The axillary lymph nodes or armpit lymph nodes are

lymph nodes A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that inclu ...

in the human

armpit The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm and the thoracic cage, bounded superior ...

. Between 20 and 49 in number, they drain lymph vessels from the lateral quadrants of the breast, the superficial lymph vessels from thin walls of the chest and the

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...

above the level of the navel, and the vessels from the upper limb. They are divided in several groups according to their location in the armpit. These lymph nodes are clinically significant in

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a r ...

, and

metastases Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then ...

from the breast to the axillary lymph nodes are considered in the

staging Staging may refer to: Computing * Staging (cloud computing), a process used to assemble, test, and review a new solution before it is moved into production and the existing solution is decommissioned * Staging (data), intermediately storing data b ...

of the disease.

Structure

The axillary lymph nodes are arranged in six groups: # Anterior (pectoral) group: Lying along the lower border of the

pectoralis minor Pectoralis minor muscle () is a thin, triangular muscle, situated at the upper part of the chest, beneath the pectoralis major in the human body. Structure Attachments Pectoralis minor muscle arises from the upper margins and outer surfaces ...

behind the pectoralis major, these nodes receive lymph vessels from the lateral quadrants of the breast and superficial vessels from the anterolateral abdominal wall above the level of the umbilicus. # Posterior (subscapular) group: Lying in front of the

subscapularis muscle The subscapularis is a large triangular muscle which fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the shoulder-joint. Structure It arises from its medial two-thirds and So ...

, these nodes receive superficial lymph vessels from the back, down as far as the level of the

iliac crest The crest of the ilium (or iliac crest) is the superior border of the wing of ilium and the superiolateral margin of the greater pelvis. Structure The iliac crest stretches posteriorly from the anterior superior iliac spine (ASIS) to the poster ...

s. # Lateral group: Lying along the medial side of the axillary vein, these nodes receive most of the lymph vessels of the upper limb (except those superficial vessels draining the lateral side—see infraclavicular nodes, below). # Central group: Lying in the center of the axilla in the axillary fat, these nodes receive lymph from the above three groups. # Infraclavicular (deltopectoral) group: These nodes are not strictly axillary nodes because they are located outside the axilla. They lie in the groove between the deltoid and pectoralis major muscles and receive superficial lymph vessels from the lateral side of the hand, forearm, and arm. # Apical group: Lying at the apex of the axilla at the lateral border of the 1st rib, these nodes receive the efferent lymph vessels from all the other axillary nodes. The apical nodes drain into the subclavian lymph trunk. On the left side, this trunk drains into the

thoracic duct In human anatomy, the thoracic duct is the larger of the two lymph ducts of the lymphatic system. It is also known as the ''left lymphatic duct'', ''alimentary duct'', ''chyliferous duct'', and ''Van Hoorne's canal''. The other duct is the righ ...

; on the right side, it drains into the

right lymphatic duct The right lymphatic duct is an important lymphatic vessel that drains the right upper quadrant of the body. It forms various combinations with the right subclavian vein and right internal jugular vein. Structure The right lymphatic duct course ...

. Alternatively, the lymph trunks may drain directly into one of the large veins at the root of the neck.

Breast cancer

About 75% of

lymph Lymph (from Latin, , meaning "water") is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues ...

from the breasts drains into the axillary lymph nodes, making them important in the diagnosis and

of breast cancer. A doctor will usually refer a patient to a surgeon to have an axillary lymph node dissection to see if the cancer cells have been trapped in the nodes. For clinical stages I and II breast cancer, axillary lymph node dissection should only be performed after first attempting sentinel node biopsy., which cites various primary research studies. If cancer cells are found in the nodes it increases the risk of metastatic breast cancer. Another method of determining breast cancer spread is to perform an endoscopic axillary sentinel node biopsy. This involves injecting a dye into the breast lump and seeing which node it first spread to (the

sentinel node In computer programming, a sentinel node is a specifically designated node used with linked lists and trees as a traversal path terminator. This type of node does not hold or reference any data managed by the data structure. Benefits Sentinel ...

). This node is then removed and examined. If there is no cancer present, it is assumed the cancer has not spread to the other lymph nodes. This procedure is often less invasive and less damaging than the axillary lymph node dissection. The estimated risk of lymphedema following sentinel lymph node procedure is less than 3%. The approximate risk of lymphedema following axillary lymph node dissection is 10-15% and this can slightly increase with the addition of radiotherapy and chemotherapy to as much as 20-25% depending on the extent of dissection, extent of radiotherapy fields, and history of chemotherapy. On CT scan or

MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...

, axillary lymphadenopathy can be defined as solid nodes measuring more than 1.5 cm without fatty hilum.Page 559
in: Lymph nodes may be normal up to 3 cm if consisting largely of fat. Axillary lymph nodes are included within the standard tangential fields in radiotherapy for breast cancer. In the case of comprehensive nodal irradiation, which includes axillary levels I, II, and III, as well as a supraclavicular lymph node field, there is a risk of damage to brachial plexus. The risk is estimated to be less than 5% as the brachial plexus radiation tolerance according to (Emami 1991) is 60 Gy in standard fractionation (2 Gy per fraction). A common prescribed dose for breast cancer with comprehensive nodal fields would be 50 Gy in 25 fractions with a boost planned to the lumpectomy cavity in the breast or scar on the chest wall if it is a mastectomy. If brachial plexopathy does occur, it is generally a late effect and may not manifest itself until 10 or 15 years later, and usually presents with slight painless muscular atrophy. Malignancies in the gastrointestinal system like

gastric cancer Stomach cancer, also known as gastric cancer, is a cancer that develops from the lining of the stomach. Most cases of stomach cancers are gastric carcinomas, which can be divided into a number of subtypes, including gastric adenocarcinomas. Lymph ...

can metastasize to the left axillary lymph node which is called "Irish’s node".

Additional images

File:Gray606.png, The superficial lymph glands and lymphatic vessels of the upper extremity

Structure

Breast cancer

Additional images

See also