Incidentaloma

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]

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.

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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.^[2] Hormonal evaluation includes^[3]:

• 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 (due to fat content) and rapid washout of contrast medium (50% or more of the contrast medium washes out at 10 minutes). 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^[3]

Renal incidentaloma

Most renal cell cancers are now found incidentally.^[4] Tumors less than 3 cm in diameter less frequently have aggressive histology.^[5]

Pituitary incidentaloma

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.^[6] When encountering such a lesion, long term surveillance has been recommended.^[7] 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). teststerone in men and estradial in amenorrheic women.

Thyroid incidentaloma

Incidental thyroid masses may be found in 9% of patients undergoing bilateral carotid duplex ultrasonography. ^[8]

Some experts^[9] 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.^[10] Ultrasonographic markers of malignancy are^[11]:

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

Parathyroid incidentaloma

Incidental parathyroid masses may be found in 0.1% of patients undergoing bilateral carotid duplex ultrasonography. ^[8]

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.^[12]

Others

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."^[13] The underlying pathology shows no unifying histological concept.

References

1. ^ ^{a b} 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.
2. ^ Grumbach MM, Biller BM, Braunstein GD, et al (2003). "Management of the clinically inapparent adrenal mass ("incidentaloma")". Ann. Intern. Med. 138 (5): 424-9. PMID 12614096.
3. ^ ^{a b} Young WF (2007). "Clinical practice. The incidentally discovered adrenal mass". N. Engl. J. Med. 356 (6): 601-10. doi:10.1056/NEJMcp065470. PMID 17287480.
4. ^ Reddan DN, Raj GV, Polascik TJ (2001). "Management of small renal tumors: an overview". Am. J. Med. 110 (7): 558-62. doi:10.1016/S0002-9343(01)00650-7. PMID 11343669.
5. ^ Remzi M, Ozsoy M, Klingler HC, et al (2006). "Are small renal tumors harmless? Analysis of histopathological features according to tumors 4 cm or less in diameter". J. Urol. 176 (3): 896-9. doi:10.1016/j.juro.2006.04.047. PMID 16890647.
6. ^ Hall WA, Luciano MG, Doppman JL, Patronas NJ, Oldfield EH (1994). "Pituitary magnetic resonance imaging in normal human volunteers: occult adenomas in the general population". Ann. Intern. Med. 120 (10): 817-20. PMID 8154641.
7. ^ Molitch ME (1997). "Pituitary incidentalomas". Endocrinol. Metab. Clin. North Am. 26 (4): 725-40. PMID 9429857.
8. ^ ^{a b} Steele SR, Martin MJ, Mullenix PS, Azarow KS, Andersen CA (2005). "The significance of incidental thyroid abnormalities identified during carotid duplex ultrasonography". Archives of surgery (Chicago, Ill. : 1960) 140 (10): 981-5. doi:10.1001/archsurg.140.10.981. PMID 16230549.
9. ^ Castro MR, Gharib H (2005). "Continuing controversies in the management of thyroid nodules". Ann. Intern. Med. 142 (11): 926-31. PMID 15941700.
10. ^ Shetty SK, Maher MM, Hahn PF, Halpern EF, Aquino SL (2006). "Significance of incidental thyroid lesions detected on CT: correlation among CT, sonography, and pathology". AJR. American journal of roentgenology 187 (5): 1349-56. doi:10.2214/AJR.05.0468. PMID 17056928.
11. ^ Papini E, Guglielmi R, Bianchini A, et al (2002). "Risk of malignancy in nonpalpable thyroid nodules: predictive value of ultrasound and color-Doppler features". J. Clin. Endocrinol. Metab. 87 (5): 1941-6. PMID 11994321.
12. ^ Gould MK, Fletcher J, Iannettoni MD, et al (2007). "Evaluation of Patients With Pulmonary Nodules: When Is It Lung Cancer?: ACCP Evidence-Based Clinical Practice Guidelines (2nd Edition)" 132 (3_suppl): 108S–130S. doi:10.1378/chest.07-1353. PMID 17873164.
13. ^ Mirilas P, Skandalakis JE (2002). "Benign anatomical mistakes: incidentaloma". The American surgeon 68 (11): 1026-8. PMID 12455801.