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Olivia Munnwas diagnosed with breast cancer in 2023 and chose to keep the news private for a year. In an open letter shared on Instagram in March 2024, the former The Newsroom star detailed how her luminal B cancer was discovered and explained why she decided to keep the information private until now. Since then, Olivia has been keeping fans updated on her journey, aiming to raise awareness about the type of cancer, which is the most common form of cancer in women in the United States, excluding skin cancers.
Get an update on Olivia’s health and learn more about her breast cancer diagnosis below.
Olivia Munn Was Diagnosed With Luminal B Cancer
On March 13, 2024, the X-Men: Apocalypse star recollected the moment when her cancer was discovered in an Instagram post.
“In February of 2023, in an effort to be proactive about my health, I took a genetic test that checks you for 90 different cancer genes,” Olivia began.”Two months later, I was diagnosed with breast cancer. … In the past ten months, I have had four surgeries, so many days spent in bed I can’t even count…surprisingly, I’ve only cried twice. I’ve tended to let people see me when I have energy, when I can get dressed and get out of the house, when I can take my baby boy to the park. I’ve kept the diagnosis and the worry, and the recovery and the pain medicine, and the paper gowns private.”
Olivia’s reason for withholding the cancer diagnosis from the public was because she “needed to catch [her] breath and get through some of the hardest parts before sharing.”
“I wouldn’t have found my cancer for another year — at my next scheduled mammogram — except that my OBGYN, Dr. Thais Aliabadi, decided to calculate my breast cancer risk assessment score,” Olivia continued, adding, “The fact that she did saved my life.”
After looking through various aspects such as family cancer history and giving birth to a child over the age of 30, the doctor determined that Olivia’s “lifetime risk” was 37 percent.
“Because of that score, I was sent to get an MRI, which led to an ultrasound, which then led to a biopsy,” Olivia explained. “The biopsy showed that I had luminal B cancer in both breasts. Luminal B is an aggressive, fast-moving cancer. Thirty days after that biopsy, I had a double mastectomy. I went from feeling completely fine one day to waking up in a hospital bed after a 10-hour surgery the next.”
Olivia also noted that she is “lucky” because she and her doctor “caught it with enough time that [she] had options.” At the end of her message, Olivia noted, “I want the same for any woman who might have to face this one day.”
What Is Luminal B Cancer?
According to City of Hope’s cancercenter.com, luminal B is “expresses estrogen or progesterone (or both) hormone receptors (HR)” and “doesn’t express human epidermal growth factor receptor 2 (HER2) proteins.”
The website also notes that the two types of breast cancer, luminal A and B, differ because B “expresses the HER2 protein, which may quicken the growth of cancer cells. As a result, luminal B breast cancer is typically more aggressive and receives a higher grade and a poorer prognosis than luminal A.”
How Is Olivia Munn Doing Now?
Olivia has undergone several surgeries, including a double mastectomy and hysterectomy. She also went through hormone suppression therapy and froze her eggs.
Alongside her health journey, Olivia has been raising her two children with her husband, John Mulaney. The couple welcomed their son, Malcolm Hiệp Mulaney, in November 2021, before her breast cancer diagnosis. They later expanded their family with the arrival of their second child, daughter Méi June Mulaney, in September 2024 via surrogate.
In February 2025, Olivia shared that while she still has “years to go” in her breast cancer treatment, she’s feeling healthy. At TIME’sWomen of the Year gala, Olivia proposed a toast “to good health [and] to healthy days,” and shared a touching story about her daughter Méi, who had been suffering from “a lot of discomfort” and stomach pains. Trusting her “mother’s intuition,” Olivia switched Méi’s formula, and within hours, her daughter started feeling better.
“It’s one of my most proud moments as a mother,” Olivia said. “She was smiling and she was healthy, and then I realized that I’d felt pretty good all day too. I have years to go in my cancer treatment, but on that Friday my joints didn’t ache, and I wasn’t too hot or too cold from going into a surgical menopause, and my brain fog had cleared, at least for that day anyway … As I held my daughter, I was so grateful that I was healthy enough to see every minute of it all.”
Despite her health challenges, Olivia has attended several public events over the past couple of years. She was at the 2024 Oscars in Los Angeles, just days before announcing her cancer diagnosis, and has walked red carpets with John, including at the SNL 50: The Anniversary Special.
Olivia has also made it a point to continue the conversation about breast cancer. She’s appeared on various television shows to encourage other women to get checkups.
