The 43-year-old actress, known for her roles on The Newsroom, The Daily Show with Jon Stewart and the X-Men franchise, revealed her health news in an Instagram post today. She says she hopes that by sharing the news, “it will help others find comfort, inspiration and support on their own journey.

Munn writes that in February 2023, “in an effort to be proactive” about her health, she took a genetic test that checks for cancer genes: she tested negative for all of them, including BRCA, the most well-known breast cancer gene.

She said she also had a regular mammogram that same winter. It would’ve been natural to assume she was in the clear — but just two months later she got some unexpected news.

Munn’s OBGYN, Dr. Thaïs Aliabadi, calculated her Breast Cancer Risk Assessment Score, which includes factors like age and family breast cancer history. The doctor found her lifetime risk to be high at 37%.

“Because of that score I was sent to get an MRI, which led to an ultrasound, which then led to a biopsy,” Munn wrote. “The biopsy showed I had Luminal B cancer in both breasts,” she wrote, calling it an “aggressive, fast moving cancer.”

Munn notes that she likely wouldn’t have discovered the cancer for another year at her next scheduled mammogram, so the doctor’s test likely saved her life. She urged other women to ask their doctors to calculate their own risk scores.

“I’m lucky,” Munn wrote. “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.”

Thirty days after the diagnosis, Munn had a double mastectomy. “I went from feeling completely find one day, to waking up in a hospital bed after a 10-hour surgery the next.”

The actress wrote that she has undergone four surgeries in the past ten months, and her recovery has been a busy and emotional journey. “So many days spent in bed I can’t even count and have learned more about cancer, cancer treatment and hormones than I ever could have imagined,” Munn wrote.

“Surprisingly, I’ve only cried twice. I guess I haven’t felt like there was time to cry. My focus narrowed and I tabled any emotions that I felt would interfere with my ability to stay clearheaded.”

Munn thanked the medical professionals who treated her, friends who have had breast cancer who offered support and advice, and thanked her partner, the comedian John Mulaney, for “the nights he spent researching what every operation and medication meant and what side effects and recovery I could expect,” for being by her side during the operations and for always placing a photo of their son Malcolm next to her, “so it would be the first thing I saw when I opened my eyes.”

“Thank you for fighting so hard to be here for us. Malc and I adore you,” Mulaney replied in the comments.

After a difficult year-long health battle, Munn was back on her feet and was seen at the Academy Awards on Sunday, alongside John Mulaney.

Breast cancer is a heartbreaking thing for anyone to go throug