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. Hormonal evaluation includes:- 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
Renal incidentaloma
Most renal cell cancers are now found incidentally. Tumors less than 3 cm in diameter less frequently have aggressive histology.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. When encountering such a lesion, long term surveillance has been recommended. 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.Some experts 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. Ultrasonographic markers of malignancy are:
- 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.Pulmonary nodule
Studies of whole body screening computed tomography find abnormalities in the lungs of 14% of patients. Clinical practice guidelines by the American College of Chest Physicians advise on the evaluation of the solitary pulmonary nodule.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." The underlying pathology shows no unifying histological concept.References
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Last updated on Thursday July 03, 2008 at 19:34:07 PDT (GMT -0700)
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