Patients learning they have a "spot" on their lung often assume they have cancer, according to a new study - but that's usually not the case.

Researchers say doctors could do more to help patients understand what happens when a "spot," or nodule, is found on a CT scan or chest x-ray, and what it means for their long-term health.

"On a CT (scan) we see them all - all the tiny little details and all the tiny nodules on the lung, and 99 percent of those are nothing, are not cancer," said Dr. Heidi Roberts, a radiologist and lung cancer specialist from Women's College Hospital in Toronto.

Non-cancerous nodules can be a result of scarring in the lungs, an infection or an inflammatory response initiated by the immune system, researchers said.

According to the American Cancer Society, about 226,000 new cases of lung cancer will be diagnosed in 2012 and 160,000 people will die of the disease.

Recent recommendations from the American College of Chest Physicians and the American Society of Clinical Oncology call for annual screening using CT scans for current and former heavy smokers age 55 to 74.

But another group, the government-backed U.S. Preventive Services Task Force, says the evidence is too limited to recommend for or against screening.

Chest CTs are also done to check for pneumonia or blood clots in the lungs or in people who have trouble breathing and chest pain.

For the new study, researchers organized focus groups for 22 adults who had lung nodules that hadn't been definitively diagnosed as cancerous or non-cancerous. They asked the patients about their experiences talking with primary care doctors and lung specialists when the abnormality was caught.

Dr. Renda Soylemez Wiener of the Boston University School of Medicine and her colleagues found almost all patients immediately assumed they had cancer when they were told about the nodule.

In reality, the researchers reported in the journal Chest, after a couple years of check-ins typically less than one in 20 nodules turns out to be cancerous.

Most patients said they wanted doctors to use common, uncomplicated terms when describing the nodule, to draw them a picture or use the scan to show them how big it was and to estimate their chances of actually having lung cancer.

"A lot of times doctors kind of feel, we see pulmonary nodules so commonly that it seems like this is not a really big deal," Wiener told Reuters Health.

She and her colleagues also recommended doctors explain to patients why they might not order a biopsy - and when, if ever, patients would need one.

When they're first caught, lung nodules are often too small to be biopsied.

Typically, people with a newly-spotted nodule will be asked to come back after a few months for another CT scan.

If the nodule has grown, doctors might order a biopsy to check for cancer. But if it hasn't gotten any bigger after two or three years of follow-up, doctors will assume it's not cancerous.

"If you want to biopsy all the nodules that are in the lung, it's just diagnostic overkill," Roberts, who wasn't involved in the new study, told Reuters Health.

She compared lung nodules to moles on the skin: Lots of people have them, but they're typically not worth checking out unless they look unusual or are growing.

"There might be some that look a little bit more suspicious than others, but if it's a small nodule, we still would do the same follow-up," Roberts said.

The study was published in journal Chest.