The breast cancer death rate continues to decline among US women, a new American Cancer Society report finds, but diagnoses are becoming more common among younger women.

ACS researchers said nearly 518,000 breast cancer deaths have been prevented with mortality rates dropping by 44% since 1989.

However, overall breast cancer incidence rose 1% a year from 2012 to 2021.

Over those nine years, the diagnosis rate increased 1.4% annually among women younger than 50, 2.5% among Asian American women and 2.7% among Pacific Islander women.

“The encouraging news is breast cancer mortality rates continue to decrease thanks to advances in early detection and treatment,” said Angela Giaquinto, lead study author and ACS associate scientist within the surveillance research team.

“But future progress may be thwarted by increasing incidence, especially among younger women, and consequences of the COVID-19 pandemic, such as delayed diagnosis due to interruptions in screening,” Giaquinto added.

The findings were published Tuesday in CA: A Cancer Journal for Clinicians.

It’s unclear exactly why there’s an uptick in younger breast cancer diagnoses.

Dr. Cindy Cen, a breast surgeon at the Northwell Health Cancer Institute at Lake Success, said there are probably several reasons, including an increase in screenings, greater awareness of the importance of self-exams and poor lifestyle choices.

“Diet, exercise, maintaining a healthy weight, alcohol intake all factor into breast cancer risk,” Cen, who was not involved with the new research, told The Post.

“The trend for cancer diagnosis in younger patients is not limited to breast alone — we are seeing younger diagnoses for colon cancer also for example,” she added. “This younger trend is definitely troubling to see and needs further investigation.”

Breast cancer is the most common cancer among US women after skin cancer.

Researchers predict more than 310,000 new cases of invasive breast cancer in US women and 2,790 cases in men will be diagnosed this year.

About 42,250 women and 530 men are expected to die from the disease this year.

Early detection significantly improves the odds of breast cancer survival.

Experts recommend women at average risk of breast cancer get screened annually starting at 40. Those with a family history of breast cancer and additional risk factors should consult their doctor.