Appearing on ABC News Tuesday, the 48-year-old actress said she now has stage 4 breast cancer.

"It's going to come out in a matter of days or a week that I have stage 4," Doherty said. "So my cancer came back and that's why I'm here."

The "Beverly Hills 90210" star announced in 2017 that she was in remission for breast cancer that had been initially diagnosed in 2015.

For more than a year now, Doherty said, she has been quietly battling cancer again, even while continuing to work , including filming the "Beverly Hills" reboot, "BH90210."

She was dealing with the devastating news while mourning the death of her former "90210" costar Luke Perry in 2019.

"It was so weird for me to be diagnosed and then somebody who was seemingly healthy to go first," she said. "It was really shocking and the least I could do to honor him was do that show. I still haven't done enough in my opinion."

She continued: "It's a hard one because I thought when I finally do come out, I would have worked and worked 16 hours a day and people can look at that and say, 'Oh my God, she can work and other people with stage 4 can work. Our life doesn't end the minute we get that diagnosis. We still have some living to do."

Doherty said she is having trouble processing that the disease returned.

"I don't think that I've processed it," she said. "It's a bitter pill to swallow in a lot of ways. I definitely have days where I say, 'Why me?' And then I go, 'Well why not me? Who else? Who else beside me deserves this?' None of us do. I would say that my first reaction is always concern about how am I going to tell my mom, my husband."

She has been married to photographer Kurt Iswarienko since 2011.

EXCLUSIVE: @DohertyShannen opens up about her private health battle. "I'm stage four -- my cancer came back." https://t.co/Xk9QEWWgVD — Good Morning America (@GMA) February 4, 2020

Doherty said she decided to share her diagnosis because court filings set to release this week in a legal battle she has with an insurance company include her current health status.

"I'd rather people hear it from me," she said.