Download BREAST ANATOMY

BREAST ANATOMY

Ideal breast is said to be conical in shape and lies between 2nd and 7th ribs (6 to 8).
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Extends from the parasternal area to the AAL.
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2/3 rests on pect major; 1/3 on Serratus anterior. Inferiorly it may overlap the superior rectus sheath
and the first digitation of the external oblique.
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The nipple lies just lateral to the MCL at the level of the 4ICS, level with the IMC and about 2 to 3 cm
below the midhumeral position.
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The breast consists of:
1. glandular tissue
2. fatty tissue
3. fibrous (septal) tissue.
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About 20 lobes drain via lactiferous ducts which enter a lactiferous sinus and then drain out.
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The areola contains apocrine sebacceous glands (of Montgomery), that are rudimentary mammary
lobules.
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The axillary tail (of Spence) is a supero-lateral extension of the breast that passes through an opening
in the axillary fascia, the foramen of Langer, to lie under the deep fascia (as opposed to the rest of the
breast which is superficial to this layer).
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The superficial fascia is continuous with the superficial abdominal fascia of Camper and consists of two
layers: the superficial layer of the superficial fascia, which is the outer layer covering the breast
parenchyma, and the deep layer of the superficial fascia, which forms the posterior boundary of the breast
parenchyma and lies on the deep fascia of the pectoralis major and serratus anterior muscles.
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Deep layer of superficial fascia is continuous with Scarpa’s fascia, Coopers ligaments connects this
fascia to the overlying dermis.
Fascial layers of the breast
EMBRYOLOGY
A.) BLOOD SUPPLY OF THE BREAST
The breast receives blood from 4 sources:
1. Internal thoracic perforators:
60% of supply (upper medial quadrant).
2. Lateral thoracic artery:
30% of supply (upper outer quadrant).
3. lateral/ medial intercostal arteries:
10% of supply (lower lateral quadrant).
4. Minor sources:
from axillary, subscapular, thoracodorsal and thoracoacromial
1. Upper 4 anterior perforating mammary branches of internal mammary (thoracic) artery
The main blood supply to the breast, especially to the upper and medial aspects of the breast. These
perforating branches pass through the pectoral muscles to supply the breast. [The internal thoracic artery
arises from the first part of the subclavian, passes down + 1cm lateral to the lateral edge of the sternum and
ultimately splits into its terminal branches: the sup epigastric and the musculophrenic.]
Two rows of perforators here – medial and lateral
2. Branches of lateral thoracic (external mammary) arteries.
The lateral thoracic artery is usually a branch of the second part of the subclavian artery
Supplies upper/lateral parts of the breast, with the mammary branches, it supplies 75% of blood to the NAC.
3. intercostal perforating arteries (3rd, 4th and 5th)
Lesser blood supply.
B.) VENOUS DRAINAGE OF THE BREAST
Venous drainage is by 2 main avenues:
1. Superficial System
_ Transverse vessels are located subcutaneously and medially and drain into the internal thoracic veins.
_ The longitudinal system drains cephalad into the lower neck veins.
2. Deep drainage system
Located in the chest wall in the intercostal veins that drain into vertebral, azygos, SVC, axillary.
C) LYMPHATIC DRAINAGE OF THE BREAST
4 Main routes:
1. Cutaneous
2. Internal thoracic
3. Posterior intercostal
4. Axillary
 Skin of the breast and the underlying parenchyma, which originate embryologically in the ectoderm, share
the same lymphatic drainage
 3 plexuses
1. Lymphatic capillaries lie in the superficial dermis surrounded by compact fibroareolar tissue,
deep to the dermal arterioles and superficial to the venules
2. Deeper in the dermis, valved collecting lymphatic trunks pass into the subcutaneous tissues
parallel to the lymphatics of the subcutaneous fatty tissue.
3. Subcutaneous lymphatics
 Drainage patterns:
1. lateral half drains mostly into pectoral nodes along the lateral chest wall then into central and
apical nodes and finally via subclavian trunks into the larger lymphatic ducts.
2. Drainage from the medial half flows to parasternal nodes inside the chest cavity on either side
of the sternum which then drain into bronchomediastinal trunks
3. Some drainage from the inferior region flows along the anterior abdominal wall to the inguinal
nodes in the groin.
 Most of the breast lymph flows to the axillary nodes (75%)

5 Groups of axillary nodes:
a. Pectoral nodes receive lymph drainage from the breast and anterior chest wall
b. Lateral nodes receive most of the lymph from the upper extremity except those following the
cephalic vein
c. Subscapular nodes receive lymph from the posterior body wall and scapular region
d. Central nodes receive drainage from the above three groups; it is then passed to the
e. Apical nodes which then drain into the subclavian trunk which was described previously
D.) INNERVATION OF THE BREAST (Sarhadi/Soutar BJPS 1996 and Schlenz PRS 2000)
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breast receives innervation from the lateral and anterior cutaneous branches of the 2nd–6th intercostal
nerves, along with a contribution from the supraclavicular nerves.
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T2 and T6 innervates breast skin only
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Lateral cutaneous branches always larger than anterior branches
Nipple supply
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all neural elements are concentrated at the base of the nipple, only few at the side of the nipple, and
practically none in the areola.
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NAC receives from lateral and anterior cutaneous branches of the 3rd–5th intercostal nerves which joined
a plexus in the subdermal region, although the main supply is from T4 - sole supply in 79% but involved
in 93%
Nerve supply of breast
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Lateral cutaneous branches
o divides into anterior and posterior divisions. Posterior divisions supply the back
o anterior division pierces the deep fascia/serratus anterior in the midaxillary line and follows an
inferomedial course within the pectoral fascia or the pectoral muscle (one breast). On reaching the
midclavicular line, they turned for almost 90 degrees and continued through the glandular tissue
toward the posterior surface of the nipple, which they entered with several tiny branches
o The anterior division of T4 lateral branch divides into 2 branches (superficial and deep) that
supply the nipple
o Deep branch passes through the submammary space and loops through the inferolateral part of the
breast before passing through the superficial fascia to reach the areola and nipple.
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anterior cutaneous branches
o T3-T5 contributed to the medial innervation of the nipple-areola complex.
o T3(82%) is the more constant supply here than T4 (78%).
o After piercing the fascia in the parasternal line, they divide into a lateral and a medial branch.
o The medial branch supplies the sternum
o The lateral branch divides intoseveral smaller branches that took an inferolateral course through
the subcutaneous tissue towards the areolar
4th lateral cutaneous branch supply to nipple
Summary of NAC innervation

Supplied by anterior and lateral branches of T3-T5
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T4 is the main supply in the majority of cases
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Lateral branches of T4 mainly travel deep to the pectoralis fascia
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Anterior branches always took a superficial course in the subcutaneous tissu