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Central axillary lymph nodes

The central axillary lymph nodes are a cluster of fat-embedded lymph nodes located within the central portion of the axilla, deep to the pectoralis major and minor muscles. They represent Level II axillary lymph nodes and play a key role in draining the lateral quadrants of the breast, upper limb lymphatics, and axillary skin.

These nodes lie centrally above the axillary fat pad, receiving lymph from the pectoral (anterior), subscapular (posterior), and humeral (lateral) axillary nodes, and they drain into the apical (Level III) axillary nodes. Their anatomical position makes them critically important in breast cancer staging and surgical planning.

Synonyms

  • Level II axillary lymph nodes

  • Central group of axillary nodes

Location and Structure

  • Located deep within the axillary fat posterior to the pectoralis minor muscle

  • Situated centrally between the pectoral, subscapular, and humeral groups

  • Typically 3–4 nodes, but varies among individuals

  • Oval or reniform in cross-section, with a cortex, medulla, hilum, and capsule

  • Surrounded by axillary fat and connective tissue for mobility

Relations

  • Anteriorly: Pectoralis minor muscle

  • Posteriorly: Subscapularis, latissimus dorsi, and teres major muscles

  • Laterally: Humeral (lateral) axillary lymph nodes

  • Medially: Pectoral (anterior) nodes and thoracic wall

  • Superiorly: Apical axillary nodes

  • Inferiorly: Axillary fat pad and vessels

Drainage

  • Afferent drainage:

    • Pectoral (anterior) lymph nodes

    • Subscapular (posterior) lymph nodes

    • Humeral (lateral) lymph nodes

    • Axillary skin and deeper axillary tissues

  • Efferent drainage:

    • Apical (Level III) axillary lymph nodes

Function

  • Filters lymph from upper limb, breast, and axillary tissues

  • Immune surveillance through lymphocyte activation

  • Major relay center between peripheral breast nodes and central thoracic lymphatic pathways

  • Plays essential role in cancer staging and lymphatic mapping

MRI Appearance

T1-weighted images

  • Nodes appear intermediate-to-low signal cortex

  • Hilum: Typically bright due to fatty content

  • Surrounding fat: Bright, clearly outlining node borders

  • Node capsule: thin low-signal margin

T2-weighted images

  • Cortex: intermediate signal

  • Hilum: brighter than cortex

  • Fat planes: hyperintense, allowing excellent delineation

  • Internal architecture preserved with visible hilum

STIR

  • Nodes: intermediate-to-dark signal, as STIR suppresses surrounding fat

  • Cortex remains slightly darker than hilum

  • Clear depiction of node margins due to uniform fat suppression

T1 Fat-Saturated Post-Contrast

  • Normal central axillary lymph nodes show mild-to-moderate homogeneous enhancement

  • Fat suppression improves visualization of cortical and hilar enhancement

  • Hilum enhances subtly, maintaining central brightness

  • Cortical enhancement remains smooth and uniform

CT Appearance

Non-Contrast CT

  • Nodes: soft-tissue attenuation, slightly higher density than surrounding fat

  • Hilum: may appear as a small fat-density focus within the node

  • Surrounding axillary fat clearly outlines lymph node contours

  • Capsule: thin, well-defined margin

Post-Contrast CT

  • Normal nodes exhibit mild homogeneous enhancement

  • Hilar fat may remain visible as a central low-attenuation area

MRI image

Central axillary lymph nodes coronal

MRI image

Central axillary lymph nodes MRI sagittal image