The team used advanced imagining techniques to analyse breast tissue from more than 500 women aged 15 to 86 years old. The tissue included biopsies taken from women for non-cancer-related reasons.

Combining these images with details of the hormone receptors and immune cells present, as well as the tissue architecture, the researchers were able to map how breast tissue changes over time in unprecedented detail. Their findings point to reasons why breast cancer risk increases with age and why tumors in younger women differ biologically.

The author added: “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 map revealed that all types of cells become fewer in number and divide far less often. Milk-producing structures known as lobules shrink or disappear, while the ducts that that carry milk become relatively more common, with the supporting layer around them becoming thicker. Fat cells increase while blood vessels decrease.

Meanwhile, changes occur in the immune environment. Younger breasts have more B cells and active T cells, which helps them identify and kill cancer cells. As tissue ages, these types of cells decline in number, replaced by other types of immune cell that indicate a more inflammatory and potentially less protective immune environment. ScienceMission sciencenewshighlights.

Scientists have created the most detailed map to date, comprised of over 3 million cells, showing how breast tissue changes as women age – including dramatic changes during menopause.

The map reveals how, as women age, the number of cells in their breast tissue decreases, and these in turn proliferate less, and the structure of breast tissue changes. This creates a ‘micro-environment’ in which cancer cells can thrive.

Details of the study are published in Nature Aging.