Breast cancer is the abnormal growth of cells in the breast. These cells grow and develop into a cancerous growth that can have the potential to spread to other parts of the body.

Breast cancer is the most common cancer among Singaporean women. ¹

More than 25% of all cancers diagnosed in women are breast cancers. Between 2011 and 2015, about 1 927 women were diagnosed with breast cancer in Singapore each year.²

There is no single cause of breast cancer, however there are a number of risk factors that can increase your chance of developing breast cancer including genetic, lifestyle and environmental factors.

These can include:

• Gender – being female increases your risk
• Having a family history of, or close relative who has had, breast cancer
• Aging – women who are 50-years-old are 10 times more at risk to develop breast cancer than women who are 30-years-old ¹¹
• Drinking alcohol ¹¹
• Being overweight

In 5-10% of cases, breast cancer is hereditary. The cancer is caused by specific gene mutations (changes) in the BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two) genes.² There are several other genes other than BRCA1 and BRCA2 that also help make up this percentage.

These genes can develop abnormally which may then be passed down through family generations, increasing the chance of breast (and ovarian) cancers.²

Following consultation and physical examination by your doctor, you may receive a number of tests to assist in diagnosing breast cancer. This may include a:

• Mammogram
• MRI scan
• Ultrasound
• Biopsy

Breast cancer is typically classified into stages from 0 – IV based on:

• tumour size (T)
• if the cancer has involved any lymph nodes (N)
• whether the cancer has metastasised (spread) to other parts of the body (M).³

There are many different types of breast cancer, some of which are common, while others are very rare. Some of these include:

• Invasive ductal carcinoma (IDC) – IDC is the most common type of breast cancer. Invasive means that the cancer has begun to invade breast tissue close to where it originated. In the case of IDC, the cancer began in the milk duct and has now spread through the duct wall to other breast tissue.
• Invasive lobular carcinoma (ILC) – Rather than beginning in the milk duct, ILC originates in the milk glands (known as lobules) and invades nearby areas of the breast.
• Inflammatory breast cancer (IBC) – Unlike other types of breast cancer, IBC does not involve a lump in the breast. Instead, the skin of the breast may become red, inflamed, thick or pitted (like an orange), your nipple may become inverted, and the breast may become swollen, hard, tender and painful, or itchy. IBC is a rare type of breast cancer and is more likely to be advanced upon diagnosis, as it is difficult to identify using a mammogram.

Following a breast cancer diagnosis, further testing is then conducted to identify the receptor status of the cancer. Cancers will be classified as hormone receptor positive or negative depending on whether they have proteins that are oestrogen or progesterone receptors. Your breast cancer may be classified as ER+ (has oestrogen receptors), PR+ (has progesterone receptors), HR+ (has one or both of these receptors) or HR- (has neither of these receptors). Your cancer may also be classified as HER2 positive or negative. HER2 is a protein which promotes the growth of cancer cells and in HER2 positive breast cancer, there are higher than normal levels of HER2.

• HR positive HER2 negative breast cancer – This is the most common form of breast cancer. A HR+ HER2- classification means the cancer has oestrogen or progesterone receptors but does not overexpress the gene HER2. It is typically treated using hormone therapies.
• HER2 positive breast cancer – 25% of all breast cancers are HER2-positive, which is more common in women below the age of 60. HER2 positive breast cancer often spreads faster than other breast cancers, but responds well to treatments that target the HER2 protein (known as targeted therapies).
• Triple negative breast cancer – Triple negative breast cancer accounts for 15% of all breast cancer cases and is an invasive breast cancer. It is classified as triple negative because it does not have the three proteins that are typically found on breast cancer cells: oestrogen, progesterone and HER2 receptors. It is more common in women younger than 40 or who have the BRCA1 gene mutation.