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Axillary lymph nodes

The axillary lymph nodes are a vital cluster of lymph nodes located in the axilla (armpit), forming one of the largest and most clinically significant nodal basins in the body. They are typically classified into five anatomical groups:

  • Anterior (pectoral): along the lateral thoracic vessels, draining the anterior thoracic wall and breast

  • Posterior (subscapular): along the subscapular vessels, draining the posterior thoracic wall and scapular region

  • Lateral (humeral): along the axillary vein, draining most of the upper limb

  • Central: embedded within axillary fat, receiving drainage from the anterior, posterior, and lateral groups

  • Apical: at the apex of the axilla, receiving drainage from all other axillary groups and emptying into the subclavian lymph trunk

These nodes are essential for lymphatic drainage of the upper limb, breast, and thoracic wall, making them key landmarks in oncology (especially breast cancer staging), infection, and systemic disease.

Synonyms

  • Lymphonodi axillares

  • Axillary nodal basin

  • Axillary lymphatic group

  • Axillary nodal stations

Function

  • Drain lymph from the upper limb, breast, scapular region, and thoracic wall

  • Act as biological filters, trapping pathogens, cancer cells, and debris before lymph enters systemic circulation

  • Facilitate immune surveillance and antigen presentation via lymphocytes

  • Provide critical staging information in breast cancer, melanoma, and lymphoma

  • Serve as sentinel nodes, the first nodal station involved in many malignancies

MRI Appearance

T1-weighted images:

  • Normal nodes appear as oval structures with a hypointense cortex and a hyperintense central fatty hilum

  • Pathological nodes (malignant or inflamed) often appear rounder, enlarged, and with loss of central fatty hilum

  • Cortical thickening >3 mm is suspicious for disease

T2-weighted images:

  • Cortex appears intermediate to hyperintense

  • Fatty hilum is bright on T2 and helps identify benign nodes

  • Inflamed nodes show increased T2 signal, while metastatic nodes may show irregular or heterogeneous signal

STIR (Short Tau Inversion Recovery):

  • Fat suppression makes nodes stand out as intermediate or hyperintense structures against dark axillary fat

  • Normal nodes remain relatively low to intermediate signal; infected or malignant nodes appear brighter and more conspicuous

  • Useful for identifying subtle edema, infiltration, or early nodal disease

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal nodes enhance homogeneously with preserved fatty hilum

  • Malignant nodes may enhance heterogeneously, often with cortical enhancement and absent hilum

  • Rim enhancement may indicate necrosis or abscess within the node

CT Appearance

Non-contrast CT:

  • Normal nodes appear as soft tissue density structures within axillary fat

  • Benign nodes are usually oval and <1 cm short-axis diameter, with visible fatty hila

  • Enlarged or rounded nodes raise suspicion for pathology

Contrast-enhanced CT (CECT):

  • Enhances nodal cortex and vasculature

  • Benign nodes: oval, homogeneous enhancement, fatty hilum preserved

  • Malignant nodes: rounded, heterogeneous enhancement, loss of fatty hilum, possible necrosis

  • CT is essential for breast cancer staging, lymphoma, and metastatic disease evaluation

MRI image

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CT image

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MRI image

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CT image

Axillary lymph nodes CT AXIAL SHOULDER IMAGE