The Breast (Mammary Gland)

Key points

• • The breast is a modified skin gland of the apocrine type lying on the pectoralis major muscle, made of glandular lobes that drain by ducts to the nipple and set in fat.
• • It is anchored to the skin by fibrous bands (the suspensory ligaments of Cooper), and when a cancer tugs on these the overlying skin dimples.
• • Its blood supply comes from branches of the internal thoracic, axillary and intercostal arteries.
• • Most of its lymph (about three-quarters) drains to the axillary lymph nodes, which is why these nodes are assessed (often first by sentinel node biopsy) in breast cancer.
• • Some lymph from the inner part drains to the internal thoracic (parasternal) nodes, offering a route for cancer to reach the other breast or the chest.
• • The axillary tail of the breast extends up into the armpit, so breast tissue, and its cancers, can appear there.