What is a breast?
A breast contains (1) glands (glandular tissue of the tubulo-alveolar type), (2) fibrous tissue connecting its lobes and (3) interlobar adipose/fatty tissue. The mammary gland is enclosed by subcutaneous tissue, not as a distinct capsule, but sending in many septa to support its lobules. The breast is a rounded eminence that lies between the skin and the chest wall. Its shape varies greatly in individuals and races and at different ages, being hemispherical, conical, variably pendulous, piriform or thin and flattened. It is largely composed of adipose tissue, except during lactation; its consistency, shape and size primarily depend on this. The glands inside the breast produce milk after a woman delivers a baby. Each gland is also called a lobule, and many lobules make up a lobe. There are 15 to 20 lobes in each breast. The milk gets to the nipple from the glands by way of tubes called lactiferous ducts. Milk distends the alveoli in the glands as well as the lactiferous ducts (one from each lobe) which converge to the areola and form beneath it variable lactiferous sinuses which may serve as reservoirs.
Vascular system of the breast
The arteries supplying the mammary glands are from the thoracic branches of the axillary and from the internal thoracic and intercostal arteries.
The veins form an anastomotic venous circle "circulus venosus" at the papillary base. From this and from the glandular tissue, veins carry blood to the periphery to end in the axillary and internal thoracic veins.
Nervous system of the breast
The nerves are from the anterior and lateral cutaneous branches of the fourth to sixth thoracic spinal nerves which also convey sympathetic fibres to the mamma; however secretory activities of the gland largely controlled by ovarian and hypophyseal hormones. The papilla has a dense nervous plexus supplying many receptors, such as Messner's corpuscles and Merkel's discs and also free terminals; these are essential in signaling sucking to the central nervous system (vide supra).
Lymphatic system of the breast:
Mammary lymphatic drainage:
The lymphatic system has a very well-developed and rich network of lymphatic vessels all over and around the breasts that drains into the lymph nodes of the sub-axillary zones. Lymph nodes are small, pea-sized tissular structures that act as filters and help clean the lymph, and therefore get enlarged when they happen to filter viruses and toxic substances.
Lymph vessels of the mammary gland start in a plexus in the interlobular connective tissue and walls of the lactiferous ducts, communicating with a cutaneous sub-areolar plexus around the nipple. The gland is also said to connect with a plexus of minute vessels on the subjacent deep fascia; this connection plays little part in normal lymphatic drainage nor in early spread of carcinoma (Turner-Warwick, 1959).
It offers an alternative route when the usual pathways are obstructed. Efferent vessels directly from the gland pass round the anterior axillary border through the axillary fascia to the pectoral lymph nodes; some may pass directly to the subscapular nodes.
From the gland's superior region a few vessels pass to the apical axillary nodes, sometimes interrupted in the infraclavicular nodes or in small, inconstant interpectoral nodes.
Axillary nodes receive more than 75 % of lymph from the gland, the remainder largely draining to the parasternal nodes from the medial and lateral parts of the organ; these vessels accompany perforating branches of the internal thoracic artery. Lymphatic vessels occasionally follow lateral cutaneous branches of the posterior intercostal arteries to the intercostal nodes.
Enlargement of the axillary nodes is frequent in malignant disease and infective processes affecting the upper back and shoulder, the front of the chest and mammary gland, upper antero-lateral abdominal wall or upper limb.
In operations for mammary carcinoma, musculus pectoralis major, its deep fascia and surrounding muscles were usually removed "en bloc" because of the wide ramifications of its lymphatics.
Axillary nodes, the sternocostal head of musculus pectoralis major and frequently musculus pectoralis minor were also removed to ensure complete removal of the affected lymphatics and nodes. some, particularly with more effective diagnostic techniques, now advocate less radical extirpation.
What is breast cancer?
Collections of cells that are growing abnormally or without control are called tumors. Tumors that do not have the ability to spread throughout the body may be referred to as "benign" and are not thought of as cancerous. Tumors that have the ability to grow into other tissues or spread to distant parts of the body are referred to as "malignant." Malignant tumors within the breast are called "breast cancer". Theoretically, any of the types of tissue in the breast can form a cancer, cancer cells are most likely to develop from either the ducts or the glands. These tumors may be referred to as "invasive ductal carcinoma" (cancer cells developing from ducts), or "invasive lobular carcinoma" (cancer cells developing from lobes).
Sometimes, precancerous cells may be found within breast tissue, and are referred to as ductal carcinoma in-situ (DCIS) or lobular carcinoma in-situ (LCIS). DCIS and LCIS are diseases in which cancerous cells are present within breast tissue, but are not able to spread or invade other tissues. DCIS represents about 20% of all breast cancers. Because DCIS cells may become capable of invading breast tissue, treatment for DCIS is usually recommended.
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