Breast Cancer Explained

---

The whole body is composed of trillions of microscopic units known as cells. We have many different types of cells ranging from muscle cells to skin cells, each adapted for its function. We are continually losing cells and making cells to replace them. It is important that the process of losing cells is balanced with the process of making cells to ensure our body stays healthy.

Although we have many different types of cells, they all have the same DNA. Human DNA has about 20,000 small segments, which are known as 'genes'. These genes are like instructional codes which tells the cells what to do, ranging from how much sugar the cell must store to how the cell can divide to make new cells. Healthy DNA is important in our cells to ensure our cells behave normally. 

However, if the DNA is not healthy, then the cells can behave abnormally. This can happen if the instructional code of a gene is changed in some drastic way, which is known as a 'mutation'. If you get a mutation in a gene that codes the instructions for making new cells, then this cell may start making a lot of new cells without limitation. This forms a clump of cells known as a 'tumour'. 

The tumour itself may be harmless, also known as 'benign'. However, if the cell has more mutations in specific places in the DNA code, then it may instruct the tumour cells to try and spread to the rest of the body. If the tumour cell has the potential to spread to the rest of the body, then this is known as cancer, also known as a 'malignancy' or 'neoplasm'.

Usually the body's own natural immune system is very good at recognising cancer cells and destroying them, just like it destroys bad bacteria. However, very rarely a cancer cell may avoid being detected by the immune system, and the cancer will grow, and potentially spread to the rest of the body. 

This spreading, known as 'metastasis', is what makes cancer so deadly. It commonly spreads to the lungs, brain and liver where the cancerous cells can continuously grow in number. It can quickly grow very big, at which point it starts to kill the normal cells in the lungs, brain or liver, and ultimately lead to death.

The aim of treatment is to kill and remove the cancerous cells before they spread to the rest of the body. This is why early diagnosis is absolutely crucial.

As mentioned in the previous section, cancer is caused by mutations (changes in the DNA code). Most mutations are minor and harmless and cause no noticeable change in the cell's behaviour. However, some mutations cause major changes to the cell's behaviour, which can lead to cancer. There 2 ways in which cancer-causing mutations can occur:

• You can be born with the mutation, it may be passed down from your parents genes (these genes might be 'hidden' in the parents, so they might not get cancer)
• You can acquire the mutation over your lifetime. As you get older, the number of mutations accumulate, so the risk of cancer goes up. The chances of a mutation go up if you were exposed to hazards such as high radiation

Based on extensive research, we know that there are range of different 'risk factors' which increase the likelihood of a woman getting breast cancer in their lifetime. The risk factors are:

• Age (most common between the ages 50-70)
• Family history of Breast cancer, Ovarian cancer, or Prostate cancer (you may have inherited the same mutated gene, known as BRCA1 and BRCA2)
• Having an early first period or late menopause
• Having no children or not breastfeeding your children
• Prior therapy with oestrogen-progesterone Hormone Replacement Therapy (HRT) (modern day HRT with just oestrogen has lower risk)
• Unhealthy lifestyle including smoking, regular alcohol intake and being overweight

• Any new lumps in breast or armpit
• Any change in breast size, shape or feel 
• Changes in nipple, such as inversion, rashes and discharge
• Changes in breast skin, such as dimpling or puckering
• It may have no symptoms (especially if the cancer is in the early stages, and is detected through the screening programme)

Regular self-examination should help you learn what is normal, and help you detect when something is not quite right. You are recommended to get an appointment with your GP as soon as possible if you notice worrying changes.

If a patient has worrying signs and symptoms of breast cancer, they will be referred for comprehensive diagnostic tests known as 'triple assessment' within a fortnight. Additionally, around 4 out every 100 breast cancer screenings have 'abnormal' results, and these patents are also offered triple assessment as detailed below:

1. Clinical assessment: This is a physical examination of the breast to look for any suspicious signs of cancer
2. Imaging assessment: This is usually an x-ray of the breast (mammography), and there may also be ultrasound assessment.
3. Biopsy: If any lump was found from clinical and imaging assessment, then it is investigated further by using a needles to obtain a small sample of the lump, and this is then analysed under the microscope.

There are 2 types of staging: Stages 0-4 or TNM staging. They both describe how much the cancer has grown and spread.

One of the ways cancer spreads is through the lymphatic system, which are like the body's water drain. The lymphatic capillaries remove excess water. Lots of lymphatic capillaries connect to small structures called lymph nodes. Then the lymph node sends the extra water back to the heart so it can re-enter the blood. The lymphatic capillaries also provides a path for small cancer cells to enter the lymph nodes, and then the blood to spread to the rest of the body. Therefore, it is important to see if there are any cancer cells in the lymph nodes, to indicate how much the cancer has already spread.

In order to see if the cancer has spread anywhere else in the body, a CT scan of your chest, tummy and sometimes the head may be done. This is because if the cancer cells do spread, they commonly go to the lungs, bones (especially spine), brain and liver.

Staging systems

Stages 0-4:

• Stage 0: This isn't 'true' cancer. Slightly abnormal cells have been found which may or may not develop into cancer. Known as Ductal Carcinoma in situ (DCIS).
• Stage 1: The tumour is less than 2cm big, and it hasn't spread to rest of the body (although there may be tiny microscopic invasion of cancer cells to nearby lymph nodes)
• Stage 2: The tumour is 2-5cm big, and it has spread to some lymph nodes in armpit, but not spread to rest of body
• Stage 3: The tumour is over 5 cm, it may have grown into the breast skin or muscle behind the breast, it has spread to many lymph nodes in the armpit
• Stage 4: The cancer has spread to a different organ (metastasis)

Note that this has been simplified and substages such as 3a, 3b and 3c exist. More detailed information can be found here.

TNM staging:

• T (1,2,3,4): The number after T indicates how large the tumour is
• N (0,1,2): The number after N indicates the extent the cancer has spread through to the lymph nodes
• M (0,1):  The number after M indicates if the cancer has spread to a different organ (metastasis) or not

This is they staging system doctors tend to use as it is a more accurate descriptor of how developed the cancer is.

Grading system

As well as staging, it is important to 'grade' the cancer cells. This describes how abnormal the cancer cells are under the microscope, in comparison to normal cells. This gives an indication of how quickly the cells are growing

• Low (G1): Cancer cells look abnormal, and have slow growth rate
• Medium (G2):  Cancer cells look quite abnormal, have intermediate growth rate
• High (G3): Cancer cells look very abnormal, have high growth rate

Hormone Receptor Status

Finally, one of the reasons cancer cells overgrow is due to hormones. Therefore, a treatment strategy may be to stop the cells from responding to these hormones. So it is important to see which hormones are influencing the cancer cells.

• ER (positive or negative): If positive, this indicates that the cancer cells are growing in response oestrogen
• PR (positive or negative): If positive, this indicates the cancer cells are growing in response to progesterone 
• HER2 (positive or negative): If positive, this indicates the cancer cells are growing in response to HER2