Sonographic Anatomy of the Breast and Axilla

4 Sonographic Anatomy of the Breast and Axilla

Gross Anatomy


Anatomically the breast is a modified sweat gland lying within the deep and superficial layers of superficial pectoral fascia. Viewing a schematic sagittal section of the breast turned 90° to correlate with ultrasonographic positioning, we observe the following anatomic structures (from anterior to posterior), which can also be visualized with ultrasound (Tables 4.1, 4.2): skin, subcutaneous fat, Cooper ligaments, the superficial mammary fascia, the breast parenchyma (with ducts and lobules), interlobar fibrofatty tissue, the deep mammary fascia, retromammary fat, muscle fascia, the pectoralis major and minor muscles, the ribs and intercostal spaces, and finally the pleura and lung (Fig. 4.1).

The breast consists of a varying mixture of tissue components, and its composition depends on age, hormonal influences, structural changes (congenital, degenerative, or pathologic), and individual characteristics (Tables 4.3, 4.4). As a general rule, the breast tissue of young women consists mostly of parenchyma and contains little fat. With aging, the glandular tissue of the breast is replaced by connective tissue and fat. But there is great individual variation, so that the breasts of young multiparous women who have nursed their infants are predominantly fatty, and even in young girls a substantial portion may consist of fat, especially if the breasts are large.

Conversely, the breasts of older women who receive postmenopausal hormone replacement may respond by increasing fibro-glandular density, and many older women may have mammographically dense breasts, the density reflecting the fibrous (rather than glandular) predominance of their breast tissue. This should be considered in breast examinations as it will influence the overall interpretation of clinical, sonographic, and mammographic findings.

The structural composition of the breast varies with age, functional status, and individual differences in tissue distribution and quantitative make-up.


Fig. 4.1 Gross anatomy of the breast. PMa = pectoralis major muscle, PMi = pectoralis minor muscle.

Table 4.1 Gross anatomy of the female breast (sequence of tissue layers from anterior to posterior)

image Skin

image Subcutaneous fat

image Cooper ligaments

image Superficial mammary fascia

image Breast parenchyma with

– Lobules

– Lactiferous ducts

– Interlobar connective tissue

– Fat

image Deep mammary fascia

image Retromammary fat

image Muscle fascia

image Pectoralis major muscle

image Pectoralis minor muscle

image Ribs and intercostal muscles

image Pleura

Table 4.2 Echogenicity of the various breast tissues

Anatomic structure









tissue Hyperechoic

Subcutaneous fat


Fatty infiltration


Retromammary fat


Cooper ligaments


Lactiferous ducts


* Intraductal secretions appear as echo-free fluid, but proliferative changes and inspissated secretions may produce low-level internal echoes.

Table 4.3 Principal components of the female breast

image Fat

image Parenchyma

– Alveoli

– Lactiferous ducts

– Intralobar connective tissue (hormonally responsive)

image Interlobar connective tissue

image Axilla

Table 4.4 Parenchymal patterns in breast ultrasound

image Homogeneous hyperechoic pattern

– Young women

– Good readability

image Heterogeneous hyperechoic pattern

– Scant fatty infiltration

– Middle-aged women

– Good or moderate readability

image Partially involuted or involuted pattern

– Predominantly hypoechoic with connective-tissue septa

– Older women

– Moderate readability

image Fibrotic pattern (heterogeneously hypoechoic)

– Young and middle-aged women

– Poor readability

Parasternal Region

The internal thoracic artery descends on either side of the sternum (Fig. 4.2

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Dec 26, 2015 | Posted by in BREAST IMAGING | Comments Off on Sonographic Anatomy of the Breast and Axilla

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