Australasian Science: Australia's authority on science since 1938

The Breast Exposed

mammogram

Why does the breast so commonly get cancer when it is not a tissue that is particularly exposed to the environmental agents that increase cancer risk in other major organs?

By Wendy Ingman

Why is the breast so prone to cancer?

The full text of this article can be purchased from Informit.

The skin and lungs are two tissues that are frequently bombarded with cancer-initiating factors, such as ultraviolet rays from the sun and smoke and pollutants in the air we breathe. Yet breast cancer is the most common type of cancer in Australian women, affecting one in eight before the age of 85. It is more common than skin melanoma and lung cancer.

Why, then, does the breast so commonly get cancer when it is not a tissue that is particularly exposed to the environmental agents that increase cancer risk in other major organs? Is there something unique about this tissue that makes it particularly susceptible?

The breast undergoes cellular changes over the course of the monthly menstrual cycle, and and these changes affect cancer susceptibility. Rising levels of the hormones oestrogen and progesterone occur immediately after the egg is released from the ovary, and these hormones cause the breast cells to divide and change to accommodate further development if pregnancy occurs.

If the woman becomes pregnant, the cells in the breast continue to develop and become the milk-producing structures required to feed a newborn baby. But if pregnancy does not occur there is a drop in progesterone, which triggers the death of the newly developed breast cells. This occurs at the same time women have their period.

Then the cycle starts again, and continues...

The full text of this article can be purchased from Informit.