Breast Cancer Growth Rates

Breast cancer is the growth of abnormal cells in breast tissue. These abnormal cells not only grow at an increased rate compared to normal cells but may also spread, invading other body tissues.

Like a lot of cancers, breast cancer grows by simple cell division. It begins as one malignant cell, which then divides and becomes 2 bad cells, which divide again and become 4 bad cells, and so on. By the time you can feel it, a breast tumour is usually a little more than ½ inch in size – about a third the size of a golf ball. It has also been in your body long enough to have had a chance to spread.

Breast cancer doubles 30 times before it can be discovered. The average doubling time is 100 days, so it can take 8 years of growth until a tumour is visible on a mammogram. Very fast tumours can have a doubling time of 25 days, and very slow breast cancers can have a doubling time of 1000 days. Research shows that tumours may vary their rate of growth over their lifetime.

Depending on breast tissue density and structure, mammography is usually capable of finding breast tumours at approximately 1 cubic centimetre. This is 30 doubling times and about 1 billion cells.

With such a long lead time before becoming clinically evident, there is ample time to put in place effective imaging and health strategies to monitor and reduce risk.