The cell is the basic building block of the body, making up all of our tissues and organs. As cells grow old and wear out, new ones replace them. This process is called cell division, as is illustrated in Figure 2.
The balance between dying and growing cells is vital to maintain the normal functioning of our bodies. If the number of growing cells exceeds the number of dying cells, then a lump (or tumour) will develop. If the cells in the tumour divide haphazardly and grow in an aggressive manner, this is called a cancer or malignant tumour.
Malignant cells have the potential of invading adjacent tissues and can spread to other parts of the body some distance away from the main (or primary) tumour. This process of distant spread is called metastasis. It can occur through the blood stream or the lymph vessels.
A breast cancer occurs when the cells of the milk glands or the milk ducts grow and divide in a disorderly manner. This may be detected as a lump in the breast. It can take months or years for a tumour of 1 cm in diameter to grow in the breast. It is estimated that a tumour of this size contains one billion breast cancer cells!
There are two main types of breast cancer: invasive and non-invasive (Table 1).
Type 1 – Invasive Breast Cancer
This cancer is more aggressive and has the ability to spread elsewhere in the body and thus cause death.
Type 2 – Non-invasive Breast Cancer
This type is confined to the ducts or lobules of the milk glands. It is a non-invasive cancer and does not usually spread to other parts of the body. However, it may develop into an invasive type if left untreated. The medical name for non-invasive breast cancer is ductal carcinoma in situ (DCIS) if it occurs in the milk gland ducts (tubes), or lobular carcinoma in situ (LCIS) if it occurs in the gland lobules.
LCIS is not considered as cancer as such. The presence of this abnormality in a breast biopsy means the patient has an increased risk of developing breast cancer. The risk means that about 1 in 3 women with LCIS will develop breast cancer within 30 years of being diagnosed with the original condition.