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What is breast cancer?

What is cancer 

Normally cells in our bodies grow and divide in a controlled way, but sometimes this process gets out of control. Cancer is the name for a group of diseases that develop when the body’s cells grow in an uncontrolled way and spread into the body’s tissues. 

When cancer spreads into the body’s tissues, it is called invasive cancer. The site where cancer starts is called the primary cancer. Cancer that starts in the breast is called breast cancer. It can develop at any age. 

What a breast looks like on the inside 

Breasts are made up of small sacs and tubes called ‘lobules’ and ‘ducts’, surrounded by other tissues. The lobules produce breast milk and the ducts carry the milk to the nipple (see Figure 1 below). 

All women and men have breast tissue, although the ducts and lobules essentially have no function in men. 

Breast cancer 

Breast cancer is the abnormal growth of cells lining the breast ducts and lobules (see Figure 1). The cells grow uncontrollably and over time, can spread into surrounding breast tissue. This is called ‘invasive breast cancer’. It has the potential to spread to other parts of the body. 

While breast cancer is most common in women, it also affects a small number of men each year. 

Figure 1: View of the female breast from the inside 

Types of breast cancer 

Breast cancer - types and subtypes 

Breast cancer is not one disease. There are different types and subtypes of disease that are referred to as breast cancer. Therefore the treatment you receive for your breast cancer may be quite different from the treatment other people you meet have. Click here to read more.  

More Information 

BCNA’s My Journey 

My Journey is where you go to get all your breast cancer information about your diagnosis in one place. Whether you have early breast cancer, DCIS or metastatic breast cancer, My Journey provides you with the latest information tailored to suit your situation. You can access this information through My Journey via an app or web browser at