Normal growth occurs, worn out tissues are replaced and wounds heal. When cells grow out of control and form a mass, the mass is called a tumour. Some tumours grow and enlarge only at the site where they began and these are called benign tumours. Other tumours not only enlarge locally but also have the potential to invade and destroy the normal tissue around them and to spread to distant parts of the body. Each year, more then 17,000 Canadian women will develop breast cancer.
Breast cancer is most common type of cancer in women.
It rarely affects men. Because it tends to occur earlier in life than other cancers and than other major causes of death, such as heart attacks and strokes, it has been shown to be the greatest cause of years of life lost by Canadian women. Clearly it is a major health problem. Cancer of the breast can have all the features which are characteristic of cancers in general. Even a cancer arising from the sacs or ducts may show variation.