Incidentaloma

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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]

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.[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 (<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.[4] 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] However, even patients without low attenuation

Brain incidentaloma

Almost 2% of MRI scans of adults aged 55 years or greater will detect neoplasms.[5] The most common are meningioma (0.9%), followed by pituitary adenoma (0.3%).[5]

Pituitary incidentaloma

10% of the adult population may harbor such endocrinologically pituitary adenomas.[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), 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. [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.[9]

Renal incidentaloma

Most renal cell cancers are now found incidentally.[10] Tumors less than 3 cm in diameter less frequently have aggressive histology.[11]

Thyroid incidentaloma

Incidental thyroid masses may be found in 9% of patients undergoing bilateral carotid duplex ultrasonography. [8] The physical examination is only accurate if the nodule is at least 1 cm.[12] The risk of malignancy in these nodules is 5-10%.[13]

Some experts[14][13][15][16] 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 recommendations suggests routine fine needle aspiration of nodules 1 to 1.4 cm in size is not desirable.[17]

Ultrasonograpy alone has insufficient sensitivity of 83% (specificity of 74%).[18]Computed tomography is inferior to ultrasound for evaluating thyroid nodules.[19] Ultrasonographic markers of thyroid cancer are[14]:

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

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

References

  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. ↑ 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. [e]
  3. ↑ 3.0 3.1 Young WF (2007). "Clinical practice. The incidentally discovered adrenal mass". N. Engl. J. Med. 356 (6): 601-10. DOI:10.1056/NEJMcp065470. PMID 17287480. Research Blogging.
  4. ↑ 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.
  5. ↑ 5.0 5.1 Vernooij MW, Ikram MA, Tanghe HL, et al (2007). "Incidental findings on brain MRI in the general population". N. Engl. J. Med. 357 (18): 1821–8. DOI:10.1056/NEJMoa070972. PMID 17978290. Research Blogging.
  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. [e]
  7. ↑ Molitch ME (1997). "Pituitary incidentalomas". Endocrinol. Metab. Clin. North Am. 26 (4): 725-40. PMID 9429857. [e]
  8. ↑ 8.0 8.1 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. Research Blogging.
  9. ↑ 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. Research Blogging.
  10. ↑ 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. Research Blogging.
  11. ↑ 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. Research Blogging.
  12. ↑ Tan GH, Gharib H, Reading CC (1995). "Solitary thyroid nodule. Comparison between palpation and ultrasonography". Arch. Intern. Med. 155 (22): 2418–23. PMID 7503600. [e]
  13. ↑ 13.0 13.1 Castro MR, Gharib H (2005). "Continuing controversies in the management of thyroid nodules". Ann. Intern. Med. 142 (11): 926-31. PMID 15941700. [e]
  14. ↑ 14.0 14.1 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. [e]
  15. ↑ Mandel SJ (December 2004). "A 64-year-old woman with a thyroid nodule". JAMA 292 (21): 2632–42. DOI:10.1001/jama.292.21.2632. PMID 15572721. Research Blogging.
    Diagnostic algorithm at http://jama.ama-assn.org/cgi/content/full/292/21/2632/JXR40007F1
  16. ↑ Hegedüs L (October 2004). "Clinical practice. The thyroid nodule". N. Engl. J. Med. 351 (17): 1764–71. DOI:10.1056/NEJMcp031436. PMID 15496625. Research Blogging.
    Diagnostic algorithm at http://content.nejm.org/cgi/content/full/351/17/1764/F1
  17. ↑ McCartney CR, Stukenborg GJ (August 2008). "Decision analysis of discordant thyroid nodule biopsy guideline criteria". J. Clin. Endocrinol. Metab. 93 (8): 3037–44. DOI:10.1210/jc.2008-0448. PMID 18505762. Research Blogging.
  18. ↑ Moon WJ, Jung SL, Lee JH, et al (June 2008). "Benign and malignant thyroid nodules: US differentiation--multicenter retrospective study". Radiology 247 (3): 762–70. DOI:10.1148/radiol.2473070944. PMID 18403624. Research Blogging. “42$ of patients had malignancy is this selected population”
  19. ↑ 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. Research Blogging.
  20. ↑ Mirilas P, Skandalakis JE (2002). "Benign anatomical mistakes: incidentaloma". The American surgeon 68 (11): 1026-8. PMID 12455801. [e]
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