(NEXSTAR) – Last month, actress and comedian Kate Micucci revealed that she had been diagnosed and treated for lung cancer despite “never” having smoked a cigarette in her life.

“It was a surprise, but also, I guess it happens,” the “Big Bang Theory” actress said, shortly before confirming she had undergone treatment and is now “cancer-free.”

News of Micucci’s diagnosis came as a shock to followers, especially considering she’s a non-smoker. But like Micucci said, this kind of thing “happens” more frequently than most of us likely imagine.

A 2020 research paper co-authored by Ahmedin Jemal, the senior vice president of the Surveillance & Health Equity Science Department of the American Cancer Society, found that approximately 12.5% of lung cancer patients in a wide-ranging study supported by CDC data were classified as “never-smokers” — a designation given to patients who were not only non-smokers but hadn’t been regular smokers at any previous time.

“Even among never-smokers, lung cancer, because it is very common … is a top 10 leading cause of cancer deaths,” Jemal told Nexstar.

Lung cancers in never-smokers, he said, could stem from a variety of environmental factors, the biggest being secondhand smoke, radon poisoning, pollution, exposure to asbestos, and exposure to arsenic in drinking water. This also means that the type of cancer-causing mutations that develop in never-smokers can be different than the kinds that develop in smokers.

“Lung cancer encompasses two primary categorizations: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC),” Sean Marchese, a registered nurse at The Mesothelioma Center, told Nexstar. These categories have subtypes, and the treatment approach may vary based on the specific type and stage of the cancer.”

According to the Centers for Disease Control and Prevention, the most common type of cancer afflicting never-smokers is adenocarcinoma, a non-small cell lung cancer that accounts for between 50% and 60% of cases.

Treatment, as Marchese said, may differ between the types of cancer and where it’s identified in the lung, but experts generally agree that the lung cancers most often associated with never-smokers are easier to treat, using a combination of procedures including surgery, radiation, chemotherapy, immunotherapy, or newer targeted therapies.

“The proportion of lung cancer cases that have the genetic mutation that can be treated with new therapy is higher among never-smokers than in smokers,” Jemal said.

On its website, a thoracic surgeon for Yale Medicine likened a smoker’s cancer to a black marble and a never-smoker’s to a speck of black sand.

“Instead of a spot or a lump, it’s more like a hazy area. It’s more diffuse,” said Daniel Boffa, MD, also the clinical director at Yale’s Center for Thoracic Cancers.

Cancer in never-smokers also grows less rapidly, and is less likely to spread than cancer in smokers, Boffa noted.

Jemal warned, however, that lung cancer — in smokers and never-smokers alike — is often fatal. And while a small percentage of these cancers can be eradicated completely, “recurrence is common.”

“People say, ‘I’m cured,’ but then it will come back,” Jemal said. “It can recur after three, four years.”

Those at the highest risk of developing lung cancer or having cancer recur can plan routine screenings with their doctors. But for the rest, prevention is key.

In smokers, experts say the best thing to do is quit. (“Those who quit at any age — at any age — reduce the risk of developing cancer,” Jemal said.) But for non-smokers, reducing risk means limiting exposure to secondhand smoke, testing your home’s radon levels, or avoiding air or water pollutants.

As the American Cancer Society says, however, lung cancer can sometimes develop in people with inherited DNA mutations, or from other “random events that don’t have an outside cause.” It’s these factors that make lung cancer tricky to predict in non-smokers, making early detection all the more important.

“While many cases are preventable, some risk factors are unavoidable,” Marchese told Nexstar.