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Lymphatic drainage of the breast: want to learn more about it?

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Lymphatic drainage of the breast

The lymphatic system plays an essential role in systemic immunity, fluid homeostasis, and returning tissue fluid and macromolecules to the circulation. Lymphatic drainage plays a significant role in the pathology and treatment of breast cancer; globally the most frequently diagnosed malignancy and leading cause of death due to cancer in women.

Malignant cells traveling within the lymphatic system are a common mechanism of tumor metastasis, and examination of lymphatic tissue is essential for cancer prognosis and staging. Advances in lymph node harvesting have improved survival and reduced morbidity from breast cancer treatment. Moreover, lymphatic vessel disruption, a common side effect of breast cancer therapy, can result in significant morbidity.

Key facts about the lymphatic drainage of the breast
Drainage pattern

Axillary lymph nodes - they receive 75-90% of the breasts' lymph, which passes through a sentinel lymph node situated at the lateral border of pectoralis major

Internal mammary lymph nodes - they receive 10-25% of the breast's lymph

Axillary lymph nodes groups

Apical axillary (subclavicular) group

Brachial (lateral) group

Central group

Subscapular (posterior) group

Interpectoral (Rotter's nodes) group

Pectoral (external mammary) group

Infraclavicular (deltopectoral) group

Internal mammary (parasternal) group

Clinical points Breast cancer, lymphedema

Lymphatics

Overview

The lymphatic system is comprised of:

The lymphatic system (diagram)

It is a unidirectional low-pressure network of vessels that run parallel to blood vessels and are found in all regions of the body except the central nervous system and bone marrow.

Like blood plasma, lymph contains interstitial fluid, proteins, clotting factors and leukocytes. Though most of the blood exchanged in a capillary network reenters venous circulation, about 10% is extruded into the interstitial space and must be returned to maintain fluid balance. Lymphatic capillaries contain a single-layer endothelium with loose junctions in the basement membrane that facilitate the entry of cells, macromolecules, and fluid.

Lymphatic vessels

Like veins, lymphatic vessels contain valves and have a smooth muscle endothelial layer which creates a pressure gradient that is further maintained through skeletal muscle contraction, respiratory movement, and gravity. Lymphatic capillaries drain into pre-collectors which sequentially drain into collecting vessels and lymph nodes. Efferents from lymph nodes coalesce into larger vessels and regional lymphatic trunks.

Finally, the right upper torso, including right arm and breast, drain into the right lymphatic duct which empties into the right subclavian vein. The rest of the body, including the left arm and breast, lower extremities, and gastrointestinal tract, drain into the thoracic duct which empties into the left subclavian vein.

Lymph nodes

Lymph nodes are encapsulated bean-shaped structures distributed along the lymphatic system that filter lymph of microorganisms and tumor cells. An ideal location for antigen presentation, lymph nodes are essential for cellular immunity. Three paired lymph node basins, the cervical, axillary and inguinal nodes are located at the neck, axillae, and groin respectively.  

Afferent lymphatic collectors drain into sinuses between germinal centers within the node. These germinal centers contain phagocytic cells, such as macrophages, which accumulate foreign material, including the radiolabeled colloids and dyes used to localize lymph nodes during breast cancer treatment.

If you want to learn more details about the lymphatic system, take a look at the following:

Lymphatic drainage of the breast

Functional drainage of the breast

Most (75-90%) of the lymphatic drainage of the breast is to the ipsilateral (same side) axillary nodes. Nearly all lymphatics of the breast drain along a subdermal plane into the axillae, typically  collecting in a single sentinel lymph node at the lateral border of the pectoralis major muscle.

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Superficial lymphatics of the nipple and areola collect in a dense network of pre-collectors known as the Sappey subareolar plexus. Lymphatics in the breast parenchyma originate in the interlobular tissue and within the walls of the lactiferous ducts.

A variable degree of deep breast tissue, particularly of the medial breast, may collect into lymphatic vessels that perforate the deep fascia to drain into internal mammary nodes. Lymphatics may also pass through tiny interval nodes within the breast parenchyma. Sporadic drainage to the subscapular, subclavicular, supraclavicular, or contralateral internal mammary nodes can occur.  

Groups of axillary lymph nodes draining the breast (diagram)

Axillary lymph nodes

The axillary lymph node chain may be divided into six groups:

The apical axillary group

Also known as the subclavicular group, they contain 8-12 nodes between the superior border of the pectoralis minor muscle and the clavicle, lateral to the first rib. This group receives drainage from all other levels of axillary nodes and drains into the subclavian trunk, which flows into the thoracic duct on the left and the right lymphatic trunk on the right side of the body.

The brachial group

Also known as the axillary vein or lateral group, they consist of 4-6 nodes medial and posterior to the axillary vein and receive the majority of drainage from the upper extremity and drains into the apical axillary group.

The central group

Lying deep to the pectoralis minor muscle within adipose tissue of the axilla, they contain about 4-5 nodes and receive drainage from the breast, the brachial group, the pectoral group, and the subscapular group.    

The subscapular group

Also known as the posterior or scapular group, they consist of 5-7 nodes on the lateral edge of the scapula, anterior to the subscapularis muscle; they receive drainage from the posterior neck, shoulder, and trunk.

The interpectoral group

Also known as Rotter’s nodes, they consist of 1-4 nodes between the pectoralis major and minor muscles and receive lymph drainage directly from the breast, draining into the apical axillary and pectoral group.  

The pectoral group

Also known as the anterior or external mammary group, they contain 5-6 nodes along the lateral thoracic vessels at the inferior border of the pectoralis minor and superior border of the pectoralis major. They receive drainage from the lateral aspect of the breast and abdominal wall, and drain into the central group.    

The infraclavicular group

Also known as the deltopectoral group, while not part of the axillary chain, lie in the region bordered by the clavicle, deltoid and pectoralis major muscles. Surrounding the cephalic vein, this group receives drainage from the forearm and hand.  

The internal mammary nodes

Also known as the parasternal group, these nodes travel along the internal mammary artery and vein within the intercostal spaces and deep to the parietal pleura. Perforating lymphatics accompany perforating branches of the internal mammary artery through the deep fascia and pectoralis muscles. Variations in blood supply to the breast via these perforators explain why, in all quadrants of the breast, cancer has the potential to metastasize via internal mammary lymphatics, especially in the deep medial aspect of the breast.

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Lymphatic drainage of the breast: want to learn more about it?

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