Breast cancer diagnoses in women under 50 have increased significantly in the past two decades, primarily driven by estrogen-receptor positive tumors. This research highlights the importance of early detection and the need for prevention strategies. Prevention efforts in young women need to adopt a targeted approach to address racial disparities in incidence rates observed at different age phases.
https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2814306 (open access)
I do recall reading somewhere that women throughout the industrialized world have seen their breast size increase substantially since the mid-20th Century. Sadly, risks of cancer increase along with this