The stage of a cancer describes its size and whether it has spread beyond its original site. The grade gives an idea of how quickly the cancer may develop. Knowing the extent of the cancer and the grade helps the doctors to decide on the most appropriate treatment.

A commonly used staging system for breast cancer is described below:

Ductal carcinoma in situ (DCIS) is sometimes described as stage 0. DCIS is when the breast cancer cells are completely contained within the breast ducts (the channels in the breast that carry milk to the nipple), and have not spread into the surrounding breast tissue. This may also be referred to as non-invasive or intraductal cancer, as the cancer cells have not yet spread into the surrounding breast tissue and so usually have not spread into any other part of the body. DCIS is almost always completely curable with treatment.

Lobular carcinoma in situ (LCIS) means that cancer cells are found in the lining of the lobules of the breast. LCIS can be present in both breasts. It is also referred to as non-invasive cancer as it has not spread into the surrounding breast tissue.

The following stages of breast cancer are known as invasive breast cancer:

Stage 1 The tumour measures less than 2cm. The lymph glands in the armpit are not affected and there are no signs that the cancer has spread elsewhere in the body.

Stage 2 The tumour measures between 2 and 5cm, or the lymph glands in the armpit are affected, or both. However, there are no signs that the cancer has spread further.

Stage 3 The tumour is larger than 5cm and may be attached to surrounding structures such as the muscle or skin. The lymph glands are usually affected, but there are no signs that the cancer has spread beyond the breast or the lymph glands in the armpit.

Stage 4 The tumour is of any size, but the lymph glands are usually affected and the cancer has spread to other parts of the body. This is secondary or metastatic breast cancer.

Breast cancer that has come back after initial treatment is known as recurrent breast cancer.

This section deals with stages 1-3 breast cancer. We have a separate section that discusses secondary breast cancer (stage 4).

TNM staging system

Another staging system known as the TNM system is commonly used. This can give more precise information about the extent of the cancer.

• T describes the size of the tumour.
• N describes whether the cancer has spread to the lymph nodes.
• M describes whether the cancer has spread to another part of the body, such as the bone, liver or the lungs.

Grading refers to the appearance of the cancer cells under the microscope. The grade gives an idea of how quickly the cancer may develop. There are three grades: grade 1 (low-grade), grade 2 (moderate or intermediate grade) and grade 3 (high-grade).

Low-grade means that the cancer cells look very like the normal cells of the breast. They are usually slow growing and are less likely to spread.

In high-grade tumours the cells look very abnormal. They are likely to grow more quickly and are more likely to spread.

Receptors

Some breast cancer cells have parts called receptors, which allow particular types of hormones or proteins to attach to the cell. A sample of the breast tissue will usually be tested for the presence of these receptors. Whether receptors are present or not will affect the type of treatment that you will need.

Some cancers have receptors for the hormones oestrogen and progesterone. If a breast cancer has more than a certain number of oestrogen receptors it is known as being oestrogen-receptor positive (ER+).

Some cancers have receptors for a protein known as HER2.

Your doctors can tell you whether your cancer cells have these receptors.