Types of breast cancer

There are several different types of breast cancer.

• Cancers that remain confined to the lobes and the ducts of the breast are called ‘non-invasive’ or ‘in situ’. 

• An ‘invasive’ cancer is one where the cancer cells have moved outside the ducts and the lobes into the surrounding breast tissue. 

• Advanced breast cancer is when the cancer has spread from the breast itself to the areas surrounding the breast (e.g. the chest) and/or to other organs in the body (e.g. lungs, liver). 

• Breast cancers can also over-express (have too many of) certain receptors.

• ErbB2-positive breast cancer (also known as HER2-positive breast cancer) is breast cancer in which the cancer cells over-express ErbB2 (HER2) receptors, a member of the ErbB family of receptors. When naturally-occurring growth factors in the body attach to the ErbB receptors, the cancer cells are stimulated to divide and grow.11 About 25% of women with breast cancer have ErbB2-positive tumours. ErbB2-positive breast cancer tends to be more aggressive than ErbB2-negative disease and patients have a poorer prognosis.

• Hormone-sensitive breast cancer (also known as hormone-responsive breast cancer or hormone-receptor-positive breast cancer) is breast cancer in which oestrogen (ER) and/or progesterone receptors (PgR) are over-expressed in the tumour (i.e. a significant number of the cancer cells have receptors for these hormones). Approximately 65% of breast cancer patients are oestrogen-receptor-positive (ER+) and/or progesterone-receptor positive (PgR+), and this is more common in older, postmenopausal women. Of these, a significant proportion (about 20 to 25%) are also ErbB2-positive.2 Around 15% of all patients with metastatic breast cancer have hormone receptor and ErbB2-receptor co-positive (HR+ / ErbB2+) disease. Such patients have an aggressive form of breast cancer and often show reduced sensitivity to hormonal therapy.