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.
•
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.