What is breast cancer? must read

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What is breast cancer?

The breast is a gland that consists of breast tissue supported by connective tissue (flesh) surrounded by fat.

The easiest way to understand how the inside of the breast is formed is by comparing it to an upturned bush. Its leaves are known as lobules and they produce milk that drains into ducts that are the branches of the breast tree. These in turn drain into 12 or 15 major or large ducts which empty onto the surface of the nipple, just like the branches of a tree drain to the trunk.

Breast cancer develops from the cells that line the breast, lobules and the draining ducts.

Cancer cells that remain confined to the lobule and the ducts are called 'in situ' or 'non-invasive'. They are sometimes also referred to as pre-cancers in recognition of the fact that these cells have not yet gained the ability to spread to other parts of the body, which is the feature that most people associate with cancer.

An invasive cancer is one where the cells have moved outside the ducts and lobules into the surrounding breast tissue.

How common is breast cancer?

Breast cancer is the most prevalent cancer among women and affects approximately one million women worldwide.

Breast cancer accounts for 30 per cent of all female cancers in the UK and approximately 1 in 9 women in the UK will get breast cancer sometime during their life.

What are the risk factors leading to the development of breast cancer?


Age

The incidence of breast cancer increases with age and doubles every 10 years until the menopause when the rate of increase slows.

Approximately a quarter of breast cancers affect women under the age of 50, a half occur between the ages of 50 and 69 and the remaining quarter develop in women who are 70 years or older.


Geographical variation

There is quite a difference in incidence and death rate of breast cancer between different countries. The biggest difference is between Eastern and Western countries.

Recent, age-adjusted figures show that the rate of breast cancer per 100,000 women is 24.3 in Japan and 26.5 in China compared to 68.8 in England and Wales and 72.7 in Scotland and 90.7 in North America in white females.

However, studies of women from Japan who emigrate to the US show that their rates of breast cancer rise to become similar to US rates within just one or two generations, indicating that factors relating to everyday activities are more important than inherited factors in breast cancer.


Reproductive factors

Women who start menstruating early in life or who have a late menopause have an increased risk of breast cancer. Women who have natural menopause after the age of 55 are twice as likely to develop breast cancer as women who experience the menopause before the age of 45.


Age at first pregnancy

Having no children and being older at the time of the first birth both increase the lifetime incidence of breast cancer. The risk of breast cancer in women who have their first child after the age of 30 is about twice that of women having their first child before the age of 20.

The highest risk group are those who have their first child after the age of 35 and these women have an even higher risk than women who have no children. These observations indicate a ‘menstrual cycle effect’. During the monthly cycle a woman’s fluctuating hormone levels cause several changes within breast tissue, which are repeated every month.

These changes possibly encourage or amplify abnormalities in the cell repair processes within breast tissue, which can in some cases lead to breast cancer later in life.

Women who have fewer menstrual cycles before their first pregnancy, either through being older when they start menstruating or younger when they first get pregnant, run less chance of such an abnormality occurring.


Inherited risk

Up to 10 per cent of breast cancer in Western countries is due to an inherited factor. This factor can be passed on from either parent and some family members pass on the abnormal gene without developing cancer themselves.

It is not yet known how many breast cancer genes there are, but to date, two specific breast cancer genes have been identified (BRCA1 and BRCA2).


Previous breast disease

Women with certain benign changes in their breasts are at increased risk of breast cancer. These women present with a breast lump, have an operation and the breast tissue removed shows severe overgrowth of the cells lining the breast lobule.

The technical name for this type of breast condition is ‘severe atypical epithelial hyperplasia’. Although benign in itself, its occurrence in a particular woman multiplies her risk of developing breast cancer during her life by a factor of four.


Radiation

Doubling of the risk of breast cancer was observed among teenage girls exposed to radiation during the second world war.

Another study of women who received radiation to the chest as a result of repeated X-rays for tuberculosis, found that there was a risk among women who were first X-rayed between the ages of 10 and 14 years. Fortunately, as TB itself has been prevented, this risk is less relevant today.

Other studies have shown that women with Hodgkin's disease who received radiation therapy to the chest have an excess risk of breast cancer. As they are surviving to older age they are now developing not only unilateral but bilateral breast cancer.

The increase in risk depends on the dose and the age at which they received radiation. Data has also suggested that there is increased risk of breast cancer in the other breast in patients having radiation to one breast.


Lifestyle

Although there is a close correlation between the incidence of breast cancer in a country and the dietary fat intake of that country, more detailed studies have shown that there does not appear to be a particularly strong or consistent relationship between fat intake in any individual and their risk of developing breast cancer.


Weight

Being overweight is associated with a doubling of the risk of breast cancer in postmenopausal women whereas amongst premenopausal women obesity is associated with reduced breast cancer incidence.


Alcohol intake

Some studies have shown a link between the amount of alcohol people drink and the incidence of breast cancer, but this relationship is not consistent and may be influenced by dietary factors other than alcohol.


Hormones

Women who take the contraceptive pill are at a slight increased risk while they take the Pill and they remain at risk for 10 years after coming of the Pill.

The increased risk is, however, very small and cancers diagnosed in women taking the oral contraceptive Pill are less likely to have spread than those cancers diagnosed in women who have never used the oral contraceptive.

The duration of use, age at first use, dose and type of hormone within the contraceptive appears to have no significant effect on breast cancer risk.

Women who begin taking the Pill before the age of 20 appear to have a higher risk than women who begin taking oral contraceptives at an older age.


Hormone replacement therapy

Among current users of hormone replacement therapy (HRT) and those who have stopped using it one to four years previously, there is an increased risk of breast cancer.

The risk increases 1.023 times for each year of HRT use. This increased risk is very similar to the effect of a delay in the menopause by one year. The risk of breast cancer in a woman who has not used HRT increases 1.028 times for each year she is older at the menopause.

HRT using a combination of oestrogen and progestogen has been shown to be associated with a slightly higher risk of breast cancer than oestrogen-only HRT.

Cancers diagnosed in women taking HRT tend to be less advanced clinically than those diagnosed in women who have not used HRT. Current evidence suggests that HRT does not increase breast cancer mortality.


What are the symptoms of breast cancer?


Generally, breast cancers are not painful and women do not feel unwell with them.


Breast cancer is now commonly diagnosed by breast screening in women who have no symptoms. Approximately 6 in every 1000 women between the ages of 50 and 64 who attend for screening will be found to have breast cancer the first time they attend screening.


A lump in the breast. In many cases, the woman herself will first suspect the disease because she notices a lump or an area of lumpiness or irregularity in her breast tissue. This may happen when she is examining her breasts or while washing or applying lotion to her breasts, or the lump may be visible.


Other signs of breast cancer include:


a change in the skin: there is often dimpling or indentation of the skin with the formation of wrinkles. The nipple might be pulled in or there may be a discharge from the nipple.


occasionally the nipple itself changes. A rash can affect the nipple or the nipple may weep.


the breast may swell and become red and inflamed or the skin may change and become like the skin of an orange. In some breast cancers this is due to a blockage of the drainage of fluid from the breast.


patients sometimes present with a lump under the arm which is a sign that the cancer has spread to the lymph glands.


How is breast cancer diagnosed?

If a woman has any breast symptoms it is very important that she consult her doctor so that the cause of these symptoms can be found. If breast cancer is found at an early stage this improves the chances of recovery. As a rule, the doctor will ask her a number of questions.


Does the lump vary in relation to her menstrual cycle?


What previous breast problems has she had?


Is there any breast cancer in her family?


How many children has she had?


Physical examination

The doctor will look at her breasts, first with her arms by her sides, then above her head and, finally, with her arms pressing on her hips.

By looking carefully at the outline of the breast in various positions, the doctor can often see changes in the outline of the breast, which will help identify the site and cause of any problems.

Next, her breasts are examined while she is lying flat with her arms folded under her head.

If, during this examination, the doctor finds a lump, he or she will concentrate on this area examining with the fingertips and measuring the lump.

After checking her breasts, the doctor usually carefully examines the lymph glands under the patient's arm pit and those in the lower part of her neck.

Should the patient need any further investigations, the breast specialist in the breast clinic will organise any tests that are necessary.


Mammograms

If the patient is over 35 and has not had a breast X-ray within the past year, the doctor may arrange for one to be performed. Breast X-rays are known as mammograms.

Mammograms are a good way of identifying abnormalities in the breast, but they don't always tell whether they are benign or malignant.

Further tests are sometimes necessary and these tests include ultrasound and fine needle aspiration cytology (FNAC).


Ultrasound scanning

X-rays do not pass easily through the breasts of young women. Ultrasound scanning, which is familiar to many women by its use to look at babies during pregnancy, can also be used in the breast to tell whether a lump is fluid or solid.

Ultrasound is not useful as a screening test. It is useful if an abnormal shadow is seen on the mammogram because ultrasound is an accurate way of judging whether any abnormality is benign and straightforward or whether it is more likely to be serious.


Needle tests (FNAC)

Inserting a needle into the lump will show whether it is full of fluid (a cyst) or solid. The needle can allow a sample of cells to be removed for examination under the microscope (a process called cytology) and this is a very accurate method of finding out whether the lump is benign or malignant.

If there is an abnormality on the mammogram, but no lump to feel, then using either the X-ray machine or the ultrasound machine, it is possible to guide the needle into the area of abnormality and to obtain enough cells or tissue to obtain a definite diagnosis. The very fine needles used for this procedure give rise to its name.


Having the lump removed

After investigation, the doctor may decide the lump is benign and that it can be left alone. Alternatively the doctor may suggest that the lump should be removed. This is called an excision biopsy and it can be performed either while the patient is awake under local anaesthesia or, more commonly, under a general anaesthetic.

Before any operation, the patient will be asked to sign a consent form agreeing to the removal of the lump. It is important for the patient to know that the doctor performing the operation will only remove the lump and will not take any more tissue away without explaining any further procedure to the patient first and being given her consent.


What are the types of breast cancer?

Breast cancer was originally described according to its appearances, so words like scirrhous (meaning woody) were used and still appear in the literature.

More recently, breast cancer has been classified according to its appearances when under the microscope.

Early pathologists classified breast cancers into 'invasive ductal' cancers and 'invasive lobular' cancers believing that invasive ductal cancers arose in ducts and invasive lobular cancers in the lobules. However, it is now clear that all invasive ductal and invasive lobular cancers arise either in the terminal duct or the lobule. As the terms invasive ductal and lobular are in such common usage and as they have different appearances under the microscope they are still used.

A more logical classification divides tumours into those of 'special' and 'no special' type. Invasive carcinoma of no special type is also commonly referred to as invasive ductal carcinoma. It is the most common type and accounts for up to 85 per cent of all breast cancers.

Special types of tumour have particular microscopic features and these include invasive lobular carcinoma, invasive tubular, cribriform, medullary and mucinous cancers, with other types being uncommon. Many of the special type cancers have a better prognosis - in other words the patient has a higher chance of survival.

When a cancer is examined under the microscope, it is usually possible to assess how aggressive it is: in other words how far and how fast it is likely to spread. The tumour may be assigned to one of three grades ranging from grade I to grade III in order of seriousness. For instance, a grade I cancer is non-aggressive and unlikely to cause harm. In contrast, grade III tumours are aggressive and likely to cause harm, but can sometimes be controlled with effective treatment.

How is breast cancer treated?

The treatment of the disease depends on the tumour type and the stage of disease - how far it has spread to involve either lymph glands or other organs in the body. There are various ways a cancer can be staged and classified.

A simple way of staging or classifying breast cancer is to divide it into three groups.


Early or operable breast cancer

This describes cancer that is confined to the breast and/or the lymph glands in the axilla (arm pit) on the same side of the body


Locally advanced breast cancer

This has not apparently spread beyond the breast and axillary lymph glands but involves the skin or the chest wall of the breast.

These cancers tend to have a worse outlook than early breast cancer and are usually best initially treated by drug therapy or radiotherapy rather than surgery. In locally advanced breast cancer the skin of the breast can either be directly involved by cancer or it is swollen or red. These changes occur because cancer cells get into the fluid channels that drain the breast (lymphatics) and block them, which causes the skin of the breast to be swollen and look like the skin of an orange (peau d'orange).

Locally advanced breast cancers were initially treated with surgery but this treatment was successful in only about 30 per cent of patients.

In the remainder, the cancer recurred in the areas immediately next to where the surgery was performed


Advanced breast cancer

This is where the cancer has spread beyond the breast and arm pit to other parts or organs of the body such as lymph glands in the neck, bone, lungs, liver and brain.


Other tumours in the breast

A rare form of tumour in the breast arises from the supporting tissue and is called a sarcoma. These types of tumour are rare and account for much less than 1 per cent of all malignant tumours within the breast. These are usually best treated by surgery.

How does breast cancer develop?

Initially, carcinoma cells are confined within the lobule and adjacent ducts. These are known as non-invasive cancers or 'carcinoma in situ'.

As with invasive disease, there are two main types - ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS).

Under the microscope these look different and, clinically, these two types of non-invasive cancer behave differently and require different treatments. Certain types of DCIS develop characteristic tiny particles of calcium within them. These particles show up as tiny white dots on a mammogram.

DCIS is much more common than LCIS. DCIS accounts for over one fifth of all types of cancer detected by breast screening.

DCIS is treated by surgery which may be followed by radiotherapy and hormonal treatment. LCIS when diagnosed is usually treated by simple follow up with regular mammograms or with hormonal tablets (tamoxifen).

Only rarely is surgery used for LCIS.

DCIS is considered to be a pre-malignant breast disease. It is not early breast cancer, but if left untreated DCIS cells eventually spread into the surrounding connective tissue of the breast to form an invasive cancer. The time period in which DCIS changes into an invasive cancer appears to be over months and years rather than days or weeks.

When an invasive cancer has developed, it is at this stage that there is a risk that cancer cells can spread to nearby lymph glands, the most common lymph glands affected being in the axillary (armpit) region.

Cancer cells can also enter the blood stream through the blood vessels that supply the cancer and then move to other organs of the body where they grow and cause problems in these organs. The most common sites for breast cancer to spread to are the bones, lungs, liver and brain. Sarcomas if they spread do so mainly through the bloodstream.

Can breast cancer be prevented?

One particular medicine used to treat breast cancer, tamoxifen (eg Nolvadex D), has been shown in an American study to reduce the risk of developing breast cancer by approximately 50 per cent in women at high risk of developing the disease. Research with tamoxifen and some other breast cancer medicines is still being carried out to determine if these are suitable options for preventing breast cancer. However, tamoxifen is associated with some rare but serious side effects that may make it unsuitable as a preventive measure.

Screening, as currently practised can reduce the mortality but not the incidence of breast cancer (and then only in the age group that is screened).

Once a woman reaches the age of 50, she will be invited to take part in a breast screening programme. In the UK, this means having a mammogram every three years up to the age of 64, although the upper age limit of routine screening is currently being extended to 70 years throughout the UK.. The aim of screening by mammography is to pick up cancer while it is still small before it has a chance to spread.

There are various reasons why women are not normally screened below the age of 50:


breast cancer is less common in younger women.


mammography is less likely to detect breast cancer in young women because the breast tissue is denser which can make breast cancer much more difficult to detect.


there is no evidence that breast screening below the age of 50 is cost effective.