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.

When faced with an unexpected finding on diagnostic imaging, the clinician is often faced with the dilemma whether to inform the patient of this finding, particularly if it is not completely certain if the finding is harmless.

Often, some other tests are required to determine the exact nature of an incidentaloma. In adrenal gland tumors, for example, a dexamethasone suppression test is often used to detect cortisol excess. Tumors under 3 cm are generally considered benign and are only treated if there are grounds for a diagnosis of Cushing's syndrome.

Other organs that can harbor incidentalomas are the pituitary gland and the liver (often a hemangioma).

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