El tejido mamario incluye grasa subcutánea, estroma y parénquima sostenido por bandas fibrosas conocidas como ligamentos suspensorios de Cooper, vasos sanguíneos, nervios y linfáticos. El tejido pigmentado areolar contiene folículos pilosos, glándulas sudoríparas apocrinas y tubérculos de Morgagni. Areola contiene apertura de 8 a 20 ductos mayores.
The breasts are large, modified sebaceous glands contained within the superficial fascia of the anterior chest wall. A lateral projection of glandular tissue extends from the upper, outer portion of the breast toward the axilla and is called the axillary tail of Spence. The average weight of the adult breast is 200 to 300 g during the menstruating years. The mature breastconsists of approximately 20% glandular tissue and 80% fat and connective tissue. The periphery of breast tissue is predominantly fat, and the central area contains more glandular tissue.
Figure 1 The structures of the breast. (From Shah P [ed]: Breast. In Standring S [ed]: Gray's Anatomy. London, Elsevier Churchill Livingstone, 2005, p 969, fig 58-1A.)
The breast is composed of 12to 20 lobes arranged in radial fashion from the nipple. Each lobe is triangular and has one central excretory duct that opens to the exterior at the nipple. Milk originates in the secretory cells of the alveoli. It is subsequently transported by the branching collecting ducts of the lobules into the lactiferous sinuses and terminally into the excretory ducts of each respective lobe of the breast.There is a wide range in number of lobules, between 10 and 100, in each lobe of the breast. Montgomery glands are accessory glands located around the periphery of the areola. Because they are structurally intermediate between true mammary and sebaceous glands, they can secrete milk. Fibrous septa, Cooper's ligaments, extend from the skin to the underlying pectoralis fascia. They are believed tooffer support to the breast. Invasion of these ligaments by malignant cells produces skin retraction, which is a sign of advanced breast carcinoma.
Figure 2 Histologic photograph of a mammary lobule. Note the ductal tissue surrounded by fibrous tissue. Terminal ductules (TD) surround the central ductule (ID). EF, extralobular fibrocollagenous tissue. (From Stevens A, Lowe J: HumanHistology, 3rd ed. Philadelphia, Elsevier Mosby, 2005, p 390.)
Figure 3 Lactating breast. (From Shah P [ed]: Breast. In Standring S [ed]: Gray's Anatomy. London, Elsevier Churchill Livingstone, 2005, p 969, fig. 58-1B.)
The lymphatic distribution of the breast is complex. Approximately 75% of the lymphatic drainage goes to regional nodes in the axilla. The axilla contains a varying numberof nodes, usually between 30 and 60. Other metastatic routes include lymphatics adjacent to the internal mammary vessels. After direct spread into the mediastinum, lymphatic drainage may go to the intercostal glands, which are located posteriorly along the vertebral column, and to subpectoral and subdiaphragmatic areas. Lymph drainage usually flows toward the most adjacent group of nodes. Thisconcept represents the basis for sentinel node mapping in breast cancer. In most instances breast cancer spreads in an orderly fashion within the axillary lymph node basin based on the anatomic relationship between the primary tumor and its associated regional (sentinel) nodes. However, lymphatic metastases from one specific area of the breast may be found in any or all of the groups of regionalnodes. In a large multicenter study, Krag and colleagues validated the use of sentinel node biopsy in women with breast cancer. All of the women studied had positive nodes. However, in only 3% of these women did the only positive node occur outside of the axilla. Metastases from one breast across the midline to the other breast or chest wall occur occasionally.
Figure 4 Lymph vessels of...