Peloton instructor Leanne Hainsby, 35, said she was diagnosed with breast cancer after a doctor told her not to worry about a lump in her breast

• Peloton instructor Leanne Hainsby said she was diagnosed with breast cancer at age 35.
• She wrote on Instagram that she noticed a lump in her breast, but a doctor initially said not to worry.

Peloton instructor Leanne Hainsby, 35, said that she has been privately battling breast cancer for the past six months while continuing to lead classes.

"Where possible, I have continued to show up as 'normal,' but my reality most of the time, has looked very different," she wrote on Instagram. "My classes have given me a focus and some sparkle in an incredibly tough time, so thank you to the members who had no idea the amount of joy they were bringing to me every day."

The British cycle instructor said that she was diagnosed in August 2022 after multiple scans and appointments, during which she was "completely terrified."

She said she subsequently completed 12 weeks of chemotherapy, going to weekly treatment after teaching her Wednesday morning live classes.

"Chemo is no joke," Hainsby wrote.

She also noted she had undergone surgery, and expects to continue treatments and hospital visits, although she recently received "very good news."

Hainsby wrote that she was sharing her story now to raise awareness — she said she initially sought a doctor's advice after finding a lump in her breast, and was told not to worry.

"I trusted my gut and got a second opinion. That saved my life," Hainsby said.

About 9% of new breast cancer cases in the US occur in women under 45, and the disease is most common in women over 50, according to the Centers for Disease Control and Prevention.

Family history of breast cancer is a major risk factor, but other factors like reproductive health and alcohol use can also play a role, according to the Mayo Clinic.

The most common symptom is a lump in the breast area, and regular self-screenings and medical exams can help reduce the risk. Other symptoms of breast cancer include skin irritation, pain, or any other changes in the area that seem unusual, a breast surgeon previously told Insider.