'Big Bang Theory' Star Kate Micucci Reveals Lung Cancer Despite Never Smoking—How Can That Happen?

Fact checked by Nick Blackmer

• Actress Kate Micucci, 43, has lung cancer, according to a recent TikTok video she shared with her followers.

• Micucci said the diagnosis was a “surprise” because she’s “never smoked a cigarette in [her] life.”

• Though the majority of lung cancers occur in people who smoke or who have smoked, approximately 20% of lung cancers occur in nonsmokers.

Kate Micucci, known for her work on “The Big Bang Theory,” has lung cancer, according to a TikTok video shared Tuesday with her followers.

“Hey everybody, this is not a TikTok, it’s a ‘sick tok,’” Micucci, 43, told viewers. “I’m in the hospital but it’s because I had lung cancer surgery yesterday.”

Micucci said her care team found the cancer early—but that it was still an unexpected discovery. “It’s pretty weird because I’ve never smoked a cigarette in my life,” she said, “so it was a surprise, but also I guess it happens.”

Though smoking is the leading risk factor for lung cancer—about 80% of lung cancer cases are caused by smoking—a growing number of diagnoses are in people who haven’t smoked.

The Centers for Disease Control and Prevention (CDC) estimates that as many as 20% of lung cancers diagnosed in the U.S. each year are in people who have never smoked, or who have smoked fewer than 100 cigarettes in their lifetimes.

“This is a very disturbing problem,” Lary Robinson, MD, a lung cancer specialist and thoracic surgeon at Moffitt Cancer Center, told Health. “Twenty years ago, a case of lung cancer in a never-smoker would have been a reportable case—we never saw it. But I’ll see at least one case a week now.”

Women may also be bearing the brunt of these lung cancer diagnoses: Research published earlier this year showed that lung cancer incidence rates are higher in younger and middle-aged women compared to men of the same age—and experts don’t yet know why.

Here’s what to know about lung cancer in nonsmokers, including how it differs from cancer caused by smoking.

Why Might Someone Who Never Smoked Get Lung Cancer?

Smoking cigarettes, pipes, or cigars are the main risk factors for lung cancer, but they aren’t the only ones: Other risk factors include secondhand smoke, radon, air pollution, asbestos, and having a family history of lung cancer.

Of those additional risk factors, researchers estimate that secondhand smoke contributes to about 7,300 lung cancer diagnoses each year, while radon contributes to about 2,900 cases.

But the reasons for the increase in lung cancer cases among nonsmokers have yet to be pinpointed. Radon, for example, has been a known risk factor for years. “People aren’t getting exposed to more radon than they were 50 years ago,” said Robinson. “I think the cause is going to turn out to be something environmental.”

But there’s much more research to be done—particularly regarding lung cancer incidence rates in women who have never smoked.

“We’re currently looking at causes from estrogen metabolites, chronic inflammation, processed foods, and chemicals,” Jack Jacoub, MD, a board-certified medical oncologist and medical director of MemorialCare Cancer Institute at Orange Coast and Saddleback Medical Centers in Orange County, California, told Health. “But we’re not sure about all of these things and how they come together to increase lung cancer risk.”

Lung Cancer in Smokers vs. Nonsmokers

Lung cancer in nonsmokers is typically different than lung cancer in people who smoke—for nonsmokers, lung cancer tends to develop when a person is younger, and the cancer itself may have certain gene changes that are different from smokers’ tumors.

Nonsmokers are usually diagnosed with non-small cell lung cancers, namely adenocarcinoma, which accounts for 50%–60% of those lung cancers. This type of cancer starts in the lungs’ mucus-producing cells. Adenocarcinoma is often found on the outer parts of the lung, which makes it easier to diagnose before it has spread.

Another 10%–20% of lung cancers in people who have never smoked are squamous cell carcinomas—cancers that form in the cells that line the inside of the lungs’ airways.

Though the types of cancers smokers and nonsmokers tend to get may be different, the symptoms are generally the same and include:

• Feeling generally unwell

• Unexplained fatigue

• Unexplained weight loss

• Frequent coughing

• Hoarseness

• Coughing up blood

• Chest pain

• Wheezing

• Shortness of breath

The prognosis for a nonsmoker diagnosed with lung cancer depends, like most cancers, on whether it was found early or in later stages.

Because it’s not recommended for nonsmokers to undergo lung cancer screenings, it’s possible that cancer in some nonsmokers will be diagnosed at later stages, leading to an unfavorable outcome.

However, if lung cancer is detected early in a nonsmoker, they have a better chance of survival. “[Lung cancer in nonsmokers] tends to occur in healthier, younger people,” said Jacoub. “They don’t have a lot of the smoking-associated chronic illnesses like heart disease and lung disease.”

Nonsmokers with lung cancer may also benefit from the mutations that may have led to their cancers. “The saving factor for many never-smoking patients with lung cancer is that they tend to have mutations that we have drugs for,” said Robinson. “We have a lot of targeted agents to help.”

Lung Cancer Prevention for Nonsmokers

More research is needed to determine what’s causing lung cancer in people without a history of smoking.

Researchers believe staying away from secondhand smoke, air pollution, radon, and other cancer-causing agents (asbestos, arsenic, diesel exhaust) can help reduce nonsmokers’ risk of lung cancer.

More general cancer prevention methods may help, too, though they’re not guaranteed.

“I could stand on my soapbox and say the best thing to do to lower your risk of lung cancer if you don’t smoke is to maintain a normal weight, eat a healthy diet, and exercise,” said Robinson. “If you did that, you would lower your risk of a lot of different cancers and diseases, but that’s not a guarantee.”

Some risk factors, however—like a personal or family history of the disease—cannot be changed. It’s for this reason that experts recommend everyone know or become aware of their family history, which can also be a preventative measure.

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