Former "Beverly Hills, 90210" star Shannen Doherty has given her Instagram followers a sobering look at her ongoing battle with stage 4 breast cancer.

Sharing a video from January that shows her getting fitted with a face mask used for radiation treatment for brain cancer, Doherty explained on Instagram Tuesday that a CT scan "showed Mets in my brain," meaning cancer cells had migrated there.

"January 12, the first round of radiation took place. My fear is obvious. I am extremely claustrophobic and there was a lot going on in my life," she explained in a separate post, writing that she is "fortunate" to have "great" doctors and "amazing" techs looking out for her.

She added, "But that fear…. The turmoil….. the timing of it all…. This is what cancer can look like."

Doherty was first diagnosed with breast cancer in 2015. After entering remission, she revealed in 2020 the disease had spread and returned as stage 4.

In an interview with "Good Morning America" at the time, the "Charmed" actress said the diagnosis was "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 besides me deserves this? None of us do,'" she said.

In 2021, Doherty told ABC News, "I'm going to keep fighting to stay alive."

"You really have to dig deep to face cancer, and in that you find all the stuff that you had hidden away," she said.