Axillary Nodes

The axillary lymph nodes are a large and clinically important collection of lymph nodes situated within the axilla. They form the principal regional lymphatic drainage system for the upper limb and also receive substantial lymphatic drainage from the breast and superficial tissues of the thoracic and upper abdominal walls.

The axillary nodes are conventionally organized into five principal groups: pectoral (anterior), subscapular (posterior), humeral (lateral), central, and apical. These groups are arranged according to their relationships with the walls, vessels, and contents of the axilla and form an interconnected pathway directing lymph toward the root of the neck.

Most lymph from the upper limb enters the humeral nodes, while a large proportion of lymph from the breast reaches the pectoral nodes. Lymph from these peripheral groups converges on the central and then apical nodes. Efferent vessels from the apical nodes form the subclavian lymphatic trunk.

Location

The axillary lymph nodes lie within the connective tissue and fat of the axilla, the pyramidal space between the upper limb and lateral thoracic wall.

Individual groups are distributed along the axillary vessels and near the anterior, posterior, and medial aspects of the axillary compartment.

Their positions correspond closely to the lymphatic vessels entering the axilla from the upper limb, breast, thoracic wall, and back.

General Features

Feature	Description
Location	Axilla
Principal groups	Pectoral, subscapular, humeral, central, and apical
Major drainage territories	Upper limb, breast, thoracic wall, and upper abdominal wall
Major upper limb pathway	Humeral nodes
Major breast pathway	Pectoral nodes
Final axillary group	Apical nodes
Efferent pathway	Subclavian lymphatic trunk

Groups of Axillary Lymph Nodes

The axillary nodes are divided anatomically into groups according to their positions within the axilla.

The peripheral groups receive lymph directly from major drainage territories, while the central and apical nodes function as progressively more proximal collecting stations.

This organization produces a general pattern of lymphatic flow from peripheral axillary nodes toward central nodes, apical nodes, and ultimately the subclavian lymphatic trunk.

Pectoral Nodes

The pectoral lymph nodes, also called the anterior axillary nodes, lie along the lateral thoracic wall near the lateral thoracic vessels and the inferior border of the pectoralis minor.

They receive lymph from the anterior and lateral thoracic wall, including a substantial portion of the breast, and from superficial tissues of the upper anterior abdominal wall.

Their efferent vessels pass primarily toward the central axillary nodes.

Subscapular Nodes

The subscapular lymph nodes, also called posterior axillary nodes, lie along the posterior axillary wall in association with the subscapular vessels.

They receive lymph from superficial tissues of the posterior thoracic wall, scapular region, and adjacent posterior shoulder.

Their efferent vessels pass mainly toward the central nodes.

Humeral Nodes

The humeral lymph nodes, also called lateral axillary nodes, are situated along the axillary vein, particularly on its medial and posterior aspects.

They receive most of the lymphatic drainage from the upper limb.

Their efferent vessels pass mainly toward the central and apical axillary nodes.

Central Nodes

The central axillary lymph nodes lie within the fat near the base and central portion of the axilla.

They receive lymph from the pectoral, subscapular, and humeral groups and therefore represent an important convergence point for lymph arriving from the upper limb and thoracic wall.

Their efferent vessels pass superiorly toward the apical nodes.

Apical Nodes

The apical axillary lymph nodes occupy the apex of the axilla near the first rib and proximal axillary vessels.

They receive lymph from the other axillary groups and may also receive lymphatic vessels accompanying the cephalic vein.

Efferent vessels from the apical nodes unite to form the subclavian lymphatic trunk.

Comparison of Axillary Node Groups

Group	Location	Major Drainage Territory	Primary Efferent Drainage
Pectoral	Anterior axillary wall near lateral thoracic vessels	Breast and anterior/lateral thoracic wall	Central nodes
Subscapular	Posterior axillary wall near subscapular vessels	Posterior thoracic wall and scapular region	Central nodes
Humeral	Along axillary vein	Most of upper limb	Central and apical nodes
Central	Central axillary fat	Receives from peripheral axillary groups	Apical nodes
Apical	Apex of axilla	Other axillary groups and selected upper limb pathways	Subclavian lymphatic trunk

Upper Limb Drainage

Most superficial and deep lymphatic vessels of the upper limb eventually reach the axillary lymph nodes.

Superficial lymphatic vessels generally accompany the major superficial veins, while deep lymphatic vessels accompany the deep arteries and veins.

The humeral axillary nodes receive the majority of this lymph before it passes toward central and apical groups.

Superficial Lymphatics of the Upper Limb

Superficial lymphatic vessels arise from networks within the skin and subcutaneous tissues of the hand, forearm, and arm.

These vessels generally follow superficial venous pathways toward the axilla.

Their routes are commonly described according to their relationships with the basilic and cephalic veins.

Lymphatics Accompanying the Basilic Vein

Many superficial lymphatic vessels from the medial side of the hand and forearm accompany the basilic vein.

Some first enter the cubital lymph nodes near the elbow before continuing proximally.

The vessels ultimately reach the humeral group of axillary nodes.

Cubital Nodes

The cubital lymph nodes, also called epitrochlear or supratrochlear nodes, are small regional nodes located near the medial aspect of the elbow.

They receive lymph from portions of the hand and forearm carried along medial superficial lymphatic pathways.

Their efferent vessels ascend toward the humeral axillary nodes.

Lymphatics Accompanying the Cephalic Vein

Superficial lymphatic vessels from the lateral upper limb commonly accompany the cephalic vein.

Some lymphatics enter deltopectoral or infraclavicular nodes before reaching the apical axillary nodes.

This pathway provides an alternative route that can partially bypass the humeral and central axillary groups.

Deep Lymphatics of the Upper Limb

Deep lymphatic vessels drain muscles, joints, periosteum, and other deep structures of the upper limb.

They generally accompany the major arteries and deep veins toward the axilla.

These vessels predominantly terminate in the humeral axillary nodes before lymph continues toward the central and apical groups.

Breast Lymphatic Drainage

The axillary nodes receive a major proportion of the lymphatic drainage from the breast.

Lymphatic vessels from breast tissue form interconnected networks that communicate with lymphatics of the skin, nipple, areola, and deeper glandular tissue.

A substantial majority of breast lymph, particularly from the lateral quadrants, drains toward the axillary nodes.

Pectoral Nodes and the Breast

The pectoral axillary nodes are the principal initial axillary group receiving lymph from much of the breast.

Lymphatic vessels travel from the breast toward nodes along the lateral thoracic vessels.

From the pectoral nodes, lymph usually passes toward the central and subsequently apical axillary nodes.

Breast to Axillary Drainage Pathway

A simplified major axillary pathway from the breast is:

Breast lymphatic vessels → pectoral axillary nodes → central axillary nodes → apical axillary nodes → subclavian lymphatic trunk.

Breast lymphatic drainage is not limited to this route. Additional pathways reach parasternal, interpectoral, infraclavicular, and other regional nodes.

Parasternal Drainage of the Breast

Medial portions of the breast can drain toward the parasternal lymph nodes located along the internal thoracic vessels.

These lymphatic pathways can communicate across the anterior thoracic wall with lymphatics of the opposite breast.

This route is anatomically important because breast lymphatic drainage is not confined to the ipsilateral axilla.

Interpectoral Nodes

Interpectoral lymph nodes, often called Rotter nodes, may occur between the pectoralis major and pectoralis minor muscles.

They can receive lymph from the breast and communicate with axillary nodal pathways.

Their presence and number vary among individuals.

Thoracic Wall Drainage

The axillary nodes receive lymph from substantial areas of the superficial thoracic wall.

The pectoral nodes receive lymph primarily from anterior and lateral regions, while the subscapular nodes receive lymph from posterior thoracic and scapular regions.

These pathways converge toward the central axillary nodes.

Upper Abdominal Wall Drainage

Superficial lymphatics of the abdominal wall show a general division around the level of the umbilicus.

Superficial tissues above the umbilicus tend to drain superiorly toward axillary lymph nodes, while tissues below the umbilicus predominantly drain toward superficial inguinal nodes.

This boundary is not absolute because superficial lymphatic networks communicate extensively.

Posterior Thoracic Wall

Superficial lymph from portions of the posterior thoracic wall and scapular region can pass toward the subscapular axillary nodes.

The subscapular vessels provide important landmarks for this nodal group.

Efferent lymph then travels toward the central and apical axillary groups.

Efferent Drainage

Lymph passing through the axillary nodal groups eventually converges on the apical nodes.

Efferent lymphatic vessels from the apical nodes unite to form the subclavian lymphatic trunk.

The subclavian trunk carries lymph from the upper limb and associated axillary drainage territories toward the central venous circulation.

Subclavian Lymphatic Trunk

A subclavian lymphatic trunk is present on each side and represents the principal terminal lymphatic pathway associated with the upper limb.

Its termination is variable. The trunk may join a major lymphatic duct or enter the venous circulation independently near the venous angle.

This variation is characteristic of terminal lymphatic anatomy.

Right-Sided Drainage

On the right, the subclavian trunk may join the right lymphatic duct or terminate independently near the junction of the right internal jugular and subclavian veins.

The right lymphatic duct itself is variable and may be formed by combinations of the jugular, subclavian, and bronchomediastinal lymphatic trunks.

Ultimately, lymph from the right upper limb returns to the venous circulation in the region of the right venous angle.

Left-Sided Drainage

On the left, the subclavian trunk may join the thoracic duct near its termination or enter the venous system independently.

The thoracic duct terminates near the junction of the left internal jugular and subclavian veins.

This provides a route by which lymph from the left upper limb returns to the bloodstream.

Overall Upper Limb Drainage Pathway

A simplified major pathway from the upper limb is:

Upper limb lymphatic vessels → humeral axillary nodes → central axillary nodes → apical axillary nodes → subclavian lymphatic trunk → central venous circulation.

Some lymphatics, particularly those accompanying the cephalic vein, may reach apical nodes through deltopectoral pathways without passing through every intermediate axillary group.

Relationship to the Axillary Vein

The axillary vein is an important landmark for the humeral and apical axillary lymph nodes.

Humeral nodes are arranged along the vein within the lateral part of the axilla, while apical nodes are associated with its proximal portion near the apex.

This relationship is important during axillary surgery because lymphatic tissue and major vascular structures lie in close proximity.

Relationship to the Axillary Artery

The axillary artery passes through the axilla with its branches and accompanying cords of the brachial plexus.

Axillary lymph nodes occupy surrounding connective tissue but are generally described according to their relationships with the axillary walls and venous system rather than the arterial divisions.

Knowledge of the artery and its branches remains essential during surgical dissection of the axilla.

Relationship to Pectoralis Minor

The pectoralis minor is an important surgical landmark in the axilla.

Its relationship to axillary lymph nodes is used in the clinical classification of axillary nodal levels in breast cancer surgery.

Nodes are categorized as Level I, Level II, or Level III according to their position relative to this muscle.

Axillary Lymph Node Levels

In breast surgery and oncology, axillary lymph nodes are commonly divided into three levels based on their relationship to the pectoralis minor muscle.

Level	Relationship to Pectoralis Minor	General Location
Level I	Lateral to the lateral border	Lower and lateral axillary region
Level II	Posterior to the muscle	Central axillary region
Level III	Medial to the medial border	Apical axillary region

This clinical level system overlaps with, but is not identical to, the traditional anatomical grouping of pectoral, subscapular, humeral, central, and apical nodes.

Level I Nodes

Level I nodes lie lateral to the lateral border of pectoralis minor.

This region includes many of the pectoral, subscapular, and humeral nodes.

These nodes often represent early axillary stations receiving lymph from the breast and upper limb.

Level II Nodes

Level II nodes lie posterior to the pectoralis minor muscle.

They include much of the central axillary nodal tissue and may include interpectoral nodes depending on the clinical classification being used.

Lymph from Level I pathways commonly progresses toward this region.

Level III Nodes

Level III nodes lie medial to the medial border of pectoralis minor toward the apex of the axilla.

They correspond largely to the apical axillary nodal region.

Efferent vessels from this region contribute to the subclavian lymphatic trunk.

Sentinel Lymph Nodes

A sentinel lymph node is the first lymph node, or one of the first nodes, expected to receive lymphatic drainage from a particular tissue or tumor.

In breast cancer, sentinel nodes are frequently located within the axillary lymphatic system.

The precise sentinel node varies according to the lymphatic drainage pathway of the individual lesion.

Clinical Examination

Axillary lymph nodes are assessed clinically by palpation of the axilla.

Because many normal nodes are small and embedded in axillary fat, they may not be readily palpable.

When enlarged, their location, size, mobility, consistency, tenderness, and relationship to surrounding tissues are assessed.

Clinical Significance

Axillary Lymphadenopathy

Axillary lymphadenopathy refers to enlargement of one or more axillary lymph nodes.

Potential causes include infection or inflammation of the upper limb or breast, systemic infection, immune disorders, lymphoma, and metastatic malignancy.

The pattern and clinical significance depend on the drainage territory and characteristics of the involved nodes.

Upper Limb Infection

Infections involving the hand, forearm, or arm can produce reactive enlargement of axillary nodes.

Lymphatic vessels carry microbial antigens and immune cells from infected tissues toward regional nodes.

Humeral nodes are particularly important because they receive most lymphatic drainage from the upper limb.

Breast Cancer

The axillary lymph nodes are among the most important regional lymph nodes in the anatomical spread of breast cancer.

Malignant cells can enter breast lymphatic vessels and travel toward the pectoral and other axillary nodes.

The presence and anatomical extent of regional nodal involvement contribute to staging and treatment planning.

Lymphatic Spread of Breast Cancer

A common anatomical route of breast cancer spread follows lymphatic drainage from the breast into the pectoral nodes and then toward central and apical nodes.

However, breast lymphatics have multiple pathways, including drainage toward parasternal and interpectoral nodes.

Individual patterns of metastatic spread therefore depend on the location of the primary lesion and its lymphatic connections.

Sentinel Lymph Node Biopsy

Sentinel lymph node biopsy is used to evaluate the first regional lymph node or nodes receiving drainage from a tumor.

In breast cancer, identification and pathological examination of sentinel nodes can provide information about regional lymphatic spread.

This approach can reduce the need for more extensive axillary surgery in appropriately selected clinical settings.

Axillary Lymph Node Dissection

Axillary lymph node dissection involves surgical removal of axillary nodal tissue for selected indications.

The procedure requires detailed knowledge of axillary vessels, the long thoracic nerve, thoracodorsal neurovascular bundle, intercostobrachial nerves, and the boundaries of the axilla.

The extent of dissection depends on the clinical indication and nodal levels being addressed.

Long Thoracic Nerve

The long thoracic nerve descends along the medial wall of the axilla on the superficial surface of the serratus anterior muscle.

Because of its proximity to axillary lymphatic tissue, it is an important structure to identify and preserve during axillary surgery.

Injury can impair serratus anterior function and contribute to winging of the scapula.

Thoracodorsal Nerve

The thoracodorsal nerve travels along the posterior axillary wall with the thoracodorsal vessels toward the latissimus dorsi.

It lies close to posterior axillary lymphatic tissue and is another important structure during nodal dissection.

Injury can weaken latissimus dorsi function.

Intercostobrachial Nerve

The intercostobrachial nerve commonly crosses the axilla to provide cutaneous sensation to the upper medial arm.

It may pass through or near axillary nodal tissue and can be encountered during lymph node surgery.

Injury may produce sensory disturbance involving the axilla and medial upper arm.

Lymphedema

Disruption or removal of axillary lymphatic vessels and nodes can impair lymphatic drainage from the upper limb.

Accumulation of protein-rich interstitial fluid can produce upper limb lymphedema.

The degree of lymphatic impairment varies according to the extent of lymphatic disruption and the availability of collateral drainage pathways.

Lymphoma

Axillary nodes may enlarge in lymphoma as part of localized or generalized lymphadenopathy.

Multiple nodes may become enlarged even without infection or disease in their usual peripheral drainage territories.

Imaging and pathological examination are used to characterize suspected lymphoid disease.

Metastatic Disease

Although breast malignancy is an important cause of axillary nodal metastasis, malignant cells can reach the axillary nodes from other tissues within their drainage territories.

Potential pathways include lesions involving the upper limb and superficial thoracic wall.

Anatomical drainage patterns can help guide investigation of unexplained axillary nodal disease.

Imaging

Axillary nodes can be evaluated using several imaging techniques depending on the clinical context.

Their location relative to the axillary vessels, pectoral muscles, chest wall, and surrounding fat helps identify the relevant nodal group or level.

Assessment considers nodal morphology, cortical appearance, internal architecture, size, and distribution.

Ultrasound

Ultrasound is useful for evaluating axillary lymph nodes because many are accessible within the superficial and intermediate soft tissues.

It can demonstrate nodal shape, cortex, fatty hilum, vascularity, and relationship to adjacent structures.

Ultrasound can also guide needle sampling when pathological evaluation is required.

Anatomical Variation

The number, size, and precise distribution of axillary lymph nodes vary considerably among individuals.

Lymphatic vessels may bypass individual groups, travel through interpectoral or deltopectoral pathways, or communicate with neighboring lymphatic territories.

These variations are especially important when considering sentinel lymph node location and patterns of metastatic spread.

Functional Importance

The axillary lymph nodes form the principal regional lymphatic system of the upper limb and an important drainage pathway for the breast and thoracic wall. Their arrangement into peripheral, central, and apical groups provides a progressively convergent route toward the subclavian lymphatic trunk.

By filtering lymph arriving from the upper limb, breast, thoracic wall, and adjacent regions, the axillary nodes expose lymph-borne antigens and cellular material to organized immune tissue and participate in regional immune surveillance.

The axillary nodes therefore have important roles in upper limb lymphatic drainage, breast drainage, lymph filtration, immune surveillance, and the regional lymphatic spread of disease.