Olivia Munn Diagnosed With Luminal B Breast Cancer: What to Know About the Aggressive Disease

The actress revealed her battle with breast cancer on Tuesday.

Olivia Munn revealed on Tuesday that she privately battled breast cancer and that she underwent a double mastectomy to combat the aggressive form of cancer doctors discovered.

In a series of posts shared to social media, the actress, 43, was candid about her diagnosis, which she received in 2023. Munn said she "took a genetic test that checks you for 90 different cancer genes... I tested negative for all, including BRCA (the most well-known breast cancer gene)."

Munn explained that the following winter, she also had "a normal mammogram." Then, two months after that, she was diagnosed with an "aggressive, fast moving cancer," categorized as Luminol B.

Munn's efforts to raise awareness about breast cancer have seemed to spur on many to want to learn more about the cancer she has been fighting and how breast cancers are studied and categorized to doctors, in an effort to better treat them.

According to the Mayo Clinic, there are four main groups that breast cancers are divided into based on recently developed genetic tests of the cancer cells themselves.

The groups are based on whether or not the cancer cells have receptors that use naturally occurring hormones -- estrogen and progesterone -- to promote their growth and development. Cancers that grow through estrogen are ER positive, while cancers with receptors for progesterone are PR positive.

Cancers without hormone receptors at all are known as HR negative.

Additionally, doctors have been able to examine cancer cells for the HER2 gene, and cancers with too many copies of the HER2 gene, produce too much of the growth-promoting protein HER2.

The cancer groups are made up of different types of cancer with different group markers and makeups. The first group, known as Luminal A, include "tumors that are ER positive and PR positive, but negative for HER2." These types of breast cancers "are likely to benefit from hormone therapy and may also benefit from chemotherapy."

The second group, known as Luminal B -- the type that Munn has been battling -- include "tumors that are ER positive, PR negative and HER2 positive." These are cancers that are "likely to benefit from chemotherapy and may benefit from hormone therapy and treatment targeted to HER2."

The third group, known as HER2-Positive, are cancers that are HER2-positive but PR and ER negative. These types of cancer are "likely to benefit from chemotherapy and treatment targeted to HER2."

The fourth group, known as basal-like cancers or triple-negative breast cancer, include "tumors that are ER negative, PR negative and HER2 negative." Chemotherapy specifically is considered to be the most effective treatment in these cases.

"Understanding more about the chemical and genetic makeup of your cancer may help doctors choose the most effective treatment for your specific cancer," the Mayo Clinic stresses.

Olivia Munn and husband John Mulaney attended this year's Oscars just days before the actress shared her story. - Frazer Harrison/Getty Images

In Munn's post, she revealed that in the past 10 months, she has undergone a total of four surgeries, and has learned a lot about the disease and hormones. 

"Surprisingly, I've only cried twice," she wrote. "I guess I haven't felt like there was time to cry. My focused narrowed and I tabled any emotions that I felt would interfere with my ability to stay clearheaded."

Munn admitted that she only allowed people to see her when she had "energy," noting she took many trips to the park with her and husband John Mulaney's 2-year-old son, Malcolm.

"I've kept the diagnosis and the worry and the recovery and the pain medicine and the paper gowns private," she said. "I needed to catch my breath and get through some of the hardest parts before sharing." 

Munn also revealed that it may have been another year before her cancer was detected if it wasn't for her doctor doing an assessment of her breast cancer risk. After a biopsy, Munn shared that she had the mastectomy. 

"Thirty days after that biopsy I had a double mastectomy," she wrote. "I went from feeling completely fine one day, to waking up in a hospital bed after a 10-hour surgery the next." 

Munn ended her message with thanks. In one special note, she celebrated Mulaney for stepping up and taking care of their young son.

Munn's emotional post ended with a photo of her hospital bedside table, which had a framed picture of Mulaney and their smiling baby boy. 

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