Dustin Diamond Died of Small Cell Lung Cancer — Here's What to Know About the 'Aggressive' Disease

Dustin Diamond Dead at 44 After Cancer Battle

Dustin Diamond, who played Samuel "Screech" Powers on Saved by the Bell, died Monday morning

On Monday, Dustin Diamond, best known for playing Screech on Saved by the Bell, died of stage 4 small cell lung cancer at age 44. His death came just three weeks after his diagnosis, an unfortunately common problem for this rare disease.

"It's incredibly aggressive," Dr. Nathan Pennell, a medical oncologist specializing in lung cancer at the Cleveland Clinic, tells PEOPLE. "It's one of those cancers that almost always is found by the time it's spread. There really is no early detection for this kind of cancer — it just grows too fast."

Small cell lung cancer is one of the two major types of lung cancer, though it's far more uncommon than the typical type of lung cancer, called non-small cell lung cancer. It "almost always a disease of people who are lifelong, heavy smokers," Pennell says, which makes Diamond's case even rarer. The actor's longtime manager Roger Paul told PEOPLE that "Dustin wasn't a smoker."

Noel Vasquez/Getty Dustin Diamond

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"About 2 to 3% of people who get small cell lung cancer have never smoked," Pennell says, "so that actually makes it quite an unusual circumstance, though lung cancer generally in people who have never smoked is actually becoming much, much more common."

Pennell says the "major risk factor" of small cell lung cancer is tobacco smoke, but for those who haven't smoked, radon gas, which can be found in basements if they're not treated for it; industrial pollution and in extremely rare cases, family history, can all be causes.

As with all cancers, the best chance of survival for small cell lung cancer is if it's caught early. The problem, though, is that it's hard to identify until after its already fairly advanced.

"About two-thirds of people have stage 4 when small cell lung cancer is found, and almost everyone else has stage 3," Pennell says. The symptoms to look for are coughs that don't go away, sometimes with bleeding, feeling weak or tired, weight loss, hoarseness of voice and sometimes swelling in the face and arms.

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In Diamond's case, he was "feeling out of sorts and he'd had a lump on his neck that he was ignoring," Paul said, but worried about going to the hospital. Pennell emphasizes that "it's critically important that no one blame Mr. Diamond for what happened to him."

NBC Dustin Diamond on Saved by the Bell

"A 44-year-old who's never smoked, if they were coughing or something else, it would almost always be benign and something that would just get better," he says.

Diamond's age makes him "very young" for this type of cancer. "The average age for someone with small cell lung cancer would be about 70," Pennell says. "But the range of people who get cancer is extremely wide, especially in non-smokers with lung cancer. They're very commonly younger, in their thirties, forties, and fifties. The truth is, anyone with lungs can get lung cancer and we really need a better way of detecting it, especially in younger people who don't have the traditional risk factors like smoking."

Detection is essential to having a chance to save lives, because once it becomes stage 4, "those patients we cannot cure, and we're really just trying to help them live longer." With most patients, because the cancer is so fast-acting, treatment begins the moment they're diagnosed with chemotherapy, radiation or immune therapy drugs, a newer advancement against the disease.

"We know that we have a very short window of time, because they get sick so quickly," Pennell says. "The blessing of small cell is that most people will respond to treatment and feel much better with chemotherapy. But the curse is that the treatment is temporary, and the cancer becomes resistant to treatment."

Mario Lopez/Instagram Dustin Diamond and Mario Lopez

Most patients with stage 4 small cell lung cancer only live another year, on average, and often less, in Diamond's case.

"As this so poignantly illustrates, without treatment or if people are too sick to get treatment, oftentimes they only live weeks or a few months with small cell lung cancer," Pennell says.

Pennell encourages people with symptoms — like a cough that won't go away — to see a doctor and get checked out, just in case. He adds that the COVID pandemic may have scared people off from seeking medical help, a "major problem."

"It's very important that we message out that if you are sick and you are worried, it's very safe to come to the doctor now," he says. "We have lots of good safety measures in place to prevent people from getting COVID and almost no one gets COVID from a medical facility, they're getting it from their families and surroundings and not there."