1 Preliminary Remarks about the Region

10.1055/b-0035-121993

1 Preliminary Remarks about the Region

The primary function of the female breast or mammary gland is nourishment of the newborn infant. The breasts are a symbol of femininity and are especially important in a woman’s self-image. This should be reflected in the diagnosis and treatment of breast disease and in reconstructive and corrective surgery. Breast cancer is the most common malignant disease in women.

1.1 Topography of Chest Wall, Axilla, and Back

1.1.1 Chest Wall

The breast lies on the chest wall with which it is intimately related with regard to blood supply, lymphatic drainage, and innervation. The breast develops embryologically from the skin. Anatomists and surgeons dispute whether the superficial body fascia can be divided into a superficial (Camper fascia) and a deep layer (Scarpa fascia), which explains the often inconsistent terminology. Doubt has been cast on the hypothesis that the mammary gland is located between the superficial and deep layers of the superficial fascia. What is certain is that the suspensory ligaments of the breast (ligaments of Cooper) pass through the parenchyma of the breast, radiating from the superficial fascia on the pectoralis muscle to the skin and helping to give the breasts their shape.

Mammary Glands

Mammary gland. The mammary gland consists of 16 to 20 distinct lobes. Each of these lobes has its own lactiferous duct opening into the nipple. These lactiferous ducts are divided into the excretory duct, directly behind the nipple, and the lactiferous sinus, a dilatation of the duct approximately 1 cm beneath its opening. The lactiferous ducts are a continuation of the lactiferous sinuses and branch extensively as they pass to the lobules, which are the site of actual milk production.

Montgomery glands. The areolar (Montgomery) glands, 10 to 15 in number, are located in a circle around the nipple and may be apparent as small elevations. Their secretion assists lactation.

Classification of pathological changes. Most (pathological) duct ectasia develops in the lactiferous sinuses. Invasive ductal breast cancer imitates the histological picture of the lactiferous ducts, while the typical histological acinar appearance of the lobules is seen in invasive lobular breast cancer.

Muscle Layers

Most of the breast is situated on the pectoralis major muscle, which in turn lies directly on the actual chest wall, consisting of the ribs and intercostal muscles. The origin of the serratus anterior muscle, which runs posterolaterally, is beneath the diagonal inferior border of the pectoralis major between the axilla and the inferior part of the sternum. The pectoralis minor, with its origin on the scapula, radiates toward the anterior chest wall directly behind the pectoralis major. Other muscles that may be involved in breast surgery include the most cranial part of the rectus abdominis muscle, which is attached medially to the sternum and distal ribs, and the external oblique muscle of the abdomen, which is located together with the serratus anterior in the inferolateral part of the thorax.

Table 1.1 Muscles of the chest wall and back–origins, insertions, function, and innervation
Name	Origin	Insertion	Function	Innervation
Pectoralis major m.	Sternal half of clavicle, anterior surface of sternum, cartilage of ribs 2–6 and rectus sheath	Crest of greater tubercle of humerus	Adduction of arm, lowering of raised arm	Medial and lateral pectoral nerves from the brachial plexus
Pectoralis minor m.	Ribs 2–5 near the costochondral junction	Coracoid process of scapula	Depression of shoulder girdle	Medial and lateral pectoral nerves from the brachial plexus
Intercostal mm.	Upper border of rib	Lower border of rib	Respiratory muscles (expiration)	Intercostal nerves
Serratus anterior m.	Ribs 1–9	Scapula: superior angle, medial border, inferior angle	Fixes scapula to the trunk, assists arm elevation	Long thoracic nerve from the brachial plexus
Latissimus dorsi m.	Spinous processes of lower thoracic vertebrae, lumbar vertebrae, posterior surface of sacrum, outer lip of iliac crest, accessory slips from the inferior ribs and scapular slip from the inferior angle of the scapula	Crest of lesser tubercle of humerus, together with teres major m.	Depression of elevated arm, internal rotation, adduction in shoulder joint	Thoracodorsal nerve from the brachial plexus
Rectus abdominis m.	Outer surface of costal cartilages 5–7 and xiphoid	Indirectly to the pubis/symphysis	Flexes trunk, elevates pelvis, abdominal pressure	Middle and inferior intercostal nerves
External oblique muscle of abdomen	Outer surface of ribs 5/6–12	Outer lip of iliac crest, inguinal ligament, anterior layer of rectus sheath	Flexes trunk, elevates pelvis, increases abdominal pressure. Unilateral function: rotation of thorax	Iliohypogastric nerve, ilioinguinal nerve, inferior intercostal nerves

Blood Supply

From the medial side, the mammary gland is supplied by perforating branches of the internal mammary artery. From the axillary and cranial direction, the blood supply is mainly through the lateral thoracic artery, which runs on the serratus anterior beneath the pectoralis minor. The lateral blood supply comes from branches of the intercostal arteries. Sooner or later, the different arteries drain into a subcutaneous vascular plexus, which is very important in supplying the skin, areola, and nipple, and must be protected during many oncoplastic surgical procedures. Perforators from the pectoralis major enter the breast directly. Understanding the external and internal blood supply and course of the blood vessels of the breast is important especially for oncoplastic pedicle techniques (Chapter 3.3.2) and during dissection of the skin layer.

Lymphatic Drainage

The lymphatic drainage of the breast essentially follows the arteriovenous vessels. The medial third of the breast drains especially to retrosternal lymph nodes. Smaller lymphatic pathways in the superior part of the breast can drain directly into the subclavian lymph nodes, partly through the Rotter (interpectoral) lymph nodes (level II). Most of the breast drains through the classic sentinel node group at the border of the pectoralis muscle into the level I axillary lymph nodes. Lymphatic vessels crossing the sternum to the contralateral side have also been described.

Innervation

The breast receives sensory innervation via a number of nerve pathways. The skin of the superior part of the breast is innervated by terminal branches of the supraclavicular nerves, while the remainder of the skin is innervated by lateral and medial branches of the intercostal nerves. Denervation problems in the chest wall are very rare; they are more frequent in the skin of the medial upper arm after the division (sometimes unavoidable) of the intercostobrachial nerves, which pass through the axilla to the upper arm.

**Fig. 1-1** Most of the glandular tissue of the breast lies on the pectoralis major muscle, the lateral border of which is roughly at the level of the nipple–areola complex.

**Fig. 1-2** Typical distribution of lymphatic drainage pathways and regional lymph nodes: 1 = scapular lymph nodes (LNs), 2 = central LN, 3 = external mammary LN, 4 = infraclavicular LN, 5 = axillary vein LN, 6 = interpectoral LN, 7 = internal mammary LN.

**Fig. 1-3** Division of axillary lymph nodes into levels I–III; the pectoralis minor muscle is the anatomical landmark. Level I lymph nodes are lateral and inferior to the pectoralis minor, level II defines the lymph nodes located posteriorly between the lateral and medial borders of the pectoralis minor, and level III describes the lymph nodes medial to the pectoralis minor.

**Fig. 1-4** Lateral section of the intramammary blood supply. Besides the deep perforators from the pectoralis major, an important subcutaneous vascular plexus is supplied from the periphery at the base of the breast by terminal branches of the internal mammary artery and lateral thoracic artery. The concept of a “central” pedicle with dissection of the overlying skin is apparent.

**Fig. 1-5** The subcutaneous, subdermal arteriovenous plexus is highly important for supplying the skin and also the neighboring nipple–areola complex. This vascular plexus should be protected during mastectomy, with dissection in the largely avascular plane between mammary gland and subcutaneous fat, which is not always easy. The thickness of this layer varies according to the patient’s weight and physique.

1.1.2 Axilla

The axilla is a virtual space. Its anatomical boundaries are defined as follows. Medially, the axilla is bounded by the pectoralis major and pectoralis minor muscles and the bony thorax (ribs). For anatomists, the posterior boundary is formed by the subscapularis and teres major muscles. The latissimus dorsi muscle defines the lateral boundary. The superior boundary is described (anatomically) as consisting of the outer surface of the first rib, the underside of the clavicle, and the upper border of the scapula, which basically corresponds to the shoulder joint. The inferior boundary is considered to be the collateral artery from the thoracodorsal trunk to the serratus anterior.

1.1.3 Back

The anatomy of the back is important for the breast surgeon when the latissimus dorsi muscle is dissected for autologous breast reconstruction. Although no major vessels run posteriorly, there are numerous perforating vascular connections between the different muscles, which can retract into muscle, rendering hemostasis difficult.

**Fig. 1-6** For the breast surgeon, the lateral border of the pectoralis major is the landmark for the axilla. The superficial subcutaneous fascia must often be opened to allow blunt dissection of the important neurovascular bundles. The axillary vein forms the highest point of axillary dissection. The thoracodorsal neurovascular structures including the thoracodorsal nerve, which pass (via the subscapular artery and vein) in a posterolateral direction into the latissimus dorsi, are exposed. Finally, the long thoracic nerve, which runs on the chest wall, is identified in the same plane. This ensures that level I lymph node dissection can be performed safely. For level II dissection, the pectoralis minor is identified beneath the pectoralis major and dissection proceeds along the vein posterior to the muscle in a superomedial direction.

**Fig. 1-7** During (complete or partial) mobilization, the latissimus dorsi must be divided medially from the spinous processes of the lower thoracic vertebrae and lumbar vertebrae. The muscle is directly beside the trapezius muscle, especially in its superomedial part. This area is highly vascular, and isolation and targeted coagulation of vessels is preferable to accidental division with retraction. The muscle must also be divided from the back of the sacrum and from its aponeurotic origin on the external lip of the iliac crest. Accessory muscle slips to the inferior ribs and sometimes to the inferior angle of the scapula are often found and require sharp dissection.

**Fig. 1-8** The latissimus dorsi is inserted on the crest of the lesser tubercle of the humerus by a tendon that surrounds the teres major muscle. Division of this insertion allows great flexibility when the muscle is used for volume replacement, for either total or partial breast reconstruction during extended breast-conserving surgery. When mobilizing it toward the humerus, the thoracodorsal neurovascular bundle and thoracodorsal nerve must be protected.

1.2 Breast Cancer

1.2.1 Fundamentals for the Surgeon

Epidemiology. Breast cancer is the most common malignant disease in women. Despite the good 5- and 10-year cure rates of up to 80% it heads the mortality statistics, ahead of colon and lung cancer. The lifetime risk of developing the disease is 7 to 9% with life expectancy of 80 years. This frequently published figure is often misunderstood. Starting from the maximum risk, this means that the risk of developing the disease becomes smaller with each year lived without breast cancer. The peak age is between 50 and 70 years. The incidence of breast cancer is increasing whereas mortality is unchanged or decreasing. Nearly one-third of all breast cancers are now smaller than 1 cm, not least as a result of extensive mammographic screening, so a large percentage of them are curable.

Risk factors. The classic risk factors are increasing age, a history of cancer in the contralateral breast, and a positive family history of premenopausal disease in a first-degree relative, when the individual risk rises to up to 30%. Nevertheless, most breast cancers are sporadic. According to current knowledge, only about 5 to 10% have a direct hereditary genetic cause, that is, mutations in the BRCA1 and BRCA2 genes. Another risk factor that may be important in screening for risk stratification in the future is the postmenopausal “dense” breast (ACR 3/4). Pregnancy and having the first child at a young age are protective factors, while breast-feeding does not influence the incidence of breast cancer. The question of the influence of oral contraceptives and oral hormone replacement therapy is particularly problematic; oral contraceptives appear to increase the incidence minimally and this effect was no longer seen 10 years after stopping the medication. The situation with hormone replacement is even harder to assess: while nonhysterectomized patients on estrogen and progesterone hormone replacement had an increased risk for breast cancer, this was not observed in hysterectomized women taking estrogen-only hormone replacement. With the negligible shifts in risk, each patient must be considered individually.

Histological types and treatment. The histological classification into invasive ductal breast cancer, the incidence of which is reported as 60 to 65% of all breast malignancies, and invasive lobular carcinoma, which accounts for about 15 to 20% of the tumors, is important for the surgeon. Medullary carcinoma (about 5% of cases), mucinous carcinoma (< 5%) and tubular carcinoma (< 1%) are much rarer. Premalignant lesions, collectively known as ductal intraepithelial neoplasia and lobular intraepithelial neoplasia (DIN, LIN), are as important as the histology of invasive carcinoma. Originally, the only defined pathological condition was ductal carcinoma in situ (DCIS), which was graded G1 to G3 depending on the degree of differentiation. It soon became clear that this is a precancer, as subsequent carcinoma rates were up to 50%. Over time it was realized that other precursor lesions could be distinguished and different nomenclature systems (DIN, WHO, DCIS) were introduced to describe the entire spectrum of ductal hyperplasia. Parallel use of these nomenclatures has led to a certain degree of confusion. Tables 1.2 to 1.4 show the nomenclatures and treatment options.

Based on data obtained in studies, nearly every larger DCIS now receives radiotherapy after breast-conserving resection. Radiotherapy can be omitted by agreement with the patient if the historically important Van Nuys prognostic index is ≤ 4, that is, if the lesion is small (< 2 cm), R0 resection is adequate (> 5–10 mm), and grading is favorable (low or medium grade). If DCIS recurs locally, simple mastectomy should be considered. Around 50% of DCIS recurrences are invasive carcinomas. DCIS with focal microinvasion is treated like an invasive ductal breast cancer.

While high-grade DIN is regarded today as precancer, the majority of lobular neoplasias (LINs) are considered to be risk markers. Lobular neoplasia is often multifocal (40–80%) and bilateral (30–70%). Ipsilateral and contralateral carcinomas occur in between 10 and 20% of patients over a period of 10 to 20 years. LIN3 is often called LCIS (lobular carcinoma in situ). The recommended treatment for LCIS (synonym: pleomorphic LIN) and DCIS is similar.

If lobular neoplasia is diagnosed on needle biopsy, open biopsy of the area in question is advisable above LIN2–3 because higher-grade preinvasive or invasive lesions are often found. If LIN1–2 is diagnosed in an excision biopsy, no further treatment is indicated regardless of resection status (R0, R1). By contrast, a LIN3/LCIS lesion should be completely resected, like DCIS. Further resection is not performed if LIN1–2 is found at the resection margin in breast-conserving surgery, but is required if an LIN3 lesion is found. Postoperative radiation after LIN/LCIS resection does not appear justified according to current knowledge.

Table 1.2 DCIS.DIN nomenclature
DIN nomenclature	WHO nomenclature	DCIS nomenclature	Treatment options
DIN1a	Flat epithelial hyperplasia		Excision, especially to exclude higher-grade associated lesions. Marginal abnormalities do not require further resection
DIN1b	Atypical ductal hyperplasia
DIN1c	Ductal carcinoma in situ (DCIS)	DCIS grade 1	Resection according to oncological criteria as with invasive disease. Safety margin pR0 > 0.5–1 cm. Postoperative radiation with breast conservation. Consider sentinel lymph node excision if tumor size > 4 cm
DIN2		DCIS grade 2
DIN3		DCIS grade 3

Table 1.3 Van Nuys prognostic index for ductal carcinoma in situ (DCIS)
Score	1	2	3
Histological grade	Low grade, no necrosis	Low grade with necrosis	High grade
Size (mm)	1–15	16–40	> 40
Distance from tumor-free resection margin (mm)	> 10	1–9	<1
Age (years)	> 60	40–60	< 40
Group 1: Prognostic index 4–6, low risk: no treatment Group 2: Prognostic index 7–9, medium risk: radiotherapy Group 3: Prognostic index 10–12, high risk: mastectomy

Table 1.4 Treatment recommendations for lobular neoplasia
Lobular neoplasia	Treatment option
LIN1	No additional investigation if breast otherwise normal (imaging negative). In excision biopsies, the R status is unimportant
LIN2	At least open biopsy to exclude associated higher-grade lesions. No further resection required with LIN2 at resection margin
LIN3 = LCIS	Treatment as for DCIS

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1 Preliminary Remarks about the Region