Last week, comedian Kathy Griffin revealed that she was diagnosed with stage 1 lung cancer and is expected to undergo surgery to remove half of her left lung.

The 60-year-old went on to say, “Yes, I have lung cancer even though I’ve never smoked!”

The majority of lung cancer diagnoses occur in people who smoke, but some patients who are non-smokers may also develop the disease.

Dr. Nathan Pennell, a lung cancer specialist, told PEOPLE, “It’s a lot more common than people realize.”

Dr. Pennell is the director of the TCI Lung Cancer Medical Oncology Program at The Cleveland Clinic’s Taussig Cancer Center.

He explained that of nearly 200,000 Americans are diagnosed with lung cancer each year, and of them, around 10% of the men and 15% of the women have never smoked.

Dr. Pennell said researchers are unsure if the rise in lung cancer cases among non-smokers is because “it’s truly more common and more people are getting it, or whether it’s just a higher percentage of people with lung cancer are non-smokers because fewer people are smoking.”

“Less than 15% of adults in the U.S. are smoking now, which is fantastic, so a higher percentage of the cases of lung cancer in the last five or six years are in non-smokers,” he added.

However, he said, in general, “the only thing you need in order to get lung cancer is lungs.”

It is still unclear how non-smokers develop lung cancer, but Dr. Pennell said, “there are a number of risk factors other than tobacco for lung cancer.”

“There’s definitely some component of family history,” he explained.

“Radon, which is a colorless odorless gas that is in most people’s basements in the United States, is probably the second biggest risk factor for lung cancer behind tobacco,” he added. “That’s something that everyone tests for now when they sell a house, but for older people, it wasn’t routinely tested for when they were growing up and they could have been exposed to that. And industrial pollution and other things like heavy metals certainly can play a role as well.”

It is difficult to diagnose lung cancer in people who do not smoke, although there are screening tests that are only used for those who smoke.

Dr. Pennell said, “We have screening CT scans, but that’s only for people who have smoked at least 30 packs a year and are over age 50. For people who have smoked less than that, or have never smoked, there’s no screening.”

“Luck” is one of the factors when it comes to diagnosing lung cancer in non-smokers, the oncologist said.

Dr. Pennell noted, “If they go into the emergency room because they had a bike accident or a car accident and get scans, doctors could spot a nodule in their lungs.”

Otherwise, people may develop a bad or bloody cough, which would be an indication of lung problems, but “unfortunately, most of the time when you develop symptoms from your lung cancer, it’s more advanced at that point and harder to cure.”

Fortunately, Griffin had that “luck” on her side, as her doctors diagnosed her lung cancer in an early stage during a regular checkup.

Her cancer has not spread outside the lungs and for that, she typically needs a “lobectomy,” which means removing a part of the lung, according to Dr. Pennell.

He said, “Doctors will usually remove the complete lobe of the lung where the tumor is, leaving you with the other half still to breathe. And in non-smokers, especially, typically you can survive just fine on three-quarters of your lungs.”

Dr. Pennell explained that a lobectomy is a minimally invasive surgery and has “very short recovery times.”

“Oftentimes people are only in the hospital for 48 hours and within a month they feel seventy-five percent better,” he added. “And within three months they feel, more or less, a hundred percent again. People can even live with one lung, honestly. Especially if they’re healthy.”

Dr. Pennell wants everybody to understand that people who do not smoke may also get lung cancer.

He said, “It’s a lot more common than people realize. And we do need to do a lot more research in order to try to help screen for that, because right now there really is no way of identifying lung cancer in non-smokers other than again, by luck.”