Breast cancer can arise in a number of different tissues. Lobules and terminal ducts are where most breast cancers start. Lobules are the milk-producing glands clustered in 15-20 sections called lobes, while ducts carry the milk to the nipple at the centre of the areola.⁴

Blood vasculature and fat cells lie between lobules and ducts with adipose tissue covering the lobes. Lymph vessels link to lymph nodes found in the armpit, above the collarbone, in the chest and elsewhere.

Breast tissue extends to the underarm area meaning breast cancer may develop seemingly unconnected to the breast. The skin over the breast should also be examined for changes during a breast exam.

Male breast structures are very similar to those in the female breast but lack the specialised lobules for producing milk.