Breast Anatomy & Physiology

Anatomy Visualization


Interactive Cutaway

Front View

The female brest is a modified sebaceous gland which lies between the 2nd and 6th rib and extends from the sternum to the mixaxillary line.

About two-thirds of the upper portion of the breast is superficial to the pectoralis major muscle, while the lower lateral one-third lies on top of the serratus anterior muscle.

A small portion of mammary tissue extends into the axillary region known as the tail of Spence.

Side View

Fatty tissue represents the bulk of the breast. It surrounds the glandular tissue

Lobes produce milk and communicate to the nipple surface via lactiferous ducts and sinuses. There are about 15-20 lobes in one breast.

Lactiferous sinuses

Lacteriferous ducts

Fibrous bands (Cooper's ligaments) extend from under the skin and attach to the underlying muscle, supporting the glandular tissue

The glandular, fibrous, and fatty components of breast tissue vary with such factors as age, stateof nutrition, and pregnancy

Blood Supply

Blood supply to the breast is important when considering the hematological spread of cancer cells.

The major blood supply is provided by the anterior perforating branches of the internal mammary artery as well as branches of the lateral thoracic arterys.
Lymphatics

Axillary lymph nodes represent the main lymphatic drainage pathway of the breast, receiving 75% of the total lymph.

The axillary nodal group include the:

  • central nodes which are the most frequently felt and located along the chestwall high in the axilla.
  • pectoral nodes along the lower border of the pectoralis major muscle.
  • subscapular nodes located posteriorly
Other drainage pathways course through the infraclavicular and supraclvicular nodes toward the midline to the parasternal nodes and acorss the midline to the opposite breast. These connections to the contralateral breast may play a role in metastatic breast disease.
Polythelia

Polythelia (more than two nipples) may occur as a congenital anomaly anywhere along the embryonic ridge of tissue known as the "milk line"

These are referred to as supernumerary or accessory nipples. they are often mistaken for moles.

Polythelia is inherited as an autosomal dominant trait and occurs in about 10% of the population.

 
Breast Tissue Histology
Invasive Carcinomas
  • Infiltrating ductal carcinoma 75%
  • Medullary 5%
  • Mucinous (collid) 2%
  • Tubular 2%
  • Adenocyctic 0.1%
  • Papillary 0.3%
  • Infiltrating lobular carcinoma 5%
  • Other 10.6%

--figures are approximate

 
STypes of Breast Masses
Type
Fibrocystic
Fibroandenoma
Carcinoma

Appearance
Patient Age
25-60
10-55
25-85
Number
1 or more
1
1
Shape
round
round
irregular
Delimitation
well deliminited
well deliminited
poorly deliminited
Retraction
absent
absent
present
Tenderness
present
absent
absent
Consistency
elastic
firm
stony hard
Mobility
mobile
mobile
fixed
Description
 usually found in both breasts; often enlarged and become tender just prior to the beginning of menses most common neoplasm for women under 25 years of age; usually solid and painless; occur twice as often in African-American women poorly delimited; usually stony hard and fixed in position; do not change with the menstrual cycle
Key Points
  • The major components of the breast include glandular, fibrous, and fatty tissue
  • The majority of lymph drained from the breast tissue courses through the axillary nodes
  • Documentation of breast lesions may be described according to the distance from the nipple and quadrant of occupation. Orientation according to a "clock" may also be used.