Plastic and Reconstructive Surgery of the Breast (eBook)

1 Anatomy of the Breast

Fig. 1.1 Anatomy of the musculature covering the thoracic wall.

1 Clavicular part of the pectoralis major

2 Sternocostal part of the pectoralis major

3 Latissimus dorsi

4 Abdominal part of the pectoralis major

5 Serratus anterior

6 Rectus abdominis

7 Tendinous intersection of the rectus abdominis

8 External oblique muscle of the abdomen

Structure of the Female Breast

The female breast is roughly circular except at the upper outer quadrant, where the axillary tail of Spence extends to the axilla (Fig.1.3). The functional portion of the breast is a modified cutaneous gland, an appendage of the skin. It is enclosed between the superficial and deep layers of the superficial fascia and extends from the sternocostal junction to the midaxillary line laterally, and to the third to the sixth ribs in the midclavicular line. In the elderly or in large breasts, the submammary fold may slide to the seventh rib. The upper two-thirds of the breast lie on the pectoralis major fascia and extend laterally to the serratus anterior muscle. The lower third lies on the external oblique muscle of the abdomen and the rectus abdominis muscle.

The lobule is the basic unit of the breast (Fig.1.2). Each lobule contains 10–100 elongated terminal ducts called alveoli or acini. Ducts draining 20–40 lobules coalesce to form larger ducts and, ultimately, an excretory duct. A total of 15–20 lactiferous ducts drain the entire breast and dilate into the milk sinus beneath the areola.

The surrounding stroma consists of connective tissue, nerves, blood vessels, and lymphatic channels. Portions of the fibrous tissue of the breast parenchyma extend from the surface of the glandular breast anteriorly to the superficial layer of the superficial fascia (Cooper ligaments). Posterior ligaments suspend the breast to the deep layer and the pectoral fascia. Although the Cooper ligaments subdivide the parenchyma, there is no true surgical segmental breast architecture.

Because the Cooper ligaments are anchored in the skin, tethering of these ligaments by a small scirrhous carcinoma commonly produces a dimple or subtle deformity in the otherwise smooth surface of the breast.

With pregnancy, there is hyperplasia of the lobular units and diminution of the fibrous stroma. The normal size may be increased as much as two or three times. The nipple and areola become more prominent and more deeply pigmented. When lactation stops, the extralobular tissue involutes and the breast gradually returns to resting state. It does not return to the nulliparous form, however, and instead retains the mature shape.

Blood Supply

Three major arteries supply the breast with blood: the perforating branches of the internal thoracic artery, and the lateral thoracic and pectoral arteries (Fig.1.2). The lateral perforating branches of the intercostal arteries and branches of the subscapular artery also contribute minor amounts to the blood supply.

The arterial supply to the medial and central breast stems from the perforating branches of the internal thoracic artery. These pass through the first through the fourth intercostal space just lateral to the sternum, penetrate the origin of the pectoralis muscle, and enter the medial edge of the breast, supplying more than 50 % of the blood to the organ.

The lateral thoracic artery, the second largest source of blood to the breast, arises from the axillary artery and courses down along the lateral border of the pectoralis minor muscle to reach the serratus anterior muscle. Its external mammary branches and the lateral perforating branches of the intercostal arteries supply the lateral breast.

The pectoral artery originates at the thoracoacromial artery, coursing down between the pectoralis major and minor. It supplies the posterior surface of the breast.

The perfusion of the nipple–areola complex is particularly important during surgery for aesthetic purposes. The blood supply to this complex arises medially and cranially from the internal thoracic and intercostal arteries.

The breast skin is mainly nourished by a subdermal plexus formed by perforators from the glandular tissue. The perfusion of skin flaps depends on the conservation of the subdermal plexus, the quality of the microcirculation, and the preservation of the major arterial supply at the base of the breast. The same is true for the central breast area with the nipple–areola complex.

The breast has a rich anastomosing network of superficial subcutaneous veins that mainly drain into the internal mammary vein. The drainage of the deep veins corresponds to the arterial blood supply.

Nerve Supply

Lateral branches of intercostal nerves 3–6 supply the breast in segments. The central region of the breast, including the nipple and areola, receives its sensory supply primarily from the anteromedial and anterolateral nerve fibers of intercostal nerves T3, T4, and T5; the predominant supply, however, is from T4. When carrying out reduction mammaplasty, the surgeon should take care to spare at least one of these branches in order to preserve sensory supply. The inferior branches of the cervical plexus also contribute to the sensory supply of the superior breast. Nipple sensation should be documented prior to any surgery that might reduce sensitivity. Intraoperative injuries to the anteromedial or anterolateral segmental nerves can lead to hypesthesia or loss of sensation. Paresthesia or hypersensitivity may accompany reinnervation following partial nerve lesions. Massaging the affected area can often ameliorate the condition. The medial and inferior breast is supplied by the second through sixth lateral branches of the intercostal nerves. The lateral cutaneous branch of the second intercostal nerve (the intercostobrachial nerve) passes laterally or peripherally through the axilla and forms a plexus with the cutaneous branch of the median nerve and the third intercostal nerves. Together, these nerves supply the medial aspect of the upperarm. Preserving them may sometimes prove difficult when the axilla is dissected, as they pass through the central group of lymph nodes (Fig.1.4).

Lymphatic System

The lymph vessels of the mammary gland and their regional lymph nodes are particularly important. A distinction is made between superficial and deep layers, which communicate with each other. Lymph drainage can take place in several directions. The lymph vessels course laterally around the margin of the pectoralis major and there join the pectoral lymph nodes, which accompany the lateral thoracic vessels. These lymph nodes extend to the third digitation of the serratus anterior. From here, lymph drains into the axillary lymph nodes (superior mesenteric and interpectoral). Another lymph drainageroute passes through the pectoralis major near the parasternal line and through the intercostal spaces to the parasternal lymph nodes, which lie along the internal mammary vessels. These transport the lymph to the supraclavicular lymph nodes directly into the subclavian vein. Lymph can also drain into the supraclavicular lymph nodes via the superior mesenteric lymph nodes and via the infraclavicular nodes (the apical axillary lymph nodes) along the major vessels. Finally, there are intramuscular drainage routes, which pass through the pectoralis major directly to the nodes. These include the interpectoral lymph nodes between the two chest muscles, which drain into the deep nodes of the axilla or directly into the apical axillary lymph nodes. The lateral and intramuscular drainage lymph routes in particular are clinically significant (Fig.1.5).

Fig. 1.2 Anatomy of the vascular structures supplying the breast and their positions in the thoracic wall.

1 Subscapular artery

2 Lateral thoracic artery

3 Thoracoacromial artery

4 Internal thoracic artery

5 Brachiocephalic trunk

6 Common carotid artery

7 Subclavian artery

8 Medial mammary branches

Musculature of the Thoracic Wall

The muscle layers of the anterior and lateral thoracic wall include the pectoralis major and minor, serratus anterior, external oblique, and the origins of the rectus abdominis (Fig.1.1).

The pectoralis major covers the greater part of the anterior chest wall, significantly determining its outer contour. Laterally, it borders in the deltoid muscle and is separated from it by the deltopectoral groove. This interval continues into the upper arm as the lateral bicipital groove. The inferior margin of the pectoralis major forms the anterior axillary fold. Completely covered by the pectoralis major, the pectoralis minor extends superiorly from its origin at the third to fifth ribs to the coracoid process.

The serratus anterior covers the lateral part of the thorax. Its inferior origins alternate with the digitations of the external oblique muscle of the abdomen.

The rectus abdominis extends from its origins at the cartilage of the fifth to seventh ribs past the inferior margin of the thorax. The external oblique muscle of the abdomen arises from the inferior seventh to eighth ribs and extends to the lateral margin of the rectus...