Overview

The breast is an appendage of skin and is a modified sweat gland. It is composed of glandular tissue, fibrous or supporting tissue, and fat. The functional unit of the breast is the terminal duct lobular unit, and any secretions produced in the terminal duct lobular unit drain towards the nipple into 12–15 major subareolar ducts. Although often described as being segmental, the glandular and ductal structures of the breast interweave to form a composite mass. In the resting state, the terminal duct lobular unit secretes watery fluid that is reabsorbed as it passes through the ductules and ducts. This rarely reaches the surface of the nipple because the nipple ducts are blocked or plugged by keratin. If the keratin becomes dislodged, then this physiological secretion can be seen on the surface of the nipple. It varies in colour from white to yellow to green to blue/black, and can be produced in up to two-thirds of non-pregnant women by gentle cleaning of the nipple and massage of the breast.

Anatomy

The breast lies between the skin and the pectoral fascia, to which it is loosely attached. It extends from the clavicle superiorly down on to the abdominal wall, where it extends over the rectus abdominis, external oblique and serratus anterior muscles. The axillary tail of the breast runs between the pectoral muscles and latissimus dorsi to blend with the axillary fat. The breast is supplied by the lateral thoracic artery or the lateral thoracic branch of the axillary artery superolaterally, and by perforating branches of the internal mammary artery superomedially. The functioning unit of the breast, the terminal duct lobular unit, is lined, as are the draining ducts, by a single layer of columnar epithelial cells surrounded by myoepithelial cells. The major subareolar ducts in their terminal portion are lined by stratified squamous epithelium.

The main route of lymphatic spread of breast cancer is to the axillary nodes, which are situated below the axillary vein. On average, there are 20 nodes in the axilla below the axillary vein (Fig. 19.1). These are separated into three levels by their relation to the pectoralis minor muscle. Nodes lateral to the pectoralis minor are considered level I, those beneath are classified as level II, and the nodes medial to pectoralis minor are level III. Level I nodes, which are nearest the breast, are usually affected first by breast cancer. In less than 5% of patients, levels II or III nodes are involved without level I nodes being affected. Lymph also drains to the internal mammary nodes. Occasionally, the main route of lymph drainage of a cancer is to the interpectoral nodes situated between the pectoralis major and minor muscles.

Fig. 19.1 Lymph node drainage of the breast.

Congenital abnormalities

These are most commonly the result of persistent extra-mammary portions of the breast ridge. In the sixth week of embryonal development, a bilateral ridge called the ‘milk line’ develops and extends from the axilla to the groin. Segments coalesce into nests of cells and, in humans, all but one of these nests opposite the fifth intercostal space disappear. In 1–5% of people, one or more of the other nests persists as supernumerary or accessory nipples or, less frequently, as breasts. The most common site for an accessory nipple is in the milk line between the normal breast and the umbilicus; the most common site for an accessory breast is the lower axilla. Supernumerary nipples or breasts rarely require treatment unless they are unsightly. Accessory breast tissue is subject to the same diseases found in normally placed breasts.

Some degree of breast asymmetry is normal, the left usually being the larger of the two. One breast can be absent or hypoplastic, and this is often associated with pectoral muscle defects. Some patients have abnormalities of the pectoralis muscle and absence or hypoplasia of the breast, associated with a characteristic deformity of the upper limb; this cluster of anomalies is called Poland’s syndrome. Abnormalities of the chest wall, such as pectus excavatum and scoliosis of the thoracic spine, can make normal breasts look asymmetric. True asymmetry can be treated by augmentation of the smaller breast, reduction or elevation of the larger breast, or a combination of the two.

Hormonal control of breast development and function

Enlargement of the breast bud in the first week or two of life occurs in approximately 60% of newborn babies; the gland may reach several centimetres in size before regressing. This is because circulating maternal oestrogens cause one or both breasts to enlarge and secrete a colostrum-like fluid (witch’s milk) from the nipple. The swelling usually subsides within a few weeks and the breasts then normally remain dormant until puberty, when the onset of cyclical hormonal activity stimulates growth.

The life cycle of the breast consists of three main periods: development (and early reproductive life), mature reproductive life and involution. Development occurs at puberty and involves proliferation of ducts and ductules associated with very rudimentary lobule formation. The breast then undergoes regular changes in relation to the menstrual cycle. During pregnancy, the breast approximately doubles in weight, and lobules and ducts proliferate in preparation for milk production. Lobular development only becomes marked during pregnancy. Milk production during pregnancy is inhibited by ovarian and placental steroids. Delivery reduces the amount of circulating oestrogen and increases the sensitivity of the breast epithelium to prolactin. Suckling stimulates the release of prolactin and oxytocin, with oxytocin stimulating the myoepithelial cells to eject milk into the terminal ducts. By the age of 30, ageing or involution is evident and continues to the menopause and beyond. During involution, glandular tissue and fibrous tissue atrophy and the shape of the breasts changes and they become more ptotic or droopy. Microscopic changes in the glandular tissue that occur during involution include fibrosis, the formation of small cysts (microcysts) and a focal increase in the number of glandular elements (adenosis). These changes were previously considered abnormal and were called fibrocystic disease or fibroadenosis. However, they occur as part of normal breast ageing or involution and should not be considered as disease.

Clinical features

Approximately 25% of all surgical referrals relate to breast problems. In the UK, 1 in 4 women will attend a breast clinic, and 1 in 9 will develop breast cancer at some point in their lives. The most common symptoms are a breast lump, which may or may not be painful; an area of lumpiness; pain alone; nipple discharge; nipple retraction; a strong family history of breast cancer; breast distortion; swelling or inflammation; or a scaling nipple or eczema. The most important pointer to the diagnosis is the age of the patient. Although malignant disease can occur in young women, benign conditions are much more common. The duration of any symptom is important; breast cancers usually grow slowly, but cysts may appear overnight. Details of risk factors, including family history and current medication, should be obtained and recorded.

Clinical examination

The patient is asked to undress to the waist and sit facing the examiner. Inspection should take place in good light with the patient’s arms by her side, above her head, and then pressing on her hips (Fig. 19.2). Skin dimpling or a change of contour is present in a high percentage of patients with breast cancer (Fig. 19.3). Breast palpation is performed with the patient lying flat with her arms above or under her head. All the breast tissue is examined, using the fingertips to detect any abnormality (Fig. 19.4). Any abnormal area is then examined in more detail, to determine the texture and outline of the mass. Deep fixation is assessed by asking the patient to tense the pectoralis major muscle; this is accomplished by asking her to press her hands on her hips. All palpable lesions should be measured with callipers and the size and site (using the clock) recorded in the hospital notes.

Fig. 19.2 Clinical inspection of the breast.

Fig. 19.3 Skin dimpling in the lower inner quadrant of the left breast associated with breast cancer.

Fig. 19.4 Clinical examination of the breast.

If the patient complains of nipple discharge, an attempt should be made to reproduce the discharge and to determine whether it arises from a single or multiple ducts. Any discharge should be tested for haemoglobin. Only marked or moderate amounts of haemoglobin in a nipple discharge are significant.

Assessment of regional nodes

Once the breast has been palpated, the nodal areas are checked (Fig. 19.5). Clinical assessment of axillary nodes is not always accurate. Palpable nodes can be identified in up to 30% of patients with no clinically significant breast disease, while up to 25% of patients with breast cancer who have no palpable nodes on examination will be found histologically to have metastatic disease in the axillary nodes. Ultrasound is better at assessing axillary nodes than clinical examination. The supraclavicular nodes are best examined from behind.

Fig. 19.5 Examination of the regional nodes.

Imaging

Ultrasonography

High-frequency waves are beamed through the breast and reflections are detected and turned into images. Cysts show up as transparent objects (Fig. 19.6) and other benign lesions tend to have well-demarcated edges (Fig. 19.7), whereas cancers usually have an indistinct outline and absorb sound, resulting in a posterior acoustic shadow (Fig. 19.8). Ultrasound is also used to assess axillary nodes in patients with breast cancer. Where nodes are enlarged or the cortex of the node thickened, fine needle aspiration cytology or core biopsy should be performed to establish whether nodal metastases are present.

Fig. 19.6 Ultrasound of a cyst.

Fig. 19.7 Ultrasound of a fibroadenoma.

Fig. 19.8 Ultrasound of a cancer.

Fine needle cytology and biopsy

Core biopsy

Several cores are removed from a mass or an area of microcalcification by means of a cutting needle technique after injection of local anaesthetic (Fig. 19.9). A 14-gauge needle combined with a mechanical gun produces satisfactory samples and allows the procedure to be performed single-handed. Core biopsy can be performed using palpation to guide biopsy but is most successful when image guidance is employed (ultrasound for mass lesions, stereotactic biopsy for calcifications which are usually impalpable). Vacuum-assisted core biopsy devices allow several large cores to be removed without withdrawing the needle from the breast, and have some advantages when biopsying areas of indeterminate microcalcification detected on screening.

Fig. 19.9 Core biopsy being performed.

One-stop clinics

The combination of clinical examination, imaging (mammography with or without ultrasonography for women over 35 years, and ultrasonography for women under 35 years) and core biopsy with or without cytology is known as triple assessment. Patients presenting with a breast lump or suspicious lesion on imaging should have triple assessment performed during a single clinic visit. This allows the majority of patients seen at a breast clinic who have normal breasts to be reassured and discharged after one visit.

Accuracy of investigations

False-positive results occur with all diagnostic techniques. The sensitivity of clinical examination and mammography varies with age, and only two-thirds of cancers in women under 50 years of age are considered suspicious or definitely malignant on clinical examination or mammography (Table 19.1). Image-guided core biopsy is the most accurate and efficient of the various techniques used to diagnose breast masses.

Table 19.1 Accuracy of investigations in the diagnosis of symptomatic breast disease in specialist clinics

Juvenile hypertrophy

Uncontrolled overgrowth of breast tissue occurs occasionally in adolescent girls, whose breast development initially begins normally at puberty and is followed by rapid breast growth. These changes are usually bilateral, but may be limited to one breast or part of one breast. This process is often referred to as virginal or juvenile hypertrophy (Fig. 19.10). However, it is not hypertrophy, as there is an increase in the amount of stromal tissue rather than in the number of lobules or ducts. This excessive growth is an aberration rather than a true disease, and presenting symptoms are large breasts and pain in the shoulders, neck and back or under the bra straps. Treatment is by reduction mammaplasty.

Fig. 19.10 Juvenile hypertrophy.

Fibroadenoma

Fibroadenomas are classified in most texts as benign tumours, but are best considered as aberrations of development rather than true neoplasms. The reasons are that fibroadenomas develop from a whole lobule rather than from a single cell, and show hormonal dependence similar to that of normal breast tissue, lactating during pregnancy and involuting in the perimenopausal period. Fibroadenomas are most commonly seen immediately following the period of breast development and growth in the 15–25-year age group (Fig. 19.11). They are usually well-circumscribed, firm, smooth, mobile lumps, and may be multiple or bilateral. Although a small number of fibroadenomas increase in size, most do not and over one-third become smaller or disappear within 2 years. Fibroadenomas have a characteristic appearance with easily visualized margins on ultrasound (Fig. 19.7). Large or giant fibroadenomas (> 5 cm) are infrequent but are more commonly seen in women from certain African countries. Occasionally, a fibroadenoma in an adolescent girl undergoes rapid growth, a condition called juvenile fibroadenoma (Fig. 19.12). Once a diagnosis of fibroadenoma has been established on core biopsy, options for management in lesions measuring less than 4 cm include reassurance with no follow up needed or excision; fibroadenomas over 4 cm in diameter should be excised to ensure that phyllodes tumours are not missed (see below). A carcinoma arising in a fibroadenoma is extremely rare. Patients with simple fibroadenomas are not at significantly increased risk of developing breast cancer.

Fig. 19.11 Percentage of patients in 10-year age groups with a discrete breast lump who have common benign conditions and breast cancer.

Fig. 19.12 Juvenile fibroadenoma.

Cyclical mastalgia

Most patients require no specific treatment. Evening primrose oil was previously used for breast pain but recent studies have failed to show any benefit and it is no longer used. Effective agents include danazol (100 mg/day) and tamoxifen (10 mg/day). Tamoxifen does not have a product licence for this condition but it improves pain in 80% of patients. Agnus castis, a fruit extract, has been shown in randomized studies to be somewhat effective in reducing breast pain.

Nodularity

Lumpiness and nodularity in the breast can be diffuse or focal. Diffuse nodularity is normal, particularly premenstrually. In the past, women with lumpy breasts were regarded as having fibroadenosis or fibrocystic disease, but this diffuse nodularity is not associated with any underlying pathological abnormality and so these terms are inappropriate. Focal nodularity is a common cause for women seeking medical advice and is seen in women of all ages (Fig. 19.11). Patients with benign focal nodularity often report that the lump fluctuates in size in relation to the menstrual cycle. Breast cancer should be excluded by imaging +/- core biopsy in women with persistent localized asymmetric areas of nodularity, as breast cancer in younger women often presents as nodularity rather than a discrete mass.

Non-cyclical breast pain

Localized pain in the chest wall is a common reason for patients to be referred for advice. The pain may appear to be in the breast but examining a patient on her side to move the breast away from the chest wall demonstrates that the ribs or chest wall muscle are the site of origin of the pain. Oral nonsteroidal anti-inflammatory agents (NSAIDs) are usually effective in improving chest-wall pain. Up to 60% of patients with a persistent localized painful area in the chest wall can be effectively treated by infiltration of local anaesthetic and steroid (2-5 ml 0.5% bupivacaine added to 40 mg of methylprednisolone).

Palpable breast cysts

Approximately 7% of women in developed countries develop a palpable breast cyst at some time in their life. Cysts constitute 15% of all discrete breast masses. They are distended, involuted lobules and are most frequently seen in the perimenopausal period (Fig. 19.11). Clinically, they are smooth discrete lumps that can be painful and are sometimes visible. Mammographically, they have characteristic haloes and are easily diagnosed by ultrasonography (see Fig. 19.6). Symptomatic palpable cysts are treated by aspiration and, provided the fluid is not blood-stained, it is discarded. Cysts that contain blood-stained fluid require excision to exclude an associated intracystic cancer. Such cancers are rare and are usually evident on ultrasound. Most cysts are asymptomatic and, following ultrasound assessment, do not need aspiration. All patients with cysts should have mammography, preferably before cyst aspiration, as between 1 and 3% will have a cancer, usually remote from the cyst, visible on mammography (Fig. 19.13). Patients with cysts have a slightly increased risk of developing breast cancer, but the magnitude of this risk is not considered of clinical significance.

Fig. 19.13 Mammogram of a cyst and a cancer.

Sclerosis

Areas of excessive fibrosis or sclerosis can occur as part of stromal involution. Sclerosing lesions include radial scars, complex sclerosing lesions and sclerosing adenosis and can produce stellate lesions or localized calcification that mimic breast cancer mammographically, and so can cause diagnostic problems during screening. Radial scars are difficult to differentiate on imaging from small cancers and sometimes have small areas of pre cancer (DCIS see page 312) down one of the legs of the scar so most are removed.

Duct ectasia

The major subareolar ducts dilate and shorten with age; when symptomatic, this is known as duct ectasia. By the age of 70, 40% of women have dilated ducts, some of whom present with nipple discharge or retraction. The discharge is usually cheesy and the retraction is classically slit-like (Fig. 19.14), which contrasts with breast cancer, in which the whole nipple is pulled in (Fig. 19.15). Surgery is indicated if the discharge is troublesome or if the patient wishes the nipple to be everted.

Fig. 19.14 Duct ectasia showing slit-like nipple retraction.

Fig. 19.15 Asymmetric nipple inversion in a patient with breast cancer.

Epithelial hyperplasia

An increase in the number of cells lining the terminal duct lobular unit is known as epithelial hyperplasia, the degree of which is graded as mild, moderate or florid. If the hyperplastic cells show cellular atypia, the condition is called atypical hyperplasia. Women with atypical hyperplasia have a significant increase in their risk of breast cancer. The absolute risk of developing breast cancer for a woman with atypical hyperplasia without a first-degree relative with breast cancer is 8% at 10 years; for women with a first-degree relative with breast cancer the risk is 20–25% at 15 years.

Duct papillomas

These can be single or multiple. They are very common, and should be considered as aberrations rather than true neoplasms as they show minimal malignant potential. They can cause persistent and troublesome nipple discharge, which can be either frankly blood-stained (Fig. 19.16), or serous. Treatment comprises removal of the discharging duct (microdochectomy), which removes the papilloma (if this is the cause) and allows exclusion of an underlying neoplasm, seen in approximately 5% of women who present with a blood-stained nipple discharge.

Fig. 19.16 Blood-stained nipple discharge.

Lipomas

These are soft, lobulated, radiolucent lesions and are common. Interest lies in their confusion with pseudolipoma (a soft mass that can be felt around a cancer, caused by indrawing of surrounding fat).

Phyllodes tumours

These rare fibro-epithelial neoplasms may be malignant in their behaviour, although most are benign. They present as localized discrete masses that clinically feel like fibroadenomas, although they tend to be larger (> 4 cm). Up to 20% of benign phyllodes tumours recur locally following simple excision. In more malignant lesions it is the sarcomatous element that recurs; approximately one-quarter of lesions reported as malignant metastasize. Treatment of phyllodes tumours, whether malignant or benign, is wide excision. If the lesion is large, mastectomy may be needed to ensure complete removal.

Other benign tumours that occur in the breast include granular cell tumours, neurofibromas and leiomyomas.

Lactating infection

Improvements in maternal and infant hygiene have reduced considerably the incidence of infection associated with breastfeeding. When infection does occur, it usually develops within the first 6 weeks of breastfeeding. Presenting features are pain, swelling, tenderness and a cracked nipple or skin abrasion. Staphylococcus aureus is the most common organism, although Staph. epidermidis and streptococci are occasionally implicated. Drainage of milk from the affected segment is reduced, with the resultant stagnant milk becoming infected. Early infection is treated with flucloxacillin or co-amoxiclav. An established abscess should be treated by recurrent aspiration, or by incision and drainage (Fig. 19.17). Women should be encouraged to breastfeed, as this promotes milk drainage from the affected segment. Rarely, milk flow needs to be stopped using cabergoline, a prolactin antagonist.

Fig. 19.17 Lactating breast abscess.

Non-lactating infection

This can be separated into infections that occur centrally in the periareolar region and those affecting the periphery of the breast.

Mammary duct fistula

This is a communication between the skin – usually at the areolar margin – and a major subareolar duct (Fig. 19.18). Treatment is by excision of the fistula and diseased duct(s) under antibiotic cover.

Fig. 19.18 Mammary duct fistula and periductal mastitis.

Peripheral non-lactating abscesses

These are less common than periareolar abscesses and are sometimes associated with an underlying condition, such as diabetes, rheumatoid arthritis, steroid treatment, granulomatous lobular mastitis or trauma. Infection associated with granulomatous lobular mastitis can be a particular problem, as there is a strong tendency for this condition to persist and recur despite surgery. Peripheral abscesses should be treated by recurrent aspiration with antibiotics (Table 19.3), or incision and drainage under local anaesthesia.

Summary Box 19.2 Breast infection

• Antibiotics should be given early to reduce abscess formation

• Hospital referral is indicated if infection does not settle rapidly on antibiotics

• If an abscess is suspected, this should be confirmed by ultrasound or aspiration

• If the lesion is solid on ultrasound or aspiration a core biopsy should be performed to exclude an underlying inflammatory carcinoma.

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