Breasts and Axillae

anatomy And Physiology

In this chapter, the terms “female,” “male,” “female breasts,” and “male breasts” are used in order to differentiate between the composition, development, and maturation of breast tissue in patients assigned as female or male at birth, respectively. This becomes important to the examination and health of patients who, for example, are transgender male or non-binary, but still have “female” breast tissue. Additionally, “female breasts” refer to persons with substantial breast tissue, as breast tissue changes may also occur as a result of hormonal or surgical intervention.

The breasts are paired mammary glands located on the anterior chest wall, superficial to the pectoralis major and serratus anterior muscles ( Fig. 17.1 ). In female breasts, the breast extends from the second or third rib to the sixth or seventh rib and from the sternal margin to the midaxillary line. The nipple is located centrally, surrounded by the areola. The male breast consists of a small nipple and areola overlying a thin layer of breast tissue.

The female breast is composed of glandular and fibrous tissue as well as subcutaneous and retromammary fat. The glandular tissue is arranged into 15 to 20 lobes per breast that radiate about the nipple. Each lobe is composed of 20 to 40 lobules, and each lobule consists of milk-producing acinar cells that empty into lactiferous ducts. These cells are small and inconspicuous in nonpregnant, nonlactating women. A lactiferous duct drains milk from each lobe onto the surface of the nipple.

The layer of subcutaneous fibrous tissue provides support for the breast. Suspensory ligaments (Cooper ligaments) extend from the connective tissue layer through the breast and attach to the underlying muscle fascia, providing further support. The muscles forming the floor of the breast are the pectoralis major, pectoralis minor, serratus anterior, latissimus dorsi, subscapularis, external oblique, and rectus abdominis.

Vascular supply to the breast is primarily through branches of the internal mammary artery and the lateral thoracic artery. This network provides most of the blood supply to the deeper tissues of the breast and to the nipple. The subcutaneous and retromammary fat that surrounds the glandular tissue constitutes most of the bulk of the breast and gives the breast its soft consistency. The proportions of each of the component tissues vary with age, nutritional status, pregnancy, lactation, and genetic predisposition.

For the purposes of examination, the breast is divided into four quadrants and a tail ( Fig. 17.2 ). The greatest amount of glandular tissue lies in the upper outer quadrant. Breast tissue extends from this quadrant into the axilla, forming the tail of Spence. In the axillae, the mammary tissue is in direct contact with the axillary lymph nodes.

The nipple is located centrally on the breast and is surrounded by the pigmented areola. It is composed of epithelium that is infiltrated with circular and longitudinal smooth muscle fibers. Contraction of the smooth muscle, induced by tactile, sensory, or autonomic stimuli produces erection of the nipple and causes the lactiferous ducts to empty. Tiny sebaceous glands may be apparent on the areola surface (Montgomery tubercles or follicles). Hair follicles may be present around the circumference of the areola. Supernumerary nipples or breast tissue are sometimes present along the mammary ridge that extends from the axilla to the groin (see Fig. 17.10 ).

Each breast contains a lymphatic network that drains the breast radially and deeply to underlying lymphatics. Superficial lymphatics drain the skin, and deep lymphatics drain the mammary lobules. Table 17.1 summarizes the patterns of lymph drainage.

The complex of lymph nodes, their locations, and direction of drainage are illustrated in Fig. 17.3 . The axillary nodes are more superficial and are accessible to palpation when enlarged. The anterior axillary (pectoral) nodes are located along the lower border of the pectoralis major, inside the lateral axillary fold. The midaxillary (central) nodes are high in the axilla close to the ribs. The posterior axillary (subscapular) nodes lie along the lateral border of the scapula and deep in the posterior axillary fold, whereas the lateral axillary (brachial) nodes can be felt along the upper humerus.

Review of Related History

For each of the symptoms or conditions discussed in this section, targeted topics to include in the history of the present illness are listed. Responses to questions about these topics help fully assess the patient’s condition and provide clues for focusing on the physical examination and the development of an appropriate diagnostic evaluation. Questions regarding medication use (prescription and over-the-counter preparations) as well as complementary and alternative therapies are relevant for each.

History of Present Illness

Past Medical History

• Previous breast disease: cancer, fibroadenomas, fibrocystic changes

• Known BRCA1, BRCA2, or other genetic mutation; known hereditary cancer syndrome (hereditary nonpolyposis colorectal cancer [HNPCC], Li-Fraumeni syndrome, or Cowden syndrome)

• Gender identity: e.g., female, male, non-binary, transgender woman, transgender man, sex assignment at birth

• Previous other related cancers: ovarian, colorectal, endometrial

• Surgeries: breast biopsies, aspirations, implants, reductions, mastectomies, reconstructions, oophorectomy

• Risk factors for breast cancer (see Risk Factors: “Breast Cancer”)

• Mammogram and other breast imaging history: frequency, date of last imaging, results

• Menstrual history: first day of last menstrual period; age at menarche and menopause; cycle length, duration, amount of flow, and regularity; associated breast symptoms (nipple discharge; pain or discomfort)

• Pregnancy: age at each pregnancy, length of each pregnancy, date of delivery or termination

• Lactation: number of children breast-fed; duration of time for breast-feeding; date of termination of last breast-feeding; medications used to suppress lactation

• Menopause: onset, course, associated problems, residual problems

• Use of hormonal medications: name and dosage, reason for use (contraception, menstrual control, menopausal symptom relief; gender-affirming treatment), length of time on hormones, date of termination

• Other medications: nonprescription or prescription; hormones (estrogen, progesterone), selective estrogen receptor modulators (SERMS) (tamoxifen, raloxifene), aromatase inhibitors (e.g., anastrozole, letrozole, exemestane); silicone injections

Family History

• Breast cancer: primary relatives, secondary relatives; type of cancer; age at time of occurrence; treatment and results; known BRCA1, BRCA2, or other mutation

• Other cancers: ovarian, colorectal, known hereditary cancer syndromes (breast-ovarian cancer syndrome, HNPCC, Li-Fraumeni syndrome, or Cowden syndrome)

• Other breast disease in relatives: type of disease; age at time of occurrence; treatment and results

Personal and Social History

• Age

• Breast support used with strenuous exercise or sports activities

• Amount of caffeine intake and breast tissue response (pain, fibrocystic changes)

• Breast self-awareness: frequency, at what time in the menstrual cycle

• Use of alcohol, daily amounts

• Use of anabolic steroids or marijuana