The breast develops initially as a ventral ectodermal thickening along the so-called ‘milk line’ in mammals (Figure 1.1). Through a process of regression and maturation, discrete collections of nascent breast progenitor cells collect at specific sites along this milk line. This line extends from the axilla all the way down to the groin. Occasionally full regression fails to occur and ectopic breast formation outside of the usual location at the fourth intercostal space can develop anywhere along this line. Most commonly this is represented as an accessory nipple located at the left inframammary fold (Figure 1.2 A,B). Occasionally, a surprisingly well-formed rudimentary areola can form in association with the ectopic nipple (Figure 1.2 C). Also, it is not unusual for some women to undergo actual accessory breast parenchymal development. This usually occurs in the axilla, either unilaterally or bilaterally, and may or may not be associated with an overlying nipple or areola rudiment. This tissue can actually enlarge during pregnancy to the point where surgical excision is desired once the post-gestational period is reached (Figure 1.3 A–D). Typically, however, the breast bud located at the fourth intercostal space eventually develops on each side into the mature breast. Development starts with the onset of puberty, usually around the age of 11 or 12, and variably continues through the teenage years. Generally speaking, initial primary breast growth is completed by the age of 18 to 20. Subsequent secondary changes in the size and shape of the breast then continue under the influence of a wide variety of causes including pregnancy, weight gain or loss, hormonal changes, aging and breast-feeding. The net result is that the breast undergoes an evolution of change in appearance over the life of a woman. It is important for the aesthetic surgeon to understand this evolution when surgical alterations in breast size or shape are considered. Certainly, how the breast looks today may not necessarily be how the breast looks in ten years. Understanding and, when possible, predicting these changes can greatly improve the results of aesthetic breast surgery.

Figure 1.1 The ‘milk line’ extends from the axilla to the groin. At puberty, aberrant breast and/or vestigial nipple and areola development can occur anywhere along this line.

Figure 1.2 (A,B) An accessory nipple located just below left inframammary fold. (C) A rudimentary nipple and areola located on the breast just above the right inframammary fold along the embryonic ‘milk line’.

Figure 1.3 (A,B) Preoperative appearance of a woman with persistent unilateral aberrant axillary breast development after pregnancy. (C) The involved skin and underlying gland is marked for excision. (D) Final appearance after local excision of the involved tissue.

Understanding of the arterial anatomy of the breast is enhanced when it is realized that this anatomy is in place and fixed before the breast even begins to develop. Essentially, it is the vascular anatomy of the chest wall. Then, as the breast begins to enlarge, the available arterial and venous supply simply grows with the breast. As a result, the blood supply of the breast is diffuse and comes from a variety of potential sources including the internal thoracic artery via large anteriorly located intercostal perforators, the lateral thoracic artery, branches from the thoracoacromial axis through perforators running through the pectoralis major muscle, and anterior and posterior branches from the intercostal arteries, particularly branches from the 5th and 6th intercostal spaces (Figure 1.4). As a result, the breast can be accessed through many different incisions using a host of variably oriented pedicles and still have blood supply to the NAC preserved. Despite this diffuse blood supply, it is helpful to note that the dominant blood supply to the breast comes from the internal mammary system. These perforators off the internal mammary have an impressive pressure head due to their proximity to the heart, as anyone who has done a free flap anastomosis to the internal mammary can attest. Also, the internal mammary perforators interconnect with all other vascular sources to the breast. For this reason, throughout this book, many of the described procedures will preserve the internal mammary perforators whenever possible. The versatility these vessels provide allows division of all other vascular sources without risk of tissue necrosis.

Figure 1.4 The arterial supply of the breast.

The patterns of venous drainage mirror the arterial inflow. However, the superficial venous system is well developed and, in some patients, can often be prominently visualized through the skin. During surgical procedures, preservation of this superficial venous network is performed whenever possible as this may prevent venous congestion postoperatively. It is important to note that patients who have a prominent superficial venous arcade preoperatively may experience a distressing increase in the prominence of these vessels after a procedure such as a breast augmentation. Discussing these types of issues preoperatively may head off disappointment after the procedure if patients are adequately informed ahead of time.

The lymphatic drainage of the breast is also diffuse and variable. Traditionally recognized lymphatic basins include the axillary nodes as well as the nodes along the internal mammary vessels. Typically, while aesthetic breast procedures may interrupt some lymphatic channels in the breast, the drainage pattern is diffuse enough that there are essentially no untoward sequelae to lymph drainage of the breast after cosmetic breast surgery. Certainly, as opposed to reconstructive breast surgery, because the lymph nodes are left largely undisturbed by nearly any type of aesthetic breast procedure, lymph flow proceeds unimpeded and does not become an issue postoperatively.

In keeping with the tone set by the vascular supply to the breast, the innervation of the breast is also diffuse and variable. Multiple nerve branches from the lateral and anterior cutaneous branches of the 2nd through 6th intercostal nerves as well as the supra­clavicular nerves enter and ramify within the breast (Figure 1.5). As for the all-important innervation to the NAC, the anterior and lateral branches of the intercostal nerves and, in particular, the lateral branch of the 4th intercostal nerve tend to ramify predominantly to the subareolar plexus, although lesser and variable contributions from other surrounding intercostal nerves also ramify to the area. Generally speaking, the contributions of the lateral branches are more significant than the smaller anterior branches. The location of the nerves within the breast varies as well. After passing through the intercostal spaces, the nerves ramify within the breast, sometimes passing along the deep fascia, sometimes passing superficially through the substance of the breast. Clearly, many of the various pedicle procedures for mastopexy and breast reduction will inevitably disrupt some nerve fibers. In addition, creating a pocket under the breast for the placement of an implant will also sever some nerve fibers. If possible, every effort should be made to avoid injury to the main anterior and lateral nerve branches as they pass through the intercostal spaces anteriorly and laterally and enter the breast. Once in the breast, inevitable severing of nerve fibers must be accepted as a consequence of surgically altering the breast.

Figure 1.5 The innervation of the breast.

The mature breast demonstrates both a superficial and a deep fascial support system. Essentially, the breast bud develops within Scarpa’s fascia as it extends up onto the chest wall and the fascia splits to form an anterior and posterior lamella. Anteriorly, this lamella serves as a dissection plane for many surgeons when performing a mastectomy. The posterior lamella separates the breast from the underlying pectoralis major muscle and serves as the plane of dissection for subglandular breast augmentation. Within the breast, between these two lamellae lie interdigitating connec­tive tissue fibers extending throughout the breast (Cooper’s liga­-ments), which contribute to the general support and shape of the breast (Figure 1.6).

Figure 1.6 As Scarpa’s fascia extends up onto the chest wall, it splits to envelope the breast, creating an anterior and posterior lamella. Supporting intraparenchymal fibers (Cooper’s ligaments) traverse the breast, lending structural support to the surrounding fat and parenchyma.

While the interdigitating fascial network is diffusely distributed, there is a well-documented and distinct fascial septum that is oriented horizontally across the breast at approximately the level of the 5th rib. This septum roughly separates the breast into a superior two-thirds and an inferior one-third. The septum takes origin from the pectoral fascia and is associated with a well-defined vascular arcade which extends with the septum up to the NAC. On the cranial side of this septum lies a vascular network which takes origin from perforating branches of the thoracoacromial artery and a branch of the lateral thoracic artery. On the caudal side are perforating branches from the intercostal arteries. The varied and diffuse nerve supply to the breast also courses, at least partly, within this septum. As such, this fascial condensation forms a connective tissue mesentery along which passes an important source of neurovascular support to the breast and, in particular, the NAC (Figure 1.7). This septum was first described as an independent entity by Wuringer and colleagues and, in my view, their contribution remains as one of the most important tools yet described to allow meaningful understanding of the intraparenchymal vascular and structural anatomy of the breast. This septum is so distinct that Wuringer has been able to describe a breast reduction technique that bases the blood supply to the NAC on this intraparenchymal vascular mesentery. Although uniformly present in breasts with any degree of hypertrophy, the septum and its associated mesentery tend to be more distinct in thinner patients who exhibit more of a fibrous nature to their breast (Figure 1.8). In breasts with a greater fat content, and particularly in the obese, the septum becomes less readily identifiable. However, the principles of pedicle management that the presence of this septum mandates do not change, no matter how distinct it is. For instance, when using an inferior pedicle technique to preserve the blood supply to the NAC, it becomes quite counterproductive to undermine the pedicle to such an extent that the caudal vascular sheet coming up into the pedicle becomes disrupted. The blood supply to the NAC at that point becomes based on dermal collateral flow, which can be less vigorous than the direct axial flow provided by the intercostal perforators running within the septal mesentery. Of course, as the length of the pedicle increases in larger breast reductions, preserving this vascular arcade becomes more critical in ensuring a viable NAC postoperatively. Although subtle, once I personally became aware of this anatomic relationship, I was able to locate it and respect the vascular pattern contained within the mesentery in every patient. It is interesting to postulate what effect inadvertent division of this breast septum may have had on previously reported instances of NAC ischemia after inferior pedicle breast reduction.

Figure 1.7 (A,B) A horizontally oriented fascial condensation within the breast takes origin from the pectoralis fascia at the level of the fifth rib and divides the breast into a superior two-thirds and an inferior one-third. Along this septum runs a neurovascular arcade, along both the cranial and caudal sides, creating a neurovascular mesentery within the breast. This septum provides a very important source of blood supply to the nipple–areola complex (NAC) and preserving these attachments can greatly diminish the potential for vascular compromise when performing pedicled breast procedures.

Figure 1.8 (A) Intraoperative appearance of patient undergoing an inferior pedicle breast reduction. The pedicle has been dissected free from the surrounding flaps and the superior, medial and lateral portions of the pedicle have been debrided to accomplish the reduction. (B) As the superior portion of the pedicle is lifted up, the breast septum can be visualized. The caudal septum remains intact and several large perforators can be seen running along the mesentery. The deep origin of the cephalad portion of the septum has been cut, which allows the superior end of the inferior pedicle to rotate away from the chest wall. (C) The inferior portion of the inferior pedicle has been bluntly separated away from the caudal portion of the septum, allowing full visualization of the entire septal mesentery. Several perforating vessels can be seen running in the septum. Any inferior pedicle technique should optimally preserve this vascular and connective tissue support and excessive undermining of the pedicle is best avoided to ensure adequate vascular inflow to the tissues of the inferior pedicle and the nipple–areola complex (NAC).

Understanding and identifying the subtle anatomical relationships noted at the level of the inframammary fold between the breast, Scarpa’s fascia and the anterior and posterior lamellae is of infinite importance in successful aesthetic breast surgery as a stable and properly positioned inframammary fold is the foundation upon which all other breast manipulations are based. For this reason, it is important to manipulate this anatomy to optimal advantage. The superficial fat of the anterior abdominal wall is divided into two distinct fatty layers. The superficial layer of fat is thicker, dense and more compact than the thinner and more areolar deeper layer. These two fatty layers are separated by a well-defined fascial condensation called Scarpa’s fascia (Figure 1.9). Along the inferior pole of the breast, Scarpa’s fascia inserts into the lamellar framework of the breast where the anterior and posterior lamellae fuse. As the enlarging breast develops, the mass effect of the tissue located just superior to this fusion point folds over itself inferiorly to passively form the inframammary fold (Figure 1.10 A,B). When incisions are made in the inframammary fold during breast augmentation, there is a tendency to incise through Scarpa’s fascia thus exposing the two fatty layers to forces from above in the form of the implant. Because the deep layer of fat is areolar and easily stretches open under the influence of any kind of force, any operative technique that opens this layer surgically can have the ultimate effect of inadvertently lowering the fold to a point lower than was initially planned as the weight of the overlying implant forces the loose subscarpal space open over time. In essence, abdominal skin below the planned incision is incorporated into the new breast skin envelope. This unplanned expansion of the lower pole of the breast and the resulting inferior implant malposition can have a decidedly negative impact on the shape of the resulting breast (Figures 1.11, 1.12 A,B). Alternatively, accessing the underside of the breast on top of Scarpa’s fascia protects the subscarpal space from potentially deforming pressure from above and, instead, any forces exerted by either implants or parenchyma are realized by the firmer and more compact superficial layer of fat, which is much less likely to give way. In this fashion, the location of the inframammary fold can be surgically positioned with greater confidence (Figures 1.13, 1.14 A,B). Incision strategies and fold management will be discussed in greater detail in subsequent chapters.

Figure 1.9 The fatty layer of the anterior abdominal and chest wall is divided into two layers by a dense fascial condensation called Scarpa’s fascia. The superficial fatty layer is thicker and more compact than the thinner and more areolar deeper layer.

Figure 1.10 (A) In the immature breast, Scarpa’s fascia ramifies into the inferior border of the breast and becomes confluent with the anterior and posterior connective tissue lamellae. (B) As the breast develops, the mass effect of the breast folds over the inferior parenchymal edge, passively creating the inframammary fold.

Figure 1.11 (A,B) Schematic diagram of a subglandular breast augmentation where the inframammary fold incision is made and the superficial layer of fat as well as Scarpa’s fascia is divided to expose the underside of the breast and create a pocket for the implant. As a result, the loose and areolar subscarpal space becomes the load-bearing area for the implant (pink area). Over time, this space gives way and opens up under the force of the overlying implant, resulting in inferior implant migration, incorporation of abdominal skin into the lower portion of the breast skin envelope and lowering of the location of the inframammary fold. One hallmark of this phenomenon is an inframammary scar that ‘rides up’ onto the breast and is not located in the fold itself. If this lowering of the fold was not planned as part of the surgical strategy, implant malposition and a less than desirable surgical outcome can be the result.

Figure 1.12 (A,B) Appearance of a patient after breast augmentation with loss of the inframammary fold in association with inferior implant malposition. Note that the incision has migrated up onto the lower breast as abdominal wall skin has been recruited to become part of the breast skin envelope.

Figure 1.13 (A,B) Schematic diagram of a subglandular breast augmentation where the inframammary fold incision is made, and Scarpa’s fascia is preserved. Dissection proceeds on top of Scarpa’s fascia until the underside of the breast is reached, where the pocket is then developed. In this fashion, the loose subscarpal space is never opened up and the firmer and more dense superficial layer of fat becomes the load-bearing tissue for the implant (pink area). This tissue is better able to withstand the force applied to it by the overlying implant and is resistant to stretch. In this way, the implant remains properly positioned and the fold is not lowered. As a consequence, the resulting inframammary fold scar stays in the fold and does not ride up onto the breast.

Figure 1.14 (A,B) Appearance of a patient after subglandular breast augmentation with preservation of the fold as described. Note that the implant remains properly positioned and, as a result, the scar remains directly in the fold.

The breast parenchyma and associated fat make up the bulk of the volume of the breast. The proportion that each contributes to this volume is subject to tremendous variability, not only between patients but also within the same patient, depending on any of the many variables which can effect the breast including age, weight, pregnancy, hormonal changes and genetics. Breasts that are particularly fibrous can be more difficult to sculpt surgically than predominantly fatty breasts. Also, not all fat is the same, as some patients have a blocky, firm consistency to their fat while others have a very loose and elastic texture to the fat. Preoperatively predicting what type of fat a patient has may impact what types of surgical maneuvers may be required to shape the breast appropriately, particularly in cases of mastopexy and reduction. For instance, patients with a firm, blocky fat will require greater precision in flap and pedicle development as their tissue will not mold together and conform as easily as a patient who has a looser and more elastic type of fat. Conversely, a patient with firmer fat may not need internal shaping sutures while the patient with a more elastic fatty consistency will often require internal parenchymal support to achieve the optimal result.

The skin of the breast can play a vital role in the outcome of any aesthetic breast procedure. As with other structures within the breast, the character of the skin of the breast can vary dramatically from patient to patient. In youth, the skin of the breast often has a compact consistency, exhibits excellent rebound when stress is applied to it and, generally, provides firm support to the underlying parenchyma and fat, which contributes greatly to the uplifted appearance of the youthful breast. Then, as a result of many influences including genetic factors, advancing age, weight gain and pregnancy, the dynamics of the skin of the breast change. As the underlying breast enlarges, the overlying skin becomes thinned particularly around the NAC, loses its ability to rebound and cannot support the volume of the breast as before. With increasing size, stretch marks can develop and the breast becomes variably ptotic with loss of shape. Either due to an inferior location initially or due to fluctuations in the filling out of the skin envelope, the location of the NAC can appear low in relation to the breast mound. Perhaps more importantly, after surgical alteration of the breast, the tendency for the breast skin to stretch seems to increase in many patients. This observation is easy to understand in light of the fact that during many aesthetic breast procedures the internal support structure of the breast is variably released. When this is coupled with any procedure which increases the volume of the breast, as in breast augmentation, it is understandable that the breast skin could stretch. Properly assessing the quality of the breast skin as well as the surface area of the skin envelope in relation to the underlying volume becomes quite important when designing a surgical strategy to iprove the aesthetics of the breast. Accurately judging how the skin will react to an underlying force such as a breast implant or repositioned breast parenchyma can greatly impact the long-term aesthetic result. Generally speaking, any aesthetic procedure which places undue reliance on the skin envelope of the breast to provide shape will eventually fail. It is far more reliable to provide a stable inner breast support structure and then allow the skin to simply redrape around the surgically created mound.

From an aesthetic standpoint, the muscles of the chest wall are important in breast surgery for two reasons. First, perforators from the main feeding vessels of the chest wall travel through the muscles to supply the breast. Therefore, for instance, the pectoralis major serves as a conduit for many perforators to enter the breast from the thoracoacromial system. Secondly and perhaps more importantly, breast implants are commonly placed under these chest wall muscles. Therefore, the location of these muscles in relation to the overlying breast becomes very important in determining the shape of the surgically altered breast (Figure 1.15). Although several chest wall muscles support the upper torso, the muscle which impacts most directly on the breast is the pectoralis major. This muscle takes origin from a wide attachment along the inner sternal area and this origin extends from the medial clavicle, down along the entire lateral sternal border and then variably onto the lower medial cartilages of ribs 6 and 7. Occasionally, the origin can extend down to the rectus abdominus fascia and the upper fibers of the external oblique muscle. Additionally, there are accessory fibers of origin which extend from the underside of the muscle and connect to the anterior bony surfaces of ribs 4 through 6. Vascular perforators from the intercostal system often accompany these accessory muscle origins. As a result, a wide area of origin for the pectoralis major is present and this area can cover as much as the medial fourth of the overlying breast contour. Recognizing this wide area of origin is very important when making a subpectoral pocket for breast augmentation and this anatomy will be discussed further in subsequent chapters. From this wide area of origin, the fibers converge into a thick tendon which inserts in a spiral fashion into the intertubercular groove of the humerus.

Figure 1.15 Muscles of the chest wall.

The blood supply to the pectoralis major muscle is diffuse, with the most direct named vessel being the thoracoacromial artery, although other branches enter the muscle via perforators from the internal mammary artery and anterior and lateral perforators from the intercostal arteries. Nerve supply to the pectoralis major comes from the medial and lateral pectoral nerves, which are named for the cord of origin in the brachial plexus rather than the anatomic location of the branches. The medial pectoral nerve courses through the pectoralis minor muscle to innervate the lateral and lower fibers of the pectoralis major muscle. This nerve is commonly encountered during the creation of a subpectoral breast pocket as it is typically seen running from the pectoralis minor up into the pectoralis major. The lateral pectoral nerve courses medial to the pectoralis minor muscle and enters the underside of the pectoralis major to provide innervation for the upper and medial portion of the muscle.