General anatomy (Figs 9.1, 9.2)

The breast (Figs 9.1 and 9.2) overlies the second to sixth ribs on the anterior chest wall. It is hemispherical with an axillary tail (of Spence) and consists of fat and a variable amount of glandular tissue. It is entirely invested by the fascia of the chest wall, which splits into anterior and posterior layers to envelop it. The fascia forms septa called Cooper’s ligaments, which attach the breast to the skin anteriorly and to the fascia of pectoralis posteriorly. They also run through the breast, providing a supportive framework between the two fascial layers. The pigmented nipple projects from the anterior surface of the breast. It is surrounded by the pigmented areola and its position is variable, but it usually lies over the fourth intercostal space in the non-pendulous breast.

Figure 9.1 • Breast: sagittal section.

Figure 9.2 • Breast: anterior view demonstrating relationship to chest wall, blood supply and lymph drainage.

Lobular structure (Fig. 9.3)

The internal architecture of the breast is arranged into 15–20 lobes, each of which is drained by a single major lactiferous duct that opens on to the nipple. Each lobe is made up of several lobules, each of which drains several acini. The lobules drain via a branching arrangement of ducts to the single lobar duct. Each lobule drains several acini – these are blind saccules into which milk is secreted during lactation. The glandular tissue of the acini and the ductal tissue draining them comprise the breast parenchyma. The fat surrounding the parenchymal structures and the fibrotic framework of the breast constitute the stroma. The relative abundance of parenchyma and stroma varies according to age, parity and other factors.

Figure 9.3 • Lobular structure of breast.

Blood supply (Fig. 9.2)

The blood supply to the breast is composed of the following:

Venous drainage accompanies the arteries to the axillary and subclavian veins and the azygos system.

Lymphatic drainage (Fig. 9.2)

There are superficial lymphatics under the skin of the breast and a particular concentration in the subareolar plexus, beneath the nipple. Lymph flows unidirectionally from superficial to deep in the breast to the perilobular and deep subcutaneous plexus. Lymph in the deep plexus then drains centrifugally from the nipple to the axillary and internal mammary chains. However, the majority of drainage is to the axillary chain, with less than 5% draining to the internal mammary chain.

The axillary lymph nodes are arranged in groups, arbitrarily referred to as levels. Level I nodes lie lateral to the lateral border of pectoralis minor. Level II nodes lie behind pectoralis minor. Level III nodes lie medial to the medial border of pectoralis minor. Nodes may also lie in the breast tissue. The most common location is in the upper outer quadrant and axillary tail.

The internal mammary nodes lie in the intercostal spaces in the parasternal location, adjacent to the internal mammary vessels in the extrapleural fat.

Clinical/radiology pearl

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related posts:

The spinal column and its contents The abdomen The central nervous system The upper limb The lower limb The thorax

Stay updated, free articles. Join our Telegram channel

Join