Scientists have released on Mar. 31 a detailed map showing how breast tissue changes as women age, which may help explain why the risk of breast cancer increases over time. The study, led by researchers at the Universities of Cambridge and British Columbia, analyzed more than three million cells from over 500 women aged between 15 and 86 years old.
Breast cancer is the most common form of cancer in women and accounts for about 15% of all new cases. Four out of five cases occur in women over the age of 50, with one in seven women developing the disease during their lifetime. Understanding how aging affects breast tissue could provide important insights into prevention and treatment.
The research team used advanced imaging techniques to examine biopsies taken for non-cancer-related reasons. They combined these images with information about hormone receptors, immune cells, and tissue structure to create a comprehensive map that details changes occurring during aging—especially around menopause.
Gupta said: "Our map revealed that as women age, their breast tissue goes through major changes, with the most dramatic changes occurring at menopause. There are changes, too, during their twenties, possibly linked to pregnancy and childbirth, but these are far less pronounced." The study found that all types of cells decrease in number and divide less often as women get older. Milk-producing lobules shrink or disappear while ducts become more common; fat cells increase while blood vessels decrease.
Changes were also observed in immune cell populations within breast tissue. Younger breasts have more B cells and active T cells capable of identifying and killing cancerous cells; however, these decline with age and are replaced by other immune cell types indicating a more inflammatory environment. Co-senior author Dr Raza Ali from the Cancer Research UK Cambridge Institute said: "We don't know for certain why the types of immune cell change. We can speculate that one reason may be because breast milk contains a high concentration of immunoglobulins...and these are produced by B cells." As tissues age further, stromal (scaffold) cells become physically further away from epithelial (milk-producing) cells—potentially making it easier for pre-cancerous mutations to escape detection.
Professor Samuel Aparicio from BC Cancer at University of British Columbia added: "We've previously seen that age dependent changes in estrogen activity occur strongly in milk secreting cells...and now we can see the surprising extent of changes in all cell types including the immune system with age." Dr Ali said: "It isn't surprising that we should see fewer epithelial cells...but the sheer scale of changes across the breast surprised us." He continued: "What is clear from our map is that all these changes create an environment where cancer cells...find it easier with age take hold and spread."
