What is Breast Cancer?
Breast cancer is when cells grow and divide in an abnormal way to form a growth or ‘tumor’.1 Although it may start in the breast, the cancer can spread to other parts of the body (metastasis), such as the liver or bones.2,3 Breast cancer can be categorized into ‘stages’ (0–4) based on where the tumor is and whether it has spread.3
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What are genetic mutations, and can they cause breast cancer?
Breast cancer can be categorised by the presence or absence of certain proteins which hormones attach to.4 This is important as hormone receptor status can influence treatment selection.4 Testing involves checking for estrogen and progesterone receptors and the amount of a growth-promoting protein called HER2.4,5 If cancers have one or both of the receptors they are known as ‘HR-positive’ (HR+) and if it has neither, HR-negative (HR-).4 Cancers with normal levels of HER2 are known as 'HER2-negative’ (HER2-) and those with higher than usual levels are ‘HER2-positive’ (HER+).5 If a cancer doesn’t have estrogen or progesterone receptors or elevated HER2, it is referred to as ‘triple-negative’ (TN).4,5
The adjacent pie chart shows that ‘HR+, HER2-‘ is the most common and ‘HR-, HER2+’ is the least common hormone receptor status.6
Proportion of breast cancers with each hormone receptor status6
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