=10.7326/0003-4819-138-5-200303040-00013|s2cid=23454526 }} All adrenal masses should receive hormonal evaluation. Hormonal evaluation includes:{{cite journal |author=Young WF |title=Clinical practice. The incidentally discovered adrenal mass |journal=N. Engl. J. Med. |volume=356 |issue=6 |pages=601–10 |year=2007 |pmid=17287480 |doi=10.1056/NEJMcp065470}}

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

On CT scan, benign adenomas typically are of low radiodensity (due to fat content). A radiodensity equal to or below 10 Hounsfield units (HU) is considered diagnostic of an adenoma.{{cite web|url=http://www.radiologyassistant.nl/en/p421aee7c659fc/adrenals.html|archive-url=https://web.archive.org/web/20130307065115/http://www.radiologyassistant.nl/en/p421aee7c659fc/adrenals.html|url-status=dead|archive-date=7 March 2013|title=Adrenals - Differentiating benign from malignant|author=Theo Falke and Robin Smithuis|website=Radiology Assistant|access-date=2018-01-02}} An adenoma also shows rapid radiocontrast washout (50% or more of the contrast medium washes out at 10 minutes). If the hormonal evaluation is negative and imaging suggests benign lesion, follow up may be considered. Imaging at 6, 12, and 24 months and repeat hormonal evaluation yearly for 4 years is often recommended, but there exists controversy about harm/benefit of such screening as there is a high subsequent false-positive rate (about 50:1) and overall low incidence of adrenal carcinoma.{{cite journal |vauthors=Cawood TJ, Hunt PJ, O'Shea D, Cole D, Soule S |title=Recommended evaluation of adrenal incidentalomas is costly, has high false-positive rates and confers a risk of fatal cancer that is similar to the risk of the adrenal lesion becoming malignant; time for a rethink? |journal=Eur. J. Endocrinol. |volume=161 |issue=4 |pages=513–27 | date=October 2009 |pmid=19439510 |doi=10.1530/EJE-09-0234 |doi-access=free }}

Autopsy series have suggested that pituitary incidentalomas may be quite common. It has been estimated that perhaps 10% of the adult population may harbor such endocrinologically inert lesions.{{cite journal|year=1994|title=Pituitary magnetic resonance imaging in normal human volunteers: occult adenomas in the general population|journal=Ann. Intern. Med.|volume=120|issue=10|pages=817–20|doi=10.7326/0003-4819-120-10-199405150-00001|pmid=8154641|vauthors=Hall WA, Luciano MG, Doppman JL, Patronas NJ, Oldfield EH|s2cid=23833253}} Most of these lesions, especially those which are small, will not grow. However, some form of long-term surveillance has been recommended based on the size and presentation of the lesion.{{cite journal|author=Molitch ME|year=1997|title=Pituitary incidentalomas|journal=Endocrinol. Metab. Clin. North Am.|volume=26|issue=4|pages=725–40|doi=10.1016/S0889-8529(05)70279-6|pmid=9429857}} With pituitary adenomas larger than 1 cm, a baseline pituitary hormonal function test should be done, including measurements of serum levels of TSH, prolactin, IGF-1 (as a test of growth hormone activity), adrenal function (i.e. 24 hour urine cortisol, dexamethasone suppression test), testosterone in men, and estradiol in amenorrheic women.{{cite journal|author=Snyder|year=2021|title=Causes, presentation, and evaluation of sellar masses|url=https://www.uptodate.com/contents/causes-presentation-and-evaluation-of-sellar-masses|url-access=subscription}}

Incidental thyroid masses may be found in 9% of patients undergoing bilateral carotid duplex ultrasonography.{{cite journal|year=2005|title=The significance of incidental thyroid abnormalities identified during carotid duplex ultrasonography|journal=Archives of Surgery|volume=140|issue=10|pages=981–5|doi=10.1001/archsurg.140.10.981|pmid=16230549|vauthors=Steele SR, Martin MJ, Mullenix PS, Azarow KS, Andersen CA|doi-access=}}

Some experts{{cite journal|year=2005|title=Continuing controversies in the management of thyroid nodules|journal=Ann. Intern. Med.|volume=142|issue=11|pages=926–31|doi=10.7326/0003-4819-142-11-200506070-00011|pmid=15941700|vauthors=Castro MR, Gharib H|s2cid=41308483}} recommend that nodules > 1 cm (unless the TSH is suppressed) or those with ultrasonographic features of malignancy should be biopsied by fine needle aspiration. Computed tomography is inferior to ultrasound for evaluating thyroid nodules.{{cite journal|year=2006|title=Significance of incidental thyroid lesions detected on CT: correlation among CT, sonography, and pathology|journal=AJR. American Journal of Roentgenology|volume=187|issue=5|pages=1349–56|doi=10.2214/AJR.05.0468|pmid=17056928|vauthors=Shetty SK, Maher MM, Hahn PF, Halpern EF, Aquino SL}} Ultrasonographic markers of malignancy are:{{cite journal|year=2002|title=Risk of malignancy in nonpalpable thyroid nodules: predictive value of ultrasound and color-Doppler features|journal=J. Clin. Endocrinol. Metab.|volume=87|issue=5|pages=1941–6|doi=10.1210/jcem.87.5.8504|pmid=11994321|vauthors=Papini E, Guglielmi R, Bianchini A, etal|doi-access=free}}

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

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

The American College of Radiology recommends the following workup for thyroid nodules as incidental imaging findings on CT, MRI or PET-CT:{{cite web|url=https://radiopaedia.org/blog/reporting-of-incidental-thyroid-nodules-on-ct-and-mri-1|title=Reporting of incidental thyroid nodules on CT and MRI|author=Jenny Hoang|date=2013-11-05|website=Radiopaedia}}, citing:

• {{cite journal|last1=Hoang|first1=Jenny K.|last2=Langer|first2=Jill E.|last3=Middleton|first3=William D.|last4=Wu|first4=Carol C.|last5=Hammers|first5=Lynwood W.|last6=Cronan|first6=John J.|last7=Tessler|first7=Franklin N.|last8=Grant|first8=Edward G.|last9=Berland|first9=Lincoln L.|title=Managing Incidental Thyroid Nodules Detected on Imaging: White Paper of the ACR Incidental Thyroid Findings Committee|journal=Journal of the American College of Radiology|volume=12|issue=2|year=2015|pages=143–150|issn=1546-1440|doi=10.1016/j.jacr.2014.09.038|pmid=25456025}}

Studies of whole body screening computed tomography find abnormalities in the lungs of 14% of patients.{{cite journal|year=2005|title=Whole-body CT screening: spectrum of findings and recommendations in 1192 patients|journal=Radiology|volume=237|issue=2|pages=385–94|doi=10.1148/radiol.2372041741|pmid=16170016|vauthors=Furtado CD, Aguirre DA, Sirlin CB, etal}} Clinical practice guidelines by the American College of Chest Physicians advise on the evaluation of the solitary pulmonary nodule.{{cite journal|year=2007|title=Evaluation of Patients With Pulmonary Nodules: When Is It Lung Cancer?: ACCP Evidence-Based Clinical Practice Guidelines (2nd Edition)|journal=Chest|volume=132|issue=3_suppl|pages=108S–130S|doi=10.1378/chest.07-1353|pmid=17873164|vauthors=Gould MK, Fletcher J, Iannettoni MD, etal}}

File:Contrast-enhanced ultrasonography of benign lesion.jpg is confirmed cystic and benign with contrast-enhanced renal ultrasonography.]]

Most renal cell carcinomas are now found incidentally.{{cite journal |vauthors=Reddan DN, Raj GV, Polascik TJ |title=Management of small renal tumors: an overview |journal=Am. J. Med. |volume=110 |issue=7 |pages=558–62 |year=2001 |pmid=11343669 |doi=10.1016/S0002-9343(01)00650-7 }} Tumors less than 3 cm in diameter less frequently have aggressive histology.{{cite journal |vauthors=Remzi M, Ozsoy M, Klingler HC, etal |title=Are small renal tumors harmless? Analysis of histopathological features according to tumors 4 cm or less in diameter |journal=J. Urol. |volume=176 |issue=3 |pages=896–9 |year=2006 |pmid=16890647 |doi=10.1016/j.juro.2006.04.047}}

A CT scan is the first choice modality for workup of solid masses in the kidneys. Nevertheless, hemorrhagic cysts can resemble renal cell carcinomas on CT, but they are easily distinguished with Doppler ultrasonography (Doppler US). In renal cell carcinomas, Doppler US often shows vessels with high velocities caused by neovascularization and arteriovenous shunting. Some renal cell carcinomas are hypovascular and not distinguishable with Doppler US. Therefore, renal tumors without a Doppler signal, which are not obvious simple cysts on US and CT, should be further investigated with contrast-enhanced ultrasound, as this is more sensitive than both Doppler US and CT for the detection of hypovascular tumors.Content initially copied from: {{cite journal|last1=Hansen|first1=Kristoffer|last2=Nielsen|first2=Michael|last3=Ewertsen|first3=Caroline|title=Ultrasonography of the Kidney: A Pictorial Review|journal=Diagnostics|volume=6|issue=1|year=2015|pages=2|issn=2075-4418|doi=10.3390/diagnostics6010002|pmid=26838799|pmc=4808817|doi-access=free}} [https://creativecommons.org/licenses/by/4.0/ (CC-BY 4.0)]

The increasing use of MRI, often during diagnostic work-up for back or lower extremity pain, has led to a significant increase in the number of incidental findings that are most often clinically inconsequential. The most common include:{{cite journal |vauthors=Park HJ, Jeon YH, Rho MH, etal |title=Incidental findings of the lumbar spine at MRI during herniated intervertebral disk disease evaluation |journal=AJR Am J Roentgenol |volume=196 |issue=5 |pages=1151–5 | date=May 2011 |pmid=21512084 |doi=10.2214/AJR.10.5457 }}

• vertebral hemangioma
• fibrolipoma (a lipoma with fibrous areas)
• Tarlov cyst

Sometimes normally asymptomatic findings can present with symptoms and these cases when identified cannot then be considered as incidentalomas.{{citation needed|date=August 2020}}

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."{{cite journal |vauthors=Mirilas P, Skandalakis JE |title=Benign anatomical mistakes: incidentaloma |journal=The American Surgeon |volume=68 |issue=11 |pages=1026–8 |year=2002 |doi=10.1177/000313480206801119 |pmid=12455801 }} The underlying pathology shows no unifying histological concept.{{citation needed|date=May 2022}}

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