Breast cancer is the most diagnosed cancer worldwide and accounts for the most cancer-related deaths among women. It is a multifactorial disease that can be categorized into three subtypes according to the hormone receptor (HR) status — oestrogen receptor (ER) and/or progesterone receptor (PR) expression — and human epidermal growth factor receptor 2 (HER2) status. Each subtype determines the prognosis and choice of treatment.

The authors declare no competing interests