Levels of Lymph Nodes
The lymph node levels are anatomically organized into specific regions, with Level I, II, and III in the axilla, internal mammary nodes, infraclavicular nodes, and supraclavicular nodes representing the primary classification system used in oncologic staging.
Axillary Lymph Node Levels
Level I (Low Axilla)
- Located lateral to the lateral border of the pectoralis minor muscle
- First echelon of lymphatic drainage from the breast
- Most commonly involved in breast cancer metastasis 1
Level II (Mid Axilla)
- Located deep to the pectoralis minor muscle
- Second echelon of lymphatic drainage
- Typically involved after Level I nodes in sequential spread pattern 1
Level III (Apical/Infraclavicular)
- Located medial to the medial border of the pectoralis minor muscle
- Also known as infraclavicular nodes
- Involvement indicates more advanced disease 1
Other Regional Lymph Node Groups
Internal Mammary Nodes
- Located in the parasternal region along the internal mammary vessels
- More commonly involved in medial and central breast tumors
- May be involved with or without axillary node involvement 1
Supraclavicular Nodes
- Located above the clavicle
- Involvement indicates advanced disease (classified as N3c)
- Associated with poorer prognosis 1
Neck Lymph Node Levels
In head and neck cancer staging, lymph nodes are categorized differently:
Submandibular Group
- Contains approximately 1-5 lymph nodes (mean 3.2)
- Perfused by branches of the facial artery 2
Upper Jugular Group
- Contains approximately 2-6 lymph nodes (mean 4.1)
- Perfused by the sternocleidomastoid artery 2
Clinical Significance
Prognostic Implications
- The number of involved nodes is a critical prognostic factor
- Micrometastases (>0.2 mm but ≤2.0 mm) have different implications than macrometastases (>2.0 mm)
- Extracapsular extension indicates more aggressive disease 1
Staging Classification
- pN1: 1-3 positive axillary nodes and/or internal mammary nodes with micrometastases
- pN2: 4-9 positive axillary nodes or clinically detected internal mammary nodes without axillary involvement
- pN3: ≥10 positive axillary nodes, infraclavicular nodes, internal mammary nodes with positive axillary nodes, or supraclavicular nodes 3, 1
Important Considerations
- Lymph node involvement typically follows a sequential pattern from Level I → Level II → Level III in breast cancer 1
- Most masses greater than 3 cm in diameter are not single lymph nodes but represent confluent nodes or tumor in soft tissues 3
- Histologic examination of a selective neck dissection specimen typically includes 6 or more lymph nodes, while radical or modified radical neck dissection specimens usually include 10 or more lymph nodes 3
Understanding lymph node levels is crucial for accurate staging, appropriate treatment planning, and determining prognosis in oncology patients.