Actor Olivia Munn has revealed she has had a double mastectomy after being diagnosed with breast cancer.

Munn thanked her doctors and urged fans to do their own risk assessment, after revealing her diagnosis in an Instagram post on Wednesday (US time).

“I’m lucky. We caught it with enough time that I had options. I want the same for any woman who might have to face this one day,” the 43-year-old actor posted, along with photos and a video of her being treated at a hospital.

Munn said she took a genetic test in February 2023 that checked for 90 different cancer genes. It was negative for all.

Even so, her doctor decided to calculate her Breast Cancer Risk Assessment Score and that “saved my life”, Munn wrote.

After recording a high score, Munn had imaging tests and then got a biopsy, which found she had an aggressive form of cancer in both breasts. She had a double mastectomy 30 days later, and has had four surgeries in all in the past 10 months.

She said she kept it private because: “I needed to catch my breath and get through some of the hardest parts before sharing.”

Munn thanked family and friends, especially her partner, comedian John Mulaney, “for being there before I went into each surgery and being there when I woke up, always placing framed photos of our little boy Malcolm so it would be the first thing I saw when I opened my eyes.”

One of her doctors, who was mentioned by name in Munn’s post, described the actor as her “hero”.

“Your post will save so many lives. I love you so much,” Dr Thais Aliabadi wrote, signing off with a heart emoji.

There was also support for the star from other actors, including Jessica Chastain.

“You are very generous to share your story. I believe in doing so, you’ve saved lives. So much love to you and your family,” she wrote.

TV journalist and presenter Katie Couric said she had been thinking about Munn.

“Maybe this is why. Sending you love and gratitude for sharing this. And a huge virtual hug,” she wrote.

Munn was a correspondent on The Daily Show with Jon Stewart. Her movie credits include Magic Mike, The Predator, Office Christmas Party and X-Men: Apocalypse.

She also had a three-year role in HBO’s The Newsroom.

-with AAP