What Is Breast Cancer?

The word cancer refers to a growth of cells in a part of the body that is occurring because the cells have lost control of their behaviour and are growing in an uncontrolled manner. This has usually occurred because the genetic material or DNA within the cells have accumulated a series of errors which has resulted in the cells being able to grow more quickly and without any form of control from the rest of the body. To enable the cells to survive, they have often developed other properties including the ability to spread and push through other tissues, which would normally have contained them, and to stimulate growth of blood vessels so that these abnormal cells can support themselves with nutrition.

When we talk about breast cancer, we are talking about a growth of cancer cells where the starting cell has been one of the cells that would normally make up breast tissue, either in the ducts of the breast tissue or in the glands of the breast tissue.

There are some common terms that are used when discussing cancers that are sometimes interchangeable and produce some confusion.

• Tumour – tumour simply refers to a growth and it is usually used in the setting where there is some form of lump that may be able to be felt or seen on x-rays or other imaging. The word tumour itself does not automatically imply cancer as many tumours can be non-cancerous.
• Malignant – when the word malignant is used to describe a cell’s features in a pathology report, the implication is always that this represents a cancerous process. So in other words, a malignant breast tumour is a breast cancer.
• Benign – a benign tumour is not cancerous. An example of a benign breast tumour is a fibroadenoma, a common tumour or growth often seen in young women.
• Invasive – invasive is used to describe the ability of a tumour to spread beyond the confines of its own growth and into the surrounding tissue. The ability to invade into other tissues or structures of the body is almost always a characteristic of a cancer or malignant tumour.
• Non-invasive or in situ disease  is usually used to describe a population of abnormal or cancer cells that do not show the ability to invade into other tissue or spread elsewhere in the body. This is important because it implies that the abnormal cells or tumour are localized to their site of origin and should be effectively treated or cured by simply removing them.
• Primary – primary cancer refers to the original cancer site and the origin of the cancer. When talking about breast cancer, the cancer that is in the breast is the primary tumour.
• Secondary – secondary refers to cancer that has spread to another site from the primary site. This is also known as a metastasis or metastatic tumor. Secondary tumour sites can be divided into what are called regional or distant sites. If, for example, the lymph nodes under the arm were involved with breast cancer, then these are metastases or secondary tumours that are regional. Cancer that has spread to, for instance, the liver, from a breast cancer is also a secondary or metastatic cancer but this is what is known as a distant metastasis.