CorpusHuman Anatomy
Lymphatic & ImmuneLymph node group

Axillary lymph nodes

Nodi lymphoidei axillares

Also known as: axillary nodes, pectoral nodes, apical nodes, Rotter nodes, interpectoral nodes, axillary levels I–III

About 20–40 nodes in the axillary fat, arranged in five groups (three surgical levels), that drain the upper limb, most of the breast and the thoracoabdominal wall above the umbilicus.

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Overview

Number≈ 20–40 nodes
Share of breast lymph≈ 75%

The axillary nodes lie in the fat of the axilla along the axillary vessels and their branches. Anatomically there are five groups. The anterior (pectoral) nodes lie along the lateral thoracic vessels at the lower border of pectoralis minor and receive most lymph from the breast and anterior thoracic wall. The posterior (subscapular) nodes, along the subscapular/thoracodorsal vessels in the posterior axillary fold, drain the posterior thoracic wall and scapular region. The lateral (humeral) nodes, posteromedial to the axillary vein, drain almost the whole upper limb. All three drain to the central nodes deep in the axillary fat (through which the intercostobrachial nerve passes), and these drain to the apical nodes at the apex of the axilla along the axillary vein, which also receive vessels accompanying the cephalic vein. Efferents from the apical nodes form the subclavian trunk; some pass to the inferior deep cervical (supraclavicular) nodes.

Surgeons describe levels relative to pectoralis minor: level I lateral/inferior to it (anterior, posterior and lateral groups), level II deep to it (central nodes and the interpectoral Rotter nodes between pectoralis major and minor), and level III medial/superior to it (apical, infraclavicular nodes). Breast cancer usually spreads in order from level I to level III.

About 75% of breast lymph, chiefly from the lateral quadrants, drains to the axillary nodes (most of the remainder to parasternal nodes along the internal thoracic vessels, with some to the opposite breast or abdominal wall).

Location

In the axillary fat pad, along the axillary vessels and their thoracic branches, bounded by pectoralis major/minor anteriorly, subscapularis posteriorly and serratus anterior medially.

Parts & subdivisions

  1. Anterior (pectoral) group
    Along the lateral thoracic vessels at the inferior border of pectoralis minor; breast and anterior chest wall above the umbilicus. Level I.
  2. Posterior (subscapular) group
    Along the subscapular vessels on the posterior axillary wall; posterior thoracic wall and scapular region. Level I.
  3. Lateral (humeral) group
    Along the axillary vein; most of the upper limb. Level I.
  4. Central group
    Deep in the axillary fat near the base; receive from the three groups above. Level II. Enlargement can compress the intercostobrachial nerve, referring pain to the medial arm.
  5. Interpectoral (Rotter) nodes
    Between pectoralis major and minor; receive some breast lymph. Level II.
  6. Apical group
    At the apex along the axillary vein medial to pectoralis minor; receive all other groups and the cephalic-vein lymphatics; give rise to the subclavian trunk. Level III.

Anatomy

Lymphatic drainage

Pectoral, subscapular and humeral groups → central → apical → subclavian trunk → thoracic duct (left) or right lymphatic duct (right); some apical efferents → inferior deep cervical nodes.

Relations

Axillary artery and vein, brachial plexus cords, long thoracic nerve (on serratus anterior), thoracodorsal nerve (with subscapular vessels) and intercostobrachial nerve.

Function

  • Filter lymph from the upper limb, breast, and the thoracic and upper abdominal wall (skin and superficial tissues above the umbilicus, front and back).

Clinical significance

Breast cancer staging and surgery

Sentinel lymph node biopsy (radiocolloid ± blue dye) has largely replaced routine axillary lymph node dissection for clinically node-negative breast cancer. Dissection carries higher risks of arm lymphoedema, numbness of the medial arm (intercostobrachial nerve), winged scapula (long thoracic nerve → serratus anterior) and weak adduction/internal rotation (thoracodorsal nerve → latissimus dorsi).

Axillary lymphadenopathy

Causes include upper-limb or breast infection, cat-scratch disease (Bartonella henselae), breast cancer, lymphoma, metastatic melanoma, silicone implant leakage and recent ipsilateral vaccination (e.g. mRNA COVID-19 vaccines produce transient nodal enlargement on mammography).

Mnemonics

Drainage order — "three feed one, one feeds the apex"

The three peripheral groups — anterior (pectoral), posterior (subscapular) and lateral (humeral) — drain to the central group, which drains to the apical group; the apical nodes form the subclavian trunk. Levels I → II → III follow the same order relative to pectoralis minor.

Test yourself

Approximately what proportion of lymph from the breast drains to the axillary lymph nodes?
  1. ≈ 25%
  2. ≈ 50%
  3. ≈ 75%
  4. ≈ 100%

Answer: ≈ 75%

About 75% of breast lymph (especially from the lateral quadrants) passes to the axillary nodes, mostly to the pectoral (anterior) group first; most of the rest goes to parasternal nodes. This is why sentinel node biopsy and axillary staging are central to breast-cancer management.

More lymphatic & immune system questions

Compiled from standard anatomy and physiology references — see the Lymphatic & Immune System sources. For education only; not medical advice.