(NewsNation) — Breast cancer rates are rapidly increasing among younger women, a new study released by the American Cancer Society found.

Despite the overall breast cancer mortality rates declining 44% since 1989, women in their 20s, 30s and 40s have seen a 1.4% increase in breast cancer diagnosis. Doctors haven’t been able to understand what has been driving the growth in cases.

Breast cancer remains the second most common cancer for women in the U.S. just behind skin cancer, which is the most common cancer in the U.S., according to the ACS. About one in eight women is diagnosed with invasive breast cancer in their lifetime, the report said.

Britta Knight, a breast cancer survivor, was diagnosed at 33. She, like many young women diagnosed with the illness at a young age, was caught by surprise as her life was turned upside down by an illness she wasn’t expecting — at least in her 30s.

“It was so fast-moving,” Knight said. “When I saw the oncologist that morning, she was just like, you’ve got breast cancer. We’re going to do a PET scan tomorrow. We’re going to put a port in on Friday.”

Knight was treated nearly immediately. She found herself on chemo for months, and out of work for at least six months.

And while Knight’s story has become all too common for young women, she is one of the luckier ones because she survived.

Nationally, about 350,000 women are expected to get a breast cancer diagnosis in 2024 and an estimated 42,250 will die, according to the ACS.

Most notably, the report shows breast cancer rates among Asian American and Pacific Islander women under the age of 50 have surged by 50% since 2000. Black women, while less likely to be diagnosed with breast cancer than white women, face a 38% higher mortality rate.

Health providers said getting mammograms and ultrasounds as early as 40 is vital to women’s health.

“Breast cancer in younger women is a whole different genetic entity. It is more aggressive, and because it is more aggressive, it is important that we look earlier and that we really either do hereditary testing and familial testing for Braco genes in families that are high risk,” American Cancer Society spokesperson and oncologist Dr. Estelamri Rodriquez said.

Physicians say there is no clear data or reason why we are seeing this rise in breast cancer cases in younger generations. Delayed diagnoses due to missed screenings, genetic history, a sedentary lifestyle, alcohol, environmental factors and toxins in our foods are all possible reasons for the increase in breast cancer numbers for younger women.