Subscapular Axillary Nodes

1. Overview

The subscapular axillary lymph nodes—also known as the posterior axillary nodes—are one of the five main groups of axillary lymph nodes. Located along the posterior wall of the axilla, they play a crucial role in the drainage of lymph from the posterior thoracic wall, scapular region, and parts of the upper limb. These nodes are essential for immune defense in the upper back and shoulder regions and serve as a key relay point for lymphatic flow toward the central and apical axillary nodes.

2. Location

The subscapular nodes are situated in the posterior axillary fold, specifically:

• Along the lower border of the subscapularis muscle

• Near the posterior axillary wall

• Accompanying the subscapular vessels (branches of the axillary artery and vein)

They typically number 6 to 7 nodes and lie deep to the skin and superficial fascia of the posterior axilla. These nodes send efferent lymphatic vessels to the central axillary nodes and eventually to the apical nodes at the apex of the axilla.

3. Structure

Like other lymph nodes, subscapular nodes are small, bean-shaped, and encapsulated, composed of specialized lymphoid tissue. Their key structural features include:

• Capsule: A dense connective tissue covering that gives rise to internal trabeculae

• Cortex: Contains lymphoid follicles rich in B cells

• Paracortex: Contains T cells and antigen-presenting dendritic cells

• Medulla: Composed of plasma cells, macrophages, and medullary sinuses

• Afferent vessels: Receive lymph from the skin and muscles of the posterior trunk and scapular region

• Efferent vessels: Drain into central axillary lymph nodes

4. Function

The subscapular axillary lymph nodes serve as an important immune filtration and relay station. Their primary functions include:

• Lymph filtration: Remove pathogens, debris, and abnormal cells from lymph originating in the back and shoulder regions

• Immune activation: Provide a site for antigen presentation to lymphocytes, initiating local immune responses

• Lymph transport: Act as a channel through which lymph is passed from superficial and deep posterior body regions to the central and apical nodes, and eventually to the subclavian lymph trunk

5. Physiological Role(s)

Subscapular nodes are integral to immune protection and lymphatic flow from the posterior upper body. Their physiological contributions include:

• Defense against skin and soft tissue infections: Especially those involving the scapula, posterior thorax, and upper limb base

• Maintaining tissue fluid homeostasis: Aid in preventing fluid accumulation by draining interstitial fluid from the back and axilla

• Surveillance of neoplastic cells: Detect and respond to early metastasis from nearby tissues, including breast and skin cancers

• Integration with axillary lymphatic chain: Function in concert with other axillary nodes (pectoral, humeral, central, and apical) to ensure complete upper limb and thoracic drainage

6. Clinical Significance

Lymphadenopathy

Enlargement of subscapular lymph nodes—called posterior axillary lymphadenopathy—can result from:

• Localized infections: Such as infected skin lesions, abscesses, or cellulitis of the back or scapular area

• Systemic infections: Including tuberculosis and viral infections (e.g., Epstein-Barr virus)

• Autoimmune diseases: Such as lupus or rheumatoid arthritis

Palpable swelling, tenderness, or restricted arm movement may signal pathology in this region.

Cancer Metastasis

Subscapular nodes are part of the lymphatic pathway for metastasis from:

• Breast cancer—especially tumors in the upper outer quadrant

• Melanoma or skin cancers of the back and shoulder

• Soft tissue sarcomas of the posterior thorax

Involvement of subscapular nodes can influence cancer staging (N-staging), treatment planning, and prognosis.

Axillary Lymph Node Dissection (ALND)

During surgical management of breast cancer, the subscapular group may be dissected as part of a Level I axillary lymph node dissection. Surgeons must carefully preserve surrounding neurovascular structures, including:

• Thoracodorsal nerve (innervates latissimus dorsi)

• Subscapular vessels

Lymphedema

Damage or surgical removal of subscapular nodes, especially in combination with other axillary nodes, may impair lymphatic return from the upper limb and back. This may lead to chronic axillary or upper limb lymphedema, requiring long-term physical therapy and compression management.

Imaging and Diagnosis

Subscapular nodes are not easily palpable due to their deep location, but may be assessed using:

• Ultrasound: To evaluate axillary nodal structure

• Mammography or breast MRI: May indirectly suggest involvement in breast cancer

• PET-CT or CT: To identify metabolically active or enlarged nodes in cancer staging

• Sentinel lymph node biopsy: May trace drainage into the subscapular group