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Olivia Munn reveals new details about breast cancer journey: ‘Nothing could prepare me’

The 43-year-old actress revealed she was diagnosed with breast cancer in March.
/ Source: TODAY

Olivia Munn is still dealing with the effects of being diagnosed with breast cancer last year and the subsequent treatment she endured to keep her as healthy as possible.

The former star of "The Newsroom" first shared her diagnosis with the public in a March 13 Instagram post. In her first interview since, Munn spoke to People magazine exclusively about her cancer journey.

“I was walking around thinking that I had no breast cancer,” she told the magazine. “I did all the tests that I knew about.” 

“You realize cancer doesn’t care who you are; it doesn’t care if you have a baby or if you don’t have time,” Munn added. “It comes at you, and you have no choice but to face it head-on.”

Oliva Munn diagnosed with breast cancer

Munn revealed her breast cancer diagnosis in an Instagram post on March 13, writing, “I hope by sharing this it will help others find comfort, inspiration and support on their own journey.”

In the post, Munn explained she was diagnosed with luminal B breast cancer in April 2023 after undergoing a course of genetic tests. At first, she tested negative for the BRCA gene, a mutation commonly linked to breast cancer, and had a clear mammogram.

But when Munn went to see her OB-GYN for her annual pap smear, her doctor calculated her breast cancer risk assessment score and determined she had a 37% lifetime risk of having breast cancer.

So, Munn underwent an MRI, an ultrasound and a biopsy. An MRI found a spot near one of her lymph nodes in her right breast, Munn told People. The ultrasound that followed found two more tumors in her right breast, which turned out to be stage 1 cancer. And after reviewing her first MRI again, doctors confirmed cancer was in her left breast, too.

During surgery, her doctors also found a “tangerine-sized” pre-invasive cancer, Munn told People.

She was set to head to Germany to start shooting a sci-fi film when she found out. “I was not someone who obsessed over death or was afraid of it in any way,” she told People. “Having a little baby at home made everything much more terrifying.”

What is luminal B cancer?

Munn said she had luminal B cancer in both breasts, which she described as “an aggressive, fast moving cancer.”

Doctors and researchers categorize cancer into groups according to genetic information, per the Mayo Clinic. Luminal B breast cancer is estrogen receptor-positive, which means the cancer cells rely on estrogen to grow. So, if estrogen production is stopped with treatment, the cells will ideally stop growing too, according to the National Cancer Institute.

Luminal B is also typically HER2 negative. HER2 is the protein that helps breast cancer cells grow, per the American Cancer Society. When it's negative, that means the cancer isn't likely to respond to drugs that target HER2.

You can also expect luminal B cancer to be progesterone receptor-negative, meaning it won't respond very well to hormone therapy.

"About 15-20% of breast cancers are luminal B tumors," according to Susan G. Komen. "Women with luminal B tumors are often diagnosed at a younger age than those with luminal A tumors."

What is a breast cancer risk assessment?

If it weren’t for her OB-GYN, Dr. Thaïs Aliabadi, Munn said she wouldn’t have been diagnosed for another year. Last year, Aliabadi recommended Munn have her breast cancer risk assessment score calculated. “The fact that she did that saved my life,” wrote Munn.

“A breast cancer risk assessment score is calculated using a mathematical model that incorporates various risk factors that have been shown to be associated with breast cancer,” Dr. Jennifer Plichta, director of the Breast Risk Assessment Clinic at Duke Cancer Institute, previously told

It can determine your lifetime risk of developing breast cancer and your risk of invasive breast cancer, meaning it spreads outside the milk ducts, of the next five years.

There are at least 24 risk assessment models used to determine someone’s score, according to the Cleveland Clinic. But the most common is the Gail Model which looks at demographic information such as age, race and biopsies, among other considerations. Your doctor can calculate your score for you or you can calculate it using an online tool such as this one from the National Cancer Institute.

Munn and Aliabadi used the free online tool called a Tyrer-Cuzick risk assessment calculator, per People.

Had Munn delayed any longer, Aliabadi said the cancer would have likely grown and "she probably wouldn’t have been early stage."

Munn urged her followers to ask their doctors to assess their likelihood for developing breast cancer. Aliabadi said that if someone's score is higher than 20%, they need annual mammograms starting at 30 years old. Aliabadi also said that she's calculated breast cancer risk for patients as young as 25.

"I want every woman to be their own self advocate at home," Aliabadi said. A mammogram, she added, won't always be enough. "My heart aches when I see these young patients with stage 4 breast cancer," she said, because she believes they could have caught it earlier had they had an assessment.

It's worth noting that the risk assessment tools are population-based and can only determine your average risk among those in your demographic, previously reported. It can’t provide a prediction about whether you'll have breast cancer or not.

What treatment did Olivia Munn have?

Within 30 days of being diagnosed, Munn underwent a series of surgeries. She had "a lymph node dissection, a nipple delay procedure (a surgical procedure which spares the nipples) and a double mastectomy,” when both breasts are removed to reduce the risk of cancer recurring, People reported.

“There’s so much information, and you’re making these huge decisions for the rest of your life,” Munn told People. “I really tried to be prepared, but the truth is that nothing could prepare me for what I would feel like, what it would look like and how I would handle it emotionally. It was a lot tougher than I expected.” 

In her Instagram post, Munn described having four surgeries in the past 10 months.

“I had amazing doctors, but it was still a negotiation sometimes on what we are doing,” she told People. She could have opted out of the nipple delay, which saves the nipples, but chose to go forward with it. “But I’m glad I did. I want to give myself the best shot of keeping the parts of me that I can keep.”

She underwent her breast reconstruction last fall and decided to make her breasts smaller than they were before.

"I know a lot of women want to go bigger, but (I said) go smaller,” she told People. “It’s so important to say what you want out loud — and don’t stop. Even as the anesthesia was making its way into my body, the last thing I said was ‘Please go smaller.’"

So far, Munn hasn't had to undergo chemotherapy or radiation, but in November 2023, she began hormone suppression therapy to lessen the likelihood that the cancer would return, People reported.

But the therapy has put Munn into medically induced menopause, which has brought on several symptoms. “I’m constantly thinking it’s hot, my hair is thinning and I’m tired a lot,” Munn told People.

Since her diagnosis, Munn wrote that she’s “learned more about cancer, cancer treatment and hormones,” than she could have imagined. And she thanked family, friends and the breast cancer patients she’s connected with over the past year for their support.

She also wrote about being thankful to partner John Mulaney “for the nights he spent researching what every operation and medication meant and what side effects and recovery I could expect.” And she expressed her gratitude for his being there when she went into and came out of surgery.

“It would’ve felt like climbing an iceberg without him,” Munn told People. “I don’t think he had a moment to himself, between being an incredibly hands-on father and going to and from the hospital — taking Malcolm to the park, putting him to nap, driving to Cedars-Sinai, hanging out with me, going home, putting Malcolm to bed, coming back to me. And he did it all happily.”

Munn gave a glimpse at her treatment in a video she shared on Instagram. In it, Aliabadi hugged Munn in a hospital bed and dressed in a surgical gown and cap, and Aliabadi told Munn to do this for her son before Munn said, “I’m ready.”

Despite being diagnosed with cancer so young, Munn said she feels "lucky."

“We caught it with enough time that I had options,” she wrote. “I want the same for any woman who might have to face this one day.”