New research at Washington University School of Medicine in St. Louis shows that breast cancer rates are increasing among younger women.

According to a news release from Washington University School of Medicine, researchers show diagnoses of breast cancer have increased steadily in women under age 50 over the past two decades. Since 2016, that steep uphill trend line increased by 3.75% per year, which is significant.

Researchers say the intriguing aspect of the data is that the increase in breast cancer incidence is due almost entirely to an increase in tumors that are estrogen-receptor positive.

Researchers say they need to understand what is driving the specific increase in estrogen-receptor positive tumors.

While overall trends show increases, some decreases have occurred in specific tumor types and among specific groups of women.

Studying trends like these may offer clues to possible prevention strategies.