Fig. 1.1
Illustration of milk (ridge) line
The glandular component of the breast develops from the ectoderm. It arises from local thickening of the epidermis, 15–20 groups of ectodermal cells grow into the underlying mesoderm (dermis) during the 12th week of gestation. These groups of cells then develop spaces that will become the lactiferous ducts. The nipple initially develops as a shallow epidermal indentation which becomes everted near term.
The connective tissue stroma of the breast forms from the mesoderm, which also forms the dermis of the skin and the superficial fascia. Fibres forming the Cooper’s suspensory ligaments develop from both layers. At birth males and females have the same breast anatomy. In the female, at puberty, hormonal stimuli cause the breast to develop, initially oestrogen causes fat to be deposited in the breast, and the lactiferous milk ducts to enlarge.
Following the onset of menstruation the ovaries begin to produce progesterone and this causes lobules and acini or milk glands to develop at the ends of the lactiferous ducts. The breasts develop from the buds sited bilaterally on the anterior chest wall overlying the pectoralis major muscle and once formed will lie between the 2nd to 6th ribs vertically and from the sternum medially to the mid axillary line laterally. The process of development usually takes about 3–5 years.
Male breast development, when present, is termed gynaecomastia. This condition arises as a response to hormonal imbalances which can occur at puberty or in later life as a result of disease, medication, recreational drug use or excessive alcohol consumption. The condition is investigated in the same way as female breast disease utilising mammography and ultrasound. Pseudogynaecomastia occurs when fat is deposited on the anterior chest wall under the nipple areolar complex and looks very similar outwardly to true gynaecomastia, however, in gynaecomastia proper breast tissue development is evident, in pseudogynaecomastia the enlargement is purely due to adipose tissue.
Macroscopic and Microscopic Anatomy
Once fully developed the breast is ‘tear drop’ shaped. The breast itself can be described in terms of both its external and internal composition and by its macroscopic and microscopic anatomy.
Externally the breast comprises of:
The nipple
The areolar
Skin
Inframammary Fold
Montgomery’s Glands (Tubercles)
Internally the breast comprises of:
Glandular Tissue – 15–20 lobes
Lactiferous Ducts
Lactiferous Sinuses (Ampullae)
Terminal Ductal Lobular Units (TDLU)
Adipose Tissue
Superficial Fascia
Deep Fascia
Retromammary Space
Cooper’s Ligaments
Blood vessels
Figure 1.2 illustrates the gross anatomical structures of the breast
Fig. 1.2
Overview of external and internal breast anatomy (Reprinted with permission from: Shiffman MA, Di Giuseppe A. Cosmetic Surgery. Springer, 2013)
It is important to understand the external anatomy when positioning the breast for mammography and the internal anatomy when assessing the mammographic image. On mammography the fat contained within the breast is radiolucent whilst the glandular component appears as areas of increased density.
Macroscopic Anatomy
The breast can be macroscopically divided into two main parts. The glandular component is the first of these and is concerned with milk production. The second part consists of all the other tissues that make up and support the breast. These include fat, fascia (connective tissue), and muscles.
Breast tissue extends into the low axilla as a triangular shaped projection – this portion of the breast is called the axillary tail or ‘Tail of Spence’. The glandular component consists of 15–20 lobes which radiate out from the nipple. Each one of these is made up of 10–100 lobules which contain multiple acini – where milk is produced and stored during lactation.
These are drained by a network of small ducts (intralobular ducts) which come together to form a single duct draining each lobule (interlobular duct). The interlobular ducts in turn join to form intralobar ducts which jointly form a single lactiferous duct which drains that lobe. The purpose of the ducts is to transport milk; the lactiferous ducts dilate just under the nipple to form the lactiferous sinus or ampulla and then narrow and terminate at the surface of the nipple. The lobes are separated by fibrous septae and connective tissue stroma.
The skin overlying the breast is typically 0.5–2.0 mm in thickness. Beneath the skin is a superficial layer of fascia that divides into the superficial and deep layers as it reaches the breast. Between these layers the breast proper develops. The deep layer of fascia lies directly on the fascia of the pectoralis major muscle. This allows slight movement of the breast on the chest wall. The breast is supported by the Cooper’s ligaments, and also by the skin, deep and superficial layers of the fascia and pectoralis major muscle. The superficial fascia is covered by a layer of adipose tissue 2–2.5 cm thick and is attached to the skin by the Cooper’s Ligaments which pierce the fat. The retro mammary space lies between the deep fascia of the breast and the fascia of the pectoralis major muscle and is filled by loose connective tissue. The main internal components of the breast and the corresponding mammographic features are demonstrated in Fig. 1.3.
