Introduction

To successfully address the vast array of aesthetic and reconstructive procedures requires a thorough understanding of breast development and anatomy. Surgical techniques including breast augmentation, post-mastectomy reconstruction, mastopexy and reduction mammaplasty require comprehensive understanding of both the normal or ideal anatomy as well as pathologic or variant presentations. The normal appearance of the breast is a vital aspect of the female form. Knowledge of breast anatomy facilitates safe and effective surgical management.

Ideal breast architecture

The appearance of the ideal breast is somewhat subjective. Each patient has their own opinion as to the aesthetics of their breasts, which should be given consideration with any operative alteration of the breast. Reconstruction or cosmetic enhancement of the breast encompasses not only the way the breast looks, but also how it feels to the touch. Size, symmetry, proportionality and the location of the breast and its landmarks on the chest wall all play a role in the attractiveness of the breast. Statistical standards for the dimensions of the breast have been analyzed and reported by various authors (Fig. 1.1).¹^–⁷ The distance from the sternal notch to the nipple and the distance from the midclavicular line are each 19–21 cm. The distance from nipple to the inframammary fold is 5–7 cm (Fig. 1.1). The distance from the nipple to the midline is 9–11 cm. These measurements offer guidelines for altering the breast, which must be individualized, based on proportionality, variances in chest wall anatomy, posture and patient preference (Fig. 1.2).

Fig. 1.1 Statistical standards for the dimensions of the breast.

Fig. 1.2 AP image: ideal breast dimensions demonstrating symmetry and projection.

The breast mound is situated over the pectoralis major muscle between the second and sixth ribs in the nonptotic state. Important landmarks include the upper pole, location of the nipple areolar complex, inframammary fold and lateral breast fold. The upper pole of the breast extends from just below the clavicle to the level of the nipple. The contour should be neither concave nor convex, but a plane that extends out to the point of maximum projection of the breast at the level of the nipple. In the ideal breast form, the nipple areolar complex should be cephalad to the level of the inframammary fold.

Development of the breast

The breast originates from the ectoderm, the germinal layer which forms the initial breast bud. The connective tissue is derived from the mesoderm. A group of glands, derived from the epidermis, develops within the dermis and underlying fascia. Breast development occurs along the milk line, which extends from the axilla to the groin. The normal breast develops at the level of the fourth intercostal space on the anterolateral chest wall. Supernumerary breast formation can occur anywhere along the milk line (Fig. 1.3). The most common location of supernumerary breast formation is at the inframammary crease on the left side, but additional breast formation can occur in the axilla as well.

Fig. 1.3 The milk lines.

(Reproduced with permission from Standring S, ed. Gray’s anatomy, 40th edn. London: Churchill Livingstone; 2008.)

Following a brief period of activity shortly after birth in response to maternal hormones, breast development is quiescent until puberty. Onset of puberty occurs at approximately 9 years of age (Fig. 1.4). Typically, by age 14, parenchymal growth has extended to its mature borders. These include the clavicle at the superior border, the sternum at the medial border, the inframammary fold for the inferior border and the anterior border of the latissimus dorsi for the lateral border. Breast tissue can extend beyond the borders particularly medially and inferiorly. The breast tissue that extends laterally through the axillary fascia into the axillary fat pad is referred to as the “tail of Spence.” Mature breast morphology projects from the chest wall in a conical fashion with its greatest point of projection at the nipple areolar complex (Fig. 1.5).

Fig. 1.4 Stages in breast development. Pre-and post-pubertal development and structure of the female breast, demonstrating changes in the contour of the breast.

(Reproduced with permission from Standring S, ed. Gray’s anatomy, 40th edn. London: Churchill Livingstone; 2008.)

Fig. 1.5 (A) Structure of the breast. (B) Changes in the breast during lactation. (C) Section of the nipple. (D) Cross-section of the nipple. There is a corrugated layer of stratified squamous keratinized epithelium over the nipple surface; 20 or more lactiferous ducts (L) open onto the surface; sebaceous glands (S) are deep to the epidermis.

(A–C, Reproduced with permission from Standring S, ed. Gray’s anatomy, 40th edn. London: Churchill Livingstone; 2008; D, from Kerr JB. Atlas of functional histology. London: Mosby; 1999, with permission from Dr JB Kerr, Monash University.)

Development of breast shape is dependent on many factors, including fat content, volume, muscular and skeletal contour and skin and connective tissue compliment. In particular, the Cooper’s ligaments provide structural support for the breast parenchyma. These structures combine to provide the final breast shape; it is dependent in large part on heredity and will change with age as the suspensory structure become lax and the breast becomes more ptotic (Fig. 1.6).

Fig. 1.6 Lateral pseudo ptosis. IMF, inframammary fold.

Parenchyma

The glandular tissue of the breast is dispersed through a significant amount of adipose tissue.⁸ The glands themselves consist of millions of lobules clustered together into 20–25 lobes. Interlobular ducts join to form approximately 20 primary lactiferous ducts that open onto the nipple areolar complex. The lactiferous ducts converge into a specialized ductile network, which stores the milk prior to lactation. The glandular parenchymal ducts are lined with cuboidal cells which transition to stratified squamous epithelium in the ductile and sinus network (Fig. 1.5).

The functioning parenchyma produces milk in the post-partum period. Adipose tissue comprises a significant amount of the breast volume, representing 50–70% of the breast volume. With age and the hormonal changes of menopause, the glandular tissue of the breast involutes, increasing the adipose to parenchymal tissue ratio. The consistency of the breast softens with the increased fatty tissue accumulation.

An intricate fascial layer supports the breast tissue. The parenchyma is fixed in placed by the superficial fascial system, which extends cephalad from the abdomen, diverges into a superficial and deep component enveloping the breast tissue and maintaining its attachment to the breast wall (Fig. 1.7). The superficial fascial layer is an extension of Scarpa’s fascia, which envelopes the glandular tissue deep to the dermal layer. The superficial fascial layer and the dermis can be difficult to distinguish. Subcutaneous fatty tissue between the dermis and the superficial fascia distinguish the two layers. The deep layer diverges at the level of the sixth rib, where the inframammary fold is the inferior border of the parenchyma.