"Beverly Hills 90210" star Shannen Doherty has been diagnosed with stage 4 breast cancer, the actor has revealed.

The 48-year-old actor, also known for "Charmed", announced in 2017 that she was in remission for breast cancer that had been initially diagnosed in 2015.

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

The actor said she decided to go public with her diagnosis because the court filings of a legal battle, which she is fighting against an insurance company include her current health status, are set to release this week.

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

Doherty said she has been dealing with the disease in private for more than a year now, while continuing to work, including shooting for the "Beverly Hills" reboot, "BH90210."

She was contemplating her diagnosis while she mourning the death of her "90210" co-star and friend Luke Perry last year.

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

"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," she added.

Doherty said she is yet to come to terms with the return of the disease.

"I don't think that I've processed it. 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."

The actor is married to photographer Kurt Iswarienko.