The breast is an apocrine gland seen in both males and females. However, in females it has a specific function which is the production of milk for neonatal nutrition and immune function.

The breast has an inhomogeneous structure which is predominantly composed of adipose tissue and glandular tissue. In addition, there are also suspensory Cooper's ligaments and connective tissue such as collagen and elastin. The adult breast has nearly 14-18 lactiferous lobes which drain into lactiferous ducts which further converge to drain at the nipple-areola complex.

The glandular parenchyma is estrogen dependent, thus on attaining menopause the glandular parenchyma atrophies.

Location

The breasts are seen to overlie on the pectoralis major muscles and extend from the level of the second-to-sixth ribs:

superior: clavicle
inferior: middle of sternum
lateral: midaxillary line
medial: sternum

There is often an extension of breast tissue into the axilla called the axillary tail.

Arterial supply

internal thoracic artery perforators (second-to-fifth perforators)
thoracoacromial artery
vessels to serratus anterior
lateral thoracic artery
terminal branches of third-to-eighth intercostal perforators

Venous drainage

Nerve supply

thoracic intercostal nerve T3-T5
supraclavicular nerve from the cervical plexus

Lymphatic drainage

The drainage of lymph from the breast has significant impact on spread of malignancy and as such has a separate article: lymphatic drainage of the breast.

Development

During embryological development, breast tissue first appears as ectoderm ridges during the 6^th week of gestation. This ridge grows thicker and leads to mesodermal compression. With further proliferation of the ectodermal cells, there is a growth of the same into the mesodermal layer leading to a formation of clusters which further form lobules. In the fifth month of gestation some cords of ectodermal cells sprout from each of these lobules with the central parts undergoing apoptosis leading to formation of ducts. Similarly on the surface apoptosis occurs leading to formation of pits which protrude through the nipples after connecting with the formed ducts.

Variant anatomy

breast hypoplasia
amastia
amazia
athelia
polythelia (supernumerary nipple)
polymastia (accessory breast tissue)

Radiographic appearance

Mammography

a wide variation of homogeneously dense, milky structures (representing glandular tissue) interrupted by areas of curved or round radiolucent fat
Cooper's ligaments appear as curved, linear radiopacities
duct system is not normally visualized except near the nipple ²

See articles: mammography views; breast density.

Ultrasound

glandular tissue appears variably hyperechoic and fat appears hypoechoic
ducts appear as regular interspersed tubular, hypoechoic structures
Cooper's ligaments appear as hyperechoic, linear structures and may cause acoustic shadowing ^2-3
nipple can also cause acoustic shadowing, sometimes creating a pseudomass ³

See article: breast ultrasound.