Understanding breast cancer

Who hasn’t heard about breast cancer? After all, it’s the most common form of cancer in the UK. But do you know exactly how cells become cancerous and are you aware of the different types and stages of the condition? Read on to find out.

What is breast cancer?

The breast is made up of billions of microscopic cells – in healthy breasts, these cells grow in a controlled way to replace those that have died.

Each cell has a nucleus or a ‘control room’ containing genes whose job is to protect the cell and regulate its growth, maturity, division and death. However, if mutations or abnormal changes occur to the cell’s DNA, some of these genes may be ‘switched off’ while others are ‘switched on’.

In most cells, if the DNA is damaged, the cell either repairs itself or is destroyed by the immune system. But in cancer cells, the DNA is not repaired. The result: the damaged cell is now able to proliferate uncontrollably and ‘produce’ defective cells. Breast cancer is diagnosed when the breast cells’ growth and division get out of control.

Benign or Malignant tumours: Understanding the terms

Unlike a malignant tumour, a benign tumour is less of a health threat and is considered non-cancerous. Benign tumours are only able to grow slowly in a connective tissue capsule (a contained area). What this means is that the cells of the benign tumour cannot invade nearby tissues or spread throughout the body, although they can become very large and compress adjacent tissues. And thanks to the fibrous capsule, benign tumours can be removed surgically.

Malignant tumours are a totally different story – these are classed as cancerous since they grow much faster than benign tumours, and are also able to infiltrate deep into surrounding tissues. This is called metastasis.

As the cancer cells invade healthy surrounding breast tissue, they can infiltrate the underarm lymph nodes – these are small filters that trap debris and other harmful substances. The lymph, the fluid in the nodes, also contains white blood cells (immune cells) that can attack germs in the fluid. Once in the lymphatic system, the cancer cells are able to reach distant parts of the body and settle there to form new tumours.

The anatomy of the breast in a nutshell

To better understand the various types of breast cancer, it helps to know that the female breast consists of:

• Lobules – The small milk producing glands. Any cancer that starts here is called a ‘lobular carcinoma’.
• Ducts – These tiny tube-like structures transport milk from the lobules to the nipple. If the cancer originates in the milk ducts, it is called a ‘ductal carcinoma’.
• Stroma – The fatty connective tissue that protects the lobules, ducts, blood vessels and lymphatic vessels.

Types of breast cancer

Ductal carcinoma in situ (DCIS)

DCIS is diagnosed when some cancer cells have developed in the ducts but are ‘staying put’ since they have not yet acquired the capacity to spread beyond the ducts; hence the term ‘in situ’.

Although this early form of breast cancer is considered to be non-invasive, it may become invasive after some years if left untreated.

Lobular carcinoma in situ (LCIS)

LCIS is another type of early abnormal breast growth that is non-invasive. As the name suggests, the collection of abnormal breast cells remain ‘in situ’ or inside the lobules and do not spread to nearby tissues.

Most women diagnosed with LCIS do not develop full-blown breast cancer.

Invasive breast cancers

Invasive breast cancer refers to cancer cells that fan out to nearby breast tissue. These cancers are classified as follows:

• Invasive ductal carcinoma (IDC)
  According to Cancer Research UK, 70 to 80% of breast cancers are diagnosed as IDC. This cancer develops in the cells that line the breast’s ducts and spreads beyond it into healthy breast tissue.
• Invasive lobular carcinoma (ILC)
  Also known as infiltrating lobular carcinoma, ILC is the second most common type of breast cancer – about 10 to 15% of breast cancers are diagnosed as ILC. In this type of cancer, the cancerous cells are able to break through the lining of the breast’s lobules and metastasise into nearby breast tissue.
• Inflammatory breast cancer (IBC)
  This rare but aggressive form of breast cancer typically begins with breast swelling instead of a lump. It grows and spreads rapidly, causing symptoms to become more severe within days or even hours. The cancer cells block the lymph channels and the breasts may become red, firm and hot to the touch.
• Paget’s disease of the nipple
  Experts believe that the cancer cells start developing within the breast ducts and eventually spread to the nipple surface. As such, women with this condition often have another cancerous area in the breast tissue. In other cases, the cells of the nipples themselves start growing abnormally.
• Phyllodes or cystosarcoma phyllodes
  This rare type of breast tumour can either be benign, malignant or in between cancerous and non-cancerous. It grows quite rapidly in a leaf-like pattern and requires surgical removal to prevent recurrence.
• HER2-positive breast cancer
  In this type of cancer, the cancerous cells test positive for the protein called human epidermal growth factor receptor 2 (HER2). Since this protein stimulates the growth of the tumour, HER2-positive breast cancers are usually more aggressive than other types of cancer.
• Triple negative breast cancer
  For breast cancer to be diagnosed as ‘triple negative’, the tumour must not have any receptors (proteins on the cells’ surface) for HER2 proteins, or for the hormones oestrogen and progesterone.

Stages of breast cancer

To describe the size and the extent of metastasis, doctors often use:

TNM staging

This considers the tumour’s size (T), whether it has infiltrated the lymph nodes (N) and if it has metastasized (M) to other parts of the body.

Number stages

• Stage 0: Carcinoma in situ.
• Stage 1: The tumour is 2cm or smaller.
• Stage 2: The tumour is either smaller than 2cm (stage 2A) or 5cm (stage 2B) and has spread to the lymph nodes, or is larger than 2cm (stage 2A) or 5cm (stage 2B), but has not spread.
• Stage 3:
  • Stage 3A – No traces of cancer can be found in the breast OR the tumour is about 5cm and has infiltrated the lymph nodes.
  • Stage 3B – The tumour has spread to the breast’s skin and lymph nodes.
  • Stage 3C – The cancer affects both the skin of the breast and the underarm lymph nodes.
• Stage 4: The cancer has now spread throughout the body.

Grading

• Grade 1 or low-grade: The cancer cells resemble normal, healthy cells, grow ‎quite slowly and are less likely to metastasise.
• Grade 2 or moderate/intermediate grade: The cells replicate faster and have an abnormal appearance.
• Grade 3 or high grade: The cancer cells grow much faster at this stage and do not resemble normal cells anymore.

For more information, we recommend you check out Cancer Research UK or Breast Cancer Care.