What is Breast Cancer?

Breast cancer (also known as carcinoma of the breast, or malignant breast tumour/ neoplasm) is cancerthat develops from tissue of the breast. In the majority of cases the cancer originates either from:

  • The epithelium (i.e. the inner lining of the milk ducts); or from
  • The breast lobules which produce and supply the breast ducts with milk.

Cancers originating from breast ducts are known as ductal breast carcinomas, while those tumours originating from breast lobules are known as lobular breast carcinomas.

Breast cancer is the most common cancer in the Western developed world, including USA and the UK. More than 50,000 women get breast cancer in the UK every year. In the USA, there are about 230,000 women and 2,200 men affected by breast cancer every year. Most women (~80%) are over the age of 50 years old. However, younger women, and in rare cases (less than 1% of all cases), men, can also get breast cancer.

Currently, in the USA, about 40,000 women and 400 men die from the disease every year. Worldwide, breast cancer accounts for about 23% of all cancer cases in women. Breast cancer currently causes about 450,000 deaths worldwide, which is equivalent  to approximately 14% of all cancer deaths in women). Breast cancer is about 100 times more common in women than in men, although men tend to have poorer prognosis and outcomes, mainly due to delays in diagnosis. 

Histogram showing the incidence and mortality rates of breast cancer around the world.

Prognosis and survival rates of the disease do vary significantly, depending on many characteristics of the tumour (such as size, type and stage), treatment, and geographical location of the patient.  In the Western world, there are high survival rates, mainly due to early diagnosis and effective treatment. As an example, in the UK, more than 80% of women diagnosed with breast cancer, are alive 5 years after being diagnosed with the disease. However, in developing countries, the survival rates are much poorer.

Female breasts are made up of fatty tissue, connective tissue and numerous tiny glands, which are known as lobules. These are responsible for producing milk. When a woman has a baby, the milk is produced in the lobules and is transported to the nipple through small tubes, which are called milk ducts. This enables milk to be available at the nipple for breastfeeding. 

The human body consists of billions of cells, which are extremely small, and can only be seen under the microscope. Under normal conditions, cells grow and multiply in a very orderly way. New body cells are only produced when and where they are required. However, in malignancy (cancer), this highly ordered process gets out of control, and body cells start to grow and multiply uncontrollably.

Women with carcinoma of the breast (breast cancer) may have several symptoms, but the disease usually presents as a breast lump or thickening of the breast (although most breast lumps are not cancerous). If breast cancer is detected at an early stage, it can be fairly successfully treated before it spreads to other parts of the body. 

If a woman notices a new breast lump, or has any other new symptoms, she needs to see her doctor as soon as possible, and have these new changes properly assessed. After a physical examination by your doctor, he/ she may feel it necessary to refer you to a specialist breast cancer consultant (surgeon) or clinic, for further tests, such as a mammogram or ultrasound of the breast.

Types of breast cancer

There are several different types of breast cancer, which may develop in different parts of the breast. Breast cancer is often divided into non-invasive and invasive types.

a) Non-invasive breast cancer

Non-invasive breast cancer is also known as breast cancer (or carcinoma) in situ, or as pre-cancerous cells. This type of breast cancer is found in the ducts of the breast and has not yet developed the ability to spread outside the breast. This form of cancer only rarely presents as a lump in the breast, and is usually detected when a woman has a mammogram. The most common type of non-invasive cancer is ductal carcinoma in situ (DCIS). The other major type of in situ disease, is lobular carcinoma in situ (LCIS).

b) Invasive breast cancer

Invasive breast cancer has acquired the ability to spread outside the breast, although this does not necessarily mean that it has metastasised (spread to lymph nodes or to distant organs such as the lungs or the liver). The most common form of breast cancer is invasive ductal breast carcinoma, which develops in the cells that line the breast ducts. Invasive ductal breast cancer accounts for about 80% of all cases of breast cancer and is sometimes called "no special type".

Schematic diagram showing invasive lobular carcinoma of the breast, with malignant cells breaking through the basement membrane of the lobule.

c) Other types of breast cancer

Other less common types of breast cancer include invasive lobular breast carcinoma, (this develops in the cells that line the milk-producing lobules), inflammatory breast carcinoma, and Paget's disease of the nipple. It is possible for breast cancer to metastasise (spread) to other parts of the human body, usually through either the lymph nodes (small glands which normally filter pathogens, such as bacteria, from the body) or through the bloodstream. If this takes place, it is known as secondary or metastatic breast carcinoma.

Mobile breast screening unit.

2) Breast screening

The exact causes of breast cancer are not fully understood, but there are many different factors which either increase or decrease the risk of developing the disease, including age and family history. Women who undergo through assessment of their breast cancer risk, and are found to have a higher-than-average risk of developing breast cancer (assessed as having moderate or high risk, and not low risk), may be offered extra screening, and in some instances genetic testing for the disease. 

Since the risk of breast cancer rises with increasing age, all women who are between the age of 50 and 70 years old, are invited for breast cancer screening every two to three years. Women over the age of 70, are also entitled to screening, but they need to arrange for an appointment through their doctor or their local screening unit.

3) Treating breast cancer

Breast cancer is usually treated using a combination of surgery, endocrine therapy, chemotherapy, and radiation therapy (radiotherapy). Some women with HER2/neu-positive breast cancer may also be treated using biological treatments (e.g. Herceptin). The daily life of a woman can be affected in many ways, after a diagnosis of breast cancer. However, there is available support for many aspects of living with the disease, including emotional, financial and long-term health issues.

In general, in developed countries, 1 in 9 women are affected by breast cancer sometime during their lifetime. Due to much research in the field, currently there is a fairly good chance of recovery, if breast cancer is detected in its early stages. It is for this reason, that it is extremely important for all women to check their breasts regularly (at least once every month) for any changes, and always get any new changes examined by their doctor.

Treatment of breast cancer is based on the characteristics of the tumour (e.g. size, stage, rate of growth), and hence is individualised for every woman affected by the disease. Treatment may include surgery, drugs (hormonal, (endocrine) therapy and chemotherapy), radiotherapy, and/or immunotherapy. Removal of the cancer by surgery provides the single largest benefit, with surgery alone curing many patients.

In order to further increase the likelihood of cure (i.e. cancer not coming back), several chemotherapy regimens are commonly used in addition to surgery (neo-adjuvant chemo if given before surgery to shrink the tumour, or adjuvant chemotherapy if given after surgery to prevent it coming back). Radiotherapy is usually used after lumpectomy (wide local excision (WLE))/ breast-conserving surgery), and significantly improves local relapse rates, and in many instances, also the overall survival. Some breast cancers are sensitive to hormones such as oestrogen and/or progesterone (ER(+ve) / PR(+ve)), and it  is possible to treat the cancer by blocking these hormones and their effects.