Lymphatic Drainage of Breast

The lymphatic drainage of the breast is a critical anatomical and clinical consideration due to its direct involvement in the spread of breast cancer, infections, and immune responses. The lymphatic network is extensive and drains both the superficial skin and the deeper parenchymal tissues of the breast. The system is organized into two major components: superficial lymphatics and deep (parenchymal) lymphatics, both of which drain toward regional lymph nodes, particularly the axillary group.

Superficial Lymphatic System

The superficial lymphatics are responsible for draining the skin of the breast, excluding the nipple and areola. These vessels form a subdermal plexus and follow routes toward regional nodes:

• Lateral and superior skin: Drains into the axillary lymph nodes

• Medial skin: May drain into parasternal lymph nodes along the internal thoracic vessels

• Inferior skin: May have drainage to subdiaphragmatic and upper abdominal nodes, including subperitoneal lymphatics

There is extensive communication between the superficial lymphatics of both breasts across the midline, particularly near the sternum. This allows for potential bilateral spread of pathology, especially in cases of malignancy or mastitis.

Deep (Parenchymal) Lymphatic System

The deep lymphatics drain the glandular tissue, ducts, and nipple-areolar complex. These vessels converge primarily toward the base of each lobe and lobule and ultimately toward the following nodal groups:

• Axillary lymph nodes: Receive 75–85% of deep breast lymph drainage

• Parasternal (internal mammary) lymph nodes: Drain medial and deep portions of the breast

• Interpectoral (Rotter’s) lymph nodes: Located between pectoralis major and minor; serve as an intermediate station between breast and axillary nodes

• Posterior intercostal nodes: May receive lymph from the posterior portion of the breast

Lymphatic Drainage of the Nipple and Areola

The nipple and areola have dense lymphatic networks that drain centrally into the subareolar lymphatic plexus (Sappey’s plexus). This plexus is considered the convergence point for both superficial and deep lymphatic systems and directs lymph into axillary, parasternal, and infraclavicular nodes.

Axillary Lymph Node Groups

These nodes are divided into several anatomical levels and groups:

• Anterior (pectoral) group: Receives lymph from most of the anterior thoracic wall and lateral breast

• Central group: Deep within the axilla; receives lymph from pectoral, subscapular, and humeral groups

• Posterior (subscapular) group: Receives lymph from posterior thoracic wall and scapular region

• Lateral (humeral) group: Related mainly to upper limb drainage

• Apical group: Located at the apex of the axilla; receives lymph from all other axillary nodes and drains into the subclavian lymph trunk

In oncological practice, axillary nodes are further categorized by Level I, II, and III:

• Level I: Nodes lateral to the pectoralis minor

• Level II: Nodes posterior to the pectoralis minor (including Rotter’s nodes)

• Level III: Nodes medial to the pectoralis minor (apical group)

Parasternal (Internal Mammary) Nodes

These lie along the internal thoracic vessels, just lateral to the sternum, and receive lymph from the medial breast. They form an important pathway for the contralateral spread of cancer and are often involved in medial tumors. Lymph from these nodes drains into the bronchomediastinal trunks.

Clinical Relevance

• Breast cancer staging: Sentinel lymph node biopsy often targets the first axillary node draining the tumor area, commonly located in the pectoral group

• Contralateral spread: Medial tumors may cross to the opposite parasternal lymph nodes, leading to bilateral involvement

• Lymphedema risk: Axillary node removal or radiation can impair lymphatic drainage, leading to swelling of the upper limb and chest wall

• Inflammatory conditions: Infections such as mastitis or abscesses often present with regional lymphadenopathy

The lymphatic anatomy of the breast is complex and clinically significant. Accurate knowledge of these drainage routes is essential in oncologic planning, surgical intervention, and radiologic interpretation.