Anatomy of the Female Breast
Boundaries and Borders
- The female breast lies over the 2nd - 6th rib.
- Two-thirds of it rests on pectoralis major.
- One-third of it lies on the serratus anterior.
- The lower medial edge of the breast overlaps the upper part of the rectus sheath.
- The breast consists of 15-20 lobules of grandular tissue embedded in fat.
- It consists of fat, fibrous tissue and glandular tissue.
- The ligaments of Cooper (fibrous septa running from the subcutaneous tissue to the fascia of the chest wall) separates the breast lobules.
- The nipple is surrounded by the pigmented areola.
- Each lobule drains by its lactiferous duct on to the nipple.
- The areolar glands of Montgomery lubricate the areola. These are large, modified sebaceous glands.
Blood supply of the breast
Blood supply of the breast is principally via through these main arteries:
- Axillary artery - via its lateral thoracic and acromiothoracic branches
- Internal thoracic artery (former name: Internal mammary artery) - via its perforating branches.
- Intercostal arteries - via their lateral perforating branches.
The venous drainage corresponds to the arteries mentioned above.
Lymphatic drainage of the breast
A good knowledge of the lymphatic drainage of the breast is vital in understanding the spread of breast tumours.
The main pathways of lymphatic drainage of the breast follow the venous drainage - to the axilla and to the internal thoracic chain.
- 75% of the total lymphatic drainage of the breast is accounted by the axilary lymph nodes (20-30 in number).
- the internal thoracic nodes also receive lymphatics penetrating along the lateral perforating branches of the intercostal vessels.
- The lateral part of the breast tends to drain toward the axilla and the medial part of the breast towards the internal mammary chain.
Axillary lymph nodes
This can be divided into five groups:
- Anterior: Lying deep to pectoralis major along the lower border of pectoralis minor
- Posterior: Along the subscapular vessels
- Lateral: Along the axillary vein
- Central: In the axillary fat
- Apical: These arises behind the clavicle at the apex of the axilla along the medial side of the axillary vein and above the pectoralis minor.
All other axilllary lymph nodes drain into the apical lymph nodes. The subclavian lymph trunk emerges from the apical nodes.
Right: The right subclavian lymph trunk drains either directly into the subclavian vein, or joins the right jugular trunk.
Left: The left subclavian vein drains directly into the thoracic duct.
Internal Thoracic (Internal Mammary) Nodes
- The internal thoracc nodes lie next to the sternum, along the internal thoracic vessels. They drain into the mediastinal nodes: to the thoracic duct on the left and to the right thoracic duct on the right.
- Inferiorly, they communicate with the groin nodes via lymphatics that accompany the superior and inferior epigastric vessels.
The Male Breast
- It comprises of small ducts supported by fibrous tissue, without alveoli.
- However, it is still prone to the major diseases that affect the female breast.
- Although it is rare, 300 men in the UK are diagnosed with breast cancer each year.
Applied Clinical Anatomy
- Skin dimpling: Malignant infiltration and fibrous contraction of Cooper's ligaments results in dimpling over the skin of the breast. When this clinical finding is noted, malignancy should always be suspected. This may also occur in chronic infection, post-trauma, and very rarely, in fibroadenosis.
- Nipple retraction: This is suggestive of milk duct involvement in the fibrous contraction of a scirrhous tumour.
- Oedema of the arm after mastectomy usually occurs only if lymph drainage is damaged by infection, malignant infiltration, heavy irradiation by radiotherapy or if additional strain is put on the evacuation of fluid from the limb by ligation or thrombosis of the axillary vein.
- Breast carcinoma tends to infiltrate normal pathways of lymphatic drainage. Following that, it may spread to the lymphatics of the opposite breast, contralateral axillary lymph nodes, inguinal and cervical lymph nodes.
- Breast incisions should be made radially to avoid cutting across the line of the ducts
- A galactocoele is caused by blockage of a duct causing dilatation.
Common Developmental Abnormalities
- Failure of nipple eversion: It is important to ask the patient if an inverted nipple is a recent change or has it been present since birth.
- Supernumerary nipples or even breasts may occur along a verticle milk like.
- Amazia: small or absent breasts on one or both sides
- Ellis H, Mahadevan V. Clinical Anatomy: Applied Anatomy for Students and Junior Doctors (12th Edition). Wiley Blackwell; 2010.