What are the anatomic boundaries of the various nodal stations used in lung cancer staging?

Anatomic Boundaries of Lung Cancer Nodal Stations

The International Association for the Study of Lung Cancer (IASLC) lymph node map defines 14 nodal stations organized into 7 zones, with specific anatomic boundaries that are essential for accurate lung cancer staging. 1

Key Anatomic Boundaries by Station

Supraclavicular Zone

• Station 1: Low cervical, supraclavicular, and sternal notch nodes
  • Extends from the lower border of the cricoid cartilage (superior) to the lower border of the clavicles (inferior) 1

Upper Zone (Stations 2-4)

Station 2 (Upper Paratracheal)

• Extends from the upper border of the manubrium (superior) to the border with station 4 (inferior) 1

Station 4R (Right Lower Paratracheal)

• Superior boundary: Lower border of the left innominate vein
• Inferior boundary: Lower border of the azygous vein 1

Station 4L (Left Lower Paratracheal)

• Superior boundary: Level of the top of the aortic arch
• Inferior boundary: Upper border of the left pulmonary artery medial to the ligamentum arteriosum 1

Critical Distinction: The border between right and left paratracheal nodes is the left lateral border of the trachea (NOT the midline) 1

Aortopulmonary Zone (Stations 5 and 6)

• Station 5: Subaortic (aortopulmonary window) nodes
• Station 6: Para-aortic nodes
• These stations are particularly important for left upper lobe tumors 2

Subcarinal Zone

• Station 7: Subcarinal nodes
  • Extends down to the level of origin of the left lower lobe bronchus and right middle lobe bronchus 1
  • This represents a key update in the IASLC map with better anatomic definition

Lower Zone (Stations 8 and 9)

• Station 8: Paraesophageal nodes
• Station 9: Pulmonary ligament nodes

Hilar Zone (Stations 10 and 11)

• Station 10: Hilar nodes (main bronchus nodes)
• Station 11: Interlobar nodes

Peripheral Zone (Stations 12-14)

• Station 12: Lobar nodes
• Station 13: Segmental nodes
• Station 14: Subsegmental nodes 1

Clinical Staging Implications

The IASLC map reconciled previous discrepancies between Asian and Western lymph node maps to create international uniformity 3. The number of involved nodal zones has prognostic significance: patients with single-zone N2 involvement have better 5-year survival (34%) compared to multizone N2 involvement (20%, P < .001) 1.

Important Pitfalls to Avoid

1. Do not use the midline to separate right and left paratracheal nodes—use the left lateral tracheal border 1

2. Station 1 nodes are N3 (supraclavicular), not N2, despite being regional nodes 1

3. Direct tumor extension into a lymph node is classified as nodal involvement, not primary tumor extension 1

4. For pathologic staging, sample at least 3 mediastinal stations (including station 7) and 3 N1 stations 1

The IASLC map provides CT-based illustrations for clinical application, making it practical for day-to-day radiologic staging 4. This standardized system is now incorporated into the TNM classification and is essential for treatment planning, particularly when determining surgical resectability and radiation field design.