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    Related Topics

    From Lymphatic System

    Peyer’s Patches
    Lymphoid nodules in the small intestine.
    Submental Lymph Nodes
    Drain the floor of the mouth and central lower lip.
    NALT
    Nasal-associated lymphoid tissue.
    Anterior Mediastinal Nodes
    Drain anterior thoracic structures.
    Right Lymphatic Duct
    Drains right upper quadrant of the body.
    Paratracheal Nodes
    Located lateral to the trachea.
    Sacral Lymph Nodes
    Drain the pelvic floor and rectum.
    Supraclavicular Lymph Nodes
    Located above the clavicle; key in thoracic drainage.
    Apical Axillary Nodes
    Located at the apex of the axilla.
    Deep Cervical Lymph Nodes
    Located along internal jugular vein; receive lymph from head and neck.
    Subscapular Axillary Nodes
    Located along the posterior chest wall.
    Pretracheal Nodes
    Located anterior to the trachea.
    SALT
    Skin-associated lymphoid tissue.
    Lateral Axillary Nodes
    Located along the humerus in the axilla.
    Preaortic Nodes
    Located in front of the aorta.
    Red Bone Marrow
    Produces lymphocytes; site of B-cell maturation.
    Inguinal Lymph Nodes
    Drain the lower limbs and external genitalia.
    Retroaortic Nodes
    Located behind the aorta.
    Jugular Trunk
    Drains lymph from the head and neck.
    Cisterna Chyli
    Dilated sac at the start of the thoracic duct.
    Spleen
    Filters blood and initiates immune response.
    Lymph Nodes
    Small structures that filter lymph and store immune cells.
    Palatine Tonsils
    Located on each side of the oropharynx.
    Iliac Lymph Nodes
    Include external, internal, and common iliac nodes.
    GALT
    Gut-associated lymphoid tissue.

    Axillary Lymph Nodes

    Reviewed by our medical team

    Drain the upper limbs and chest wall.

    1. Overview

    The axillary lymph nodes are a group of vital lymph nodes located in the axilla (armpit region), primarily responsible for draining lymph from the upper limb, thoracic wall, breast, and portions of the upper abdominal wall. These nodes serve as critical hubs in the lymphatic system, filtering lymph fluid and supporting immune surveillance. Their strategic location makes them especially significant in the context of breast cancer staging and metastasis.

    2. Location

    The axillary lymph nodes are situated within the axillary fat pad, bordered by the pectoralis major and minor muscles anteriorly, the latissimus dorsi and subscapularis posteriorly, the thoracic wall medially, and the humerus laterally. They lie along the axillary vein and artery and are embedded in the axillary fascia.

    They are typically divided into five anatomical groups based on their position relative to surrounding structures:

    • Pectoral (anterior) group: Located along the lateral edge of the pectoralis major, near the lateral thoracic vessels. Drains anterior thoracic wall and breast.

    • Subscapular (posterior) group: Found along the subscapular vessels. Drains the posterior thoracic wall and scapular region.

    • Humeral (lateral) group: Located along the humeral (axillary) vein. Drains the upper limb.

    • Central group: Located near the base of the axilla, receives lymph from the pectoral, subscapular, and humeral groups.

    • Apical group: Located at the apex of the axilla, near the first rib and clavicle. Receives lymph from all other axillary nodes and drains into the subclavian trunk.

    3. Structure

    Axillary lymph nodes are small, bean-shaped structures encapsulated in connective tissue. Each node is organized into three primary regions:

    • Cortex: Contains lymphoid follicles rich in B lymphocytes.

    • Paracortex: Contains T lymphocytes and antigen-presenting cells for cell-mediated immunity.

    • Medulla: Contains plasma cells, macrophages, and lymph sinuses for antibody production and phagocytosis.

    Afferent lymphatic vessels carry lymph into the node, where it is filtered before exiting through efferent vessels. These efferent vessels converge into the subclavian lymphatic trunk, which drains into the venous system near the junction of the internal jugular and subclavian veins.

    4. Function

    The axillary lymph nodes perform multiple important functions:

    • Filtration of lymph: Removes pathogens, cancer cells, and debris from lymph drained from the breast, arm, and thoracic wall.

    • Immune activation: Acts as sites where antigen-presenting cells activate T and B lymphocytes to mount adaptive immune responses.

    • Regulation of lymphatic flow: Serves as relay stations that direct lymph from peripheral tissues toward the venous system.

    5. Physiological Role(s)

    The axillary lymph nodes contribute to systemic immune surveillance and regional homeostasis:

    • Infection control: Act as first responders to pathogens entering through cuts, bites, or injections in the upper limb or thoracic wall.

    • Cancer monitoring: Act as sentinel nodes for malignancies, particularly breast cancer and upper limb skin cancers.

    • Vaccine response: React to intramuscular vaccines (e.g., deltoid injections) by producing temporary lymphadenopathy due to immune activation.

    Through these mechanisms, axillary nodes help protect vital organs by preventing the systemic spread of localized infections or malignant cells.

    6. Clinical Significance

    Lymphadenopathy

    Axillary lymph node enlargement may be due to:

    • Infections: Localized (e.g., cellulitis of the arm, cat-scratch disease) or systemic (e.g., viral illnesses such as HIV or EBV).

    • Inflammatory conditions: Autoimmune diseases like lupus or rheumatoid arthritis.

    • Malignancy: Most commonly breast cancer, but also lymphoma or melanoma.

    Breast Cancer and Sentinel Lymph Node Biopsy

    The axillary lymph nodes, particularly the pectoral and central groups, are commonly involved in breast cancer metastasis. Their status is a key prognostic factor:

    • Sentinel lymph node biopsy (SLNB): A minimally invasive procedure to identify and test the first draining (sentinel) node for metastatic disease.

    • Axillary lymph node dissection (ALND): Removal of multiple axillary nodes may be required if metastasis is confirmed, though it carries risks like lymphedema and nerve injury.

    Postoperative Complications

    • Lymphedema: Swelling of the arm due to lymphatic obstruction following surgery or radiation.

    • Nerve damage: Injury to the intercostobrachial nerve during axillary surgery can lead to numbness or paresthesia in the upper medial arm.

    Vaccination-Related Lymphadenopathy

    Temporary swelling of axillary lymph nodes may occur after vaccinations (e.g., COVID-19 vaccines), especially when administered in the deltoid. This is a normal immune reaction and typically resolves within a few weeks.

    Palpation and Imaging

    Axillary nodes can be palpated during physical examination. Key signs of concern include:

    • Firmness, immobility, or matted consistency

    • Enlargement greater than 1 cm, especially if persistent

    • Associated systemic symptoms (e.g., fever, weight loss)

    Ultrasound, mammography, MRI, and biopsy are used for further evaluation when clinically indicated.

    Did you know? Lymphatic fluid can carry cancer cells from one part of the body to another, which is why cancer often spreads through the lymphatic system.