Advanced imaging tests for many common health problems may catch something else entirely: incidentalomas that can create anxiety about tumors but more often than not, don't turn out to be cancer, a research review suggests.

Incidentalomas are accidental discoveries unrelated to the diagnosis or symptoms that led a patient to undergo imaging. And they're becoming more common as more patients get high-resolution magnetic resonance imaging (MRI) and positron emission technology (PET) scans, which can spot abnormalities that once went undetected.

"We know that the diagnosis of incidentalomas can cause patient anxiety and is likely to lead to further investigations and treatment, some of which will be unnecessary, and some of which will cause harm," said lead study author Dr. Jack O'Sullivan of the University of Oxford in the UK.

"Almost all doctors that currently practice will tell you about an experience of an incidental finding," O'Sullivan said. For the current study, O'Sullivan and colleagues analyzed 20 previous research reviews that included a total of 627,073 patients.

Across the studies, the prevalence of incidentalomas varied substantially depending on the type of scan and location in the body, and so did the chance that these abnormalities might be cancer, researchers report in The BMJ, online June 18.

PET scans or CT scans

For example, incidentalomas happened just 2% of the time with certain whole-body PET scans and with chest computed tomography (CT) tests to search for blockages in arteries in the lungs. In these situations, incidentalomas were often found in blood vessels.

With heart and chest CT scans, however, incidentalomas turned up 45% of the time in the throat, abdomen, spine or heart. CT colonoscopy, meanwhile, turned up incidentalomas outside the colon in 38% of cases and brain MRIs caught incidentalomas in the brain 22% of the time.

When patients had incidentalomas in the breast or ovary, they had the highest chance of these abnormalities turning out to be cancer after additional testing, the study found.

About 42% of breast incidentalomas were malignant, as were 28% of incidentalomas in the ovaries and 11% in the prostate. In other cases, the incidentalomas were almost always benign. For example, less than one-hundredth of 1% of incidentalomas in the brain or adrenal gland were cancerous.

One limitation of the study is that researchers did not have enough data to determine the risk of incidentalomas or resulting cancer diagnoses for certain types of tumors and patients.

Even so, the current study adds to evidence linking advanced imaging to a risk of incidentalomas and offers fresh insight into the odds of this happening in various parts of the body, said Dr. Camilla Schalin-Jantti of Helsinki University Hospital in Finland.

"It is well known that continuous improvements in different radiologic imaging techniques that have happened over the last ten years now also show smaller and smaller structures in our bodies that in a majority of cases are harmless," Schalin-Jantti, who was not involved in the study, said.

Incidental findings are also becoming more common as more patients get abdominal, chest and head CT scans performed in the emergency department, Schalin-Jantti added.