The Breast

Subjects covered in this chapter include anatomy, investigations of the breast, the nipple, benign and malignant disorders of the breast, breast reconstruction, screening for breast cancer, breast cancer genetics and the male breast.

Comparative and surgical anatomy

The protuberant part of the human breast is generally described as overlying the 2nd to the 6th ribs, and extending from the lateral border of the sternum to the anterior axillary line. Actually, a thin layer of mammary tissue extends considerably farther from the clavicle above to the 7th or 8th ribs below, and from the midline to the edge of latissimus dorsi posteriorly. This fact is important when performing a mastectomy, the aim of which is to remove the whole breast. The anatomy of the breast is illustrated in Fig. 46.1

The axillary tail of the breast is of considerable surgical importance. In some normal cases it is palpable, and in a few it can be seen premenstrually or during lactation. A well-developed axillary tail is sometimes mistaken for a mass of enlarged lymph nodes or a lipoma.

The lobule is the basic structural unit of the mammary gland. The number and size of the lobules vary enormously: they are most numerous in young women. From 10 to over 100 lobules empty via ductules into a lactiferous duct of which there are from 15 to 20. Each lactiferous duct is lined by a spiral arrangement of contractile myoepithelial cells and is provided with a terminal ampulla — a reservoir for milk or abnormal discharges.

The ligaments of Cooper are hollow conical projections of fibrous tissue filled with breast tissue, the apices of the cones being attached firmly to the superficial fascia and thereby to the skin overlying the breast. These ligaments account for the dimpling of the skin overlying a carcinoma.

The areola contains involuntary muscle arranged in concentric rings as well as radially in the subcutaneous tissue. The areolar epithelium contains numerous sweat glands and sebaceous glands, the latter of which enlarge during pregnancy and serve to lubricate the nipple during lactation (Montgomery’s tubercles).

The nipple is covered by thick skin with corrugations. Near its apex lie the orifices of the lactiferous ducts. The nipple contains smooth muscle fibres arranged concentrically and longitudinally; thus is an erectile structure which points outwards. Lymphatics of the breast drain predominantly into the axillary and internal mammary lymph nodes. The axillary nodes receive approximately 75 per cent of the drainage and are arranged in the following groups:

lateral, along the axillary vein;

anterior, along the lateral thoracic vessels;

posterior, along the subscapular vessels;

central embedded in fat in the centre of the axilla;

interpectoral, a few nodes lying between the pectoralis major and minor muscles;

apical, which lie above the level of the pectoralis minor tendon in continuity with the lateral nodes and receive the efferents of all the other groups.

The apical nodes are also in continuity with the supraclavicular nodes and drain into the subclavian lymph trunk which enters the great veins directly or via the thoracic duct or jugular trunk. The sentinal node is that lymph node designated as the first axillary node draining the breast.

The internal mammary nodes are fewer in number and lie along the internal mammary vessels deep to the plane of the costal cartilages.