What causes breast cancer?
The causes of breast cancer are not yet completely understood, but it’s recognised that some factors may increase a woman’s risk of developing it.
There are a number of risk factors including:
- Being overweight
- Having a significant family history of breast cancer. Go to our hereditary fact sheet for more information.
- Taking the contraceptive pill
- Age (eight out of ten breast cancers occur in women over the age of 50)
- Not having children
- Never having breastfed
- Early puberty or late menopause
- Drinking more than two units of alcohol a day over many years
- Certain types of benign breast disease – lobular carcinoma or atypical hyperplasia – are associated with an increased risk of breast cancer.
What are the symptoms?
In most women, breast cancer is first noticed as a painless lump in the breast.
Other, less common signs of breast cancer may include:
- A change in the size or shape of a breast
- Dimpling of the skin of the breast
- A thickening in the breast tissue
- A nipple becoming inverted (turned in)
- A lump or thickening behind the nipple
- A rash (like eczema) affecting the nipple
- A bloodstained discharge from the nipple (this is very rare)
- A swelling or lump in the armpit.
A lump doesn’t always mean cancer though – in fact, most breast lumps are actually benign (non-cancerous) and easily treated.
Common causes of benign breast lumps are:
- Cysts – sacs of fluid that build up in the breast tissue. These are quite common. Nearly 1 in 10 women will have a breast cyst at some time during her life.
- Fibroadenomas – solid tumours made up of fibrous and glandular tissue. These are more common in women in their 20s and 30s.
How is it diagnosed?
Diagnosis starts with a GP, who will complete a breast examination. If he or she isn’t sure what the problem is, or thinks that cancer may be present, a referral will be made to a specialist.
At the hospital, the specialist will ask about general health and any previous medical problems, before completing the examination. He or she will examine the patients breasts again, and feel for any enlarged lymph nodes under arms and at the base of the neck. They will arrange for any tests they think are needed (usually a mammogram or ultrasound scan), followed by a biopsy (tissue sample) to check for cancer cells.
Samples of blood will be taken to check:
- The number of cells in the blood (blood count).
- How well the kidneys and liver are working.
- Whether it contains particular chemicals, which are sometimes produced by breast cancer cells.
The stage of a cancer describes its size and whether it has spread beyond where it started in the body. Doctors use the results of tests and findings from surgery to decide the stage of a woman's breast cancer.
- Stage 1: The tumour measures less than 2cm. The lymph nodes in the armpit are not affected and there aren’t any signs that the cancer has spread elsewhere.
- Stage 2: The tumour measures between 2cm and 5cm, or the lymph nodes in the armpit are affected, or both. 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 nodes 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 lymph nodes are affected and the cancer has spread to other parts of the body. This is called ‘secondary’ or metastatic breast cancer. Breast cancer that has come back after initial treatment is known as recurrent breast cancer.
Grading gives an idea of how quickly the cancer may develop and involves examining the appearance of the cancer cells under a microscope.
- Grade 1 (low-grade) means that the cancer cells look similar to the normal cells of the breast. They are usually slow growing and are less likely to spread.
- Grade 3 (high-grade) tumours have very abnormal looking cells. They are likely to grow more quickly and are more likely to spread.
- Grade 2 (moderate or intermediate grade) cancers fall between the two other grades and have a level of activity somewhere in between.
How is it treated?
Surgery for breast cancer
- Surgery is usually performed to remove the breast cancer. Depending on the extent of the cancer, only the lump will be removed (a lumpectomy) or the whole breast will be removed (a mastectomy).
- Surgery is often followed up with chemotherapy and/or radiotherapy.
For more information on surgery, see our surgery factsheet.
Chemotherapy for breast cancer
- Chemotherapy may be given for breast cancer before surgery (called neo-adjuvant therapy), or after surgery (called adjuvant chemotherapy). The aim of chemotherapy is to systemically destroy any remaining cancer cells.
- If the cancer has spread beyond the breast (metastasised), then further chemotherapy may be used to treat the cancer.
For more information on chemotherapy, check out our chemotherapy factsheet.
Radiotherapy for breast cancer
- After surgery, radiotherapy may be given to any remaining breast tissue, and may be given to the chest wall if the breast has been removed. This is to make sure that any cancer cells that may be left in the area are destroyed.
For more information on radiotherapy, check out our radiotherapy factsheet.
Hormone therapy for breast cancer
- If the cancer cells have receptors for oestrogen and/or progesterone (hormones) on their surface, then hormone therapy may be used to treat the cancer.
For more information, check out our hormone therapy factsheet.
There may also be further treatment with drug called Herceptin®, depending on how likely doctors think it is that the cancer could come back.
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