“Falcon Crest S”tar“ ”Susan Sullivan on Lung Cancer Surgery and ‘Painful’ Recovery: ‘I Didn’t Want to Give Up’ (Exclusive)

The actress, 81, had the upper lobe of her right lung removed after being diagnosed with lung cancer

Falcon Crest star Susan Sullivan is speaking out about her lung cancer diagnosis, hoping to raise awareness of the growing threat of the disease among young women.

In an exclusive interview with PEOPLE, Sullivan, 81, shares how her lung cancer journey began in September after going to her doctor for a routine mammogram. The actress, who's appeared in more than 70 shows and TV movies, including starring roles in Another World and Castle, says during the appointment the radiologist noticed a swollen lymph node under her arm and suggested a biopsy.

“This is unfortunately who I am: I went, ‘I don’t think it’s anything. I don’t need a biopsy,’ ” Sullivan, who wasn't a smoker, says.

Luckily her partner of 35 years, psychologist and writer Connell Cowan (co-author of the self-help classic Smart Women, Foolish Choices) had a different response.

“He said, ‘Are you crazy? When I had an enlarged lymph node, I thought I had cancer,’ ” Sullivan says.

“When he said those words, I went, ‘Oh f---. I have lung cancer.’ ” Both her father and uncle died of the disease.

Related: Former Castle Actress Susan Sullivan Diagnosed with Lung Cancer: 'Healing Process Is a Struggle'

Before going in for CT and PET scans, Sullivan wrote herself a note that read, “Have lung cancer. It’s going to be okay though. Don’t worry about it. Just take care of it.”

Days later, she received the diagnosis of non-small cell lung cancer. Surgery was scheduled for Oct. 11 at Cedars-Sinai in Los Angeles, where doctors removed the upper lobe of her right lung and drained lymph nodes as well.

"I thought it was going to be pretty simple that they just take that one little nodule, but they took the whole upper part of my lung," Sullivan says. "My surgeon said when they went in and looked around with their two cameras, that it would be better to take it all out so any potential for this coming back would be eliminated, which is what they did."

"So now the cancer is completely gone. I am cancer-free, which is an enormous blessing because you don't want to have to go through endless chemotherapy afterward," she adds.

Following the surgery, Sullivan posted a photo on X, formerly known as Twitter. In the post she is wearing a yellow mask and a hospital gown and is holding an IV pole. The post received almost 460 comments from her fans.

“Suddenly all of these people I haven’t spoken to or heard from in years got in touch with me!” she says of her reaction to the post. “It was sort of a strange reverse gift."

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Five days after the surgery, Sullivan was up and walking. Since then, she says, she's been working on her strength and has started to exercise.

Through it all she has tried to remain positive, even in moments when all she wanted to do was lie in bed. “I didn’t want to fade out like that. So I got stronger,” she says.

Related: More Adults Should Be Screened for Lung Cancer Under New Guidelines from the American Cancer Society

Dr. Clark Fuller, Sullivan's thoracic surgeon who's leading the Women’s Lung Cancer Initiative at Cedars-Sinai, tells PEOPLE that since Sullivan was so active, the surgery shouldn’t affect her ability to do the things she enjoys.

"For a long time, lung cancer had a stigma of, ‘You did it to yourself.’ That’s just not so anymore,” he says.

"The demographics have changed in women. We see it at a younger age; we see it more associated with a family history. And we see it with less — if not a lack of — a smoking history,” he adds.

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