Incidental findings are previously undiagnosed medical or psychiatric conditions that are discovered unintentionally and are unrelated to the current medical or psychiatric condition which is being treated or for which tests are being performed. Incidental findings may be uncovered in a variety of settings such as in test subjects during medical research, during the course of an autopsy, or during genetic testing.
The ethical issues around responding to incidental findings are complex.
An incidentaloma is a tumor found by coincidence which is often benign and does not cause any clinically significant symptoms; however a small percentage do turn out to be malignant. Incidentalomas are common, with up to 7% of all patients over 60 harboring 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.
Incidental findings in neuroimaging are common, with the prevalence of neoplastic incidental brain findings increasing with age.  Even in healthy subjects acting as controls in research incidental findings are not rare.
Pituitary adenomas are tumors that occur in the pituitary gland, and account for about 15% of intracranial neoplasms. They often remain undiagnosed, and are often an incidental finding during autopsy. Microadenomas (<10mm) have an estimated prevalence of 16.7% (14.4% in autopsy studies and 22.5% in radiologic studies).
- Wolf S.M., Paradise J., Caga-anan C. (2008). "The Law of Incidental Findings in Human Subjects Research". J Law, Med Ethics 36 (2): 361–383. doi:10.1111/j.1748-720X.2008.00281.x. PMC 2581517. PMID 18547206.
- Light TD, Royer NA, Zabell J et al. (2011). "Autopsy after traumatic death--a shifting paradigm". J Surg Res. 167 (1): 121–4. doi:10.1016/j.jss.2009.07.009. PMC 2891351. PMID 20031159.
- Clayton EW (2008). "Incidental findings in genetics research using archived DNA". J Law Med Ethics 36 (2): 286–91. doi:10.1111/j.1748-720X.2008.00271.x. PMC 2576744. PMID 18547196.
- Couzin-Frankel, Jennifer (2013). "President's Bioethics Panel Weighs in on How U.S. Should Handle Incidental Findings". news.sciencemag.org. Retrieved 13 December 2013.
- 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.
- Ladd SC, Warlow C, Wardlaw JM et al. (Aug 2009). "Incidental findings on brain magnetic resonance imaging: systematic review and meta-analysis". BMJ 339: b3016. doi:10.1136/bmj.b3016. PMC 2728201. PMID 19687093.
- Cramer SC, Wu J, Hanson JA et al. (Apr 2011). "A system for addressing incidental findings in neuroimaging research". Neuroimage 55 (3): 1020–3. doi:10.1016/j.neuroimage.2010.11.091. PMC 3057347. PMID 21224007.
- Ezzat S, Asa SL, Couldwell WT, Barr CE, Dodge WE, Vance ML, McCutcheon IE. (August 2004). "The prevalence of pituitary adenomas: a systematic review". Cancer 101 (3): 613–9. doi:10.1002/cncr.20412. PMID 15274075.
- Asa SL (August 2008). "Practical pituitary pathology: what does the pathologist need to know?". Arch. Pathol. Lab. Med. 132 (8): 1231–40. doi:10.1043/1543-2165(2008)132[1231:PPPWDT]2.0.CO;2. PMID 18684022. Retrieved 2008-09-03.[dead link]