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.
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.
- 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
- axillary vein
- internal thoracic vein
- posterior intercostal vein
- thoracic intercostal nerve T3-T5
- supraclavicular nerve from the cervical plexus
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.
During embryological development, breast tissue first appears as ectoderm ridges during the 6 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.
- breast hypoplasia
- polythelia (supranumerary nipple)
- polymastia (accessory breast tissue)
- a wide variation of homogeneously dense, milky structures (representing glandular tissue) interrupted by areas of curved or round radiolucent fat
- Cooper's ligaments appears as curved, linear radiopacities
- duct system is not normally visualized except near the nipple
See articles: mammography views; breast density.
- 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
- nipple can also cause acoustic shadowing, sometimes creating a pseudomass
See article: breast ultrasound.
- T1: fat has moderate high signal; glandular, ductal and connective tissue has low signal
- T1C+: normal breast tissue is typically non-enhancing
See article: breast MRI.