What are hilar lymph nodes, where are they located, how are they visualized on imaging, and what is the recommended evaluation and management of their enlargement?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: February 14, 2026 • View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

Hilar Lymph Nodes of the Lung: Anatomy, Imaging, and Clinical Evaluation

Anatomical Location and Definition

Hilar lymph nodes are located at the lung hilum where the main bronchi, pulmonary arteries, and pulmonary veins enter and exit the lung parenchyma. 1

  • Right hilar nodes are positioned lateral to the A2 bronchus (79% of cases), medial or lateral to the interlobar pulmonary artery, and medial to the lower-lobe pulmonary artery 2

  • Left hilar nodes are found lateral to the A2 bronchus (49% of cases), medial to the interlobar pulmonary artery (100% of cases), medial to the lower-lobe pulmonary artery (60%), and in the angles of bifurcation of segmental arteries 2

  • Normal hilar lymph nodes appear triangular or linear and measure less than 3 mm in width on spiral CT, except around the left lower-lobe pulmonary artery where they may be slightly larger 2

  • In the TNM staging system, hilar nodes are classified as N1 nodes (stations 10-13: hilar, interlobar, lobar, segmental, and subsegmental) 1

Imaging Visualization

CT Imaging (Primary Modality)

CT with thin-section technique (1-3 mm slices) is the imaging method of choice for visualizing hilar lymph nodes. 1

  • Size criteria: Nodes with short-axis diameter >10 mm are considered abnormal, though the traditional threshold is 14 mm 1

  • Morphologic criteria significantly improve diagnostic accuracy beyond size alone 1

    • Convex pleural interface between hilar structures and lung parenchyma indicates malignant involvement (95% specificity) 1
    • Straight or concave pleural interface suggests normal lymph nodes (95% specificity) 1
    • This morphologic criterion improves sensitivity from 50% to 87% and specificity from 80% to 83% 1

  • Multidetector CT with coronal reformations provides superior visualization of hilar anatomy and lymph node relationships 1

PET-CT Imaging

PET-CT is more accurate than CT alone for detecting hilar and mediastinal lymph node metastases, with median sensitivity of 80% and specificity of 88%. 1

  • PET relies on metabolic activity rather than anatomical size, allowing detection of malignancy in normal-sized nodes 1

  • Integrated PET-CT scanning is superior to visual correlation of separate PET and CT images for distinguishing hilar from mediastinal nodes 1

  • Limitation: PET is less sensitive for lymph nodes <7-10 mm in diameter due to spatial resolution constraints 1

MRI Imaging

MRI can visualize hilar lymph nodes approximately 1 cm in diameter that may be difficult to appreciate on CT. 3

  • MRI differentiates hilar masses from vasculature more easily than contrast-enhanced CT 3

  • Short inversion time inversion-recovery (STIR) sequences demonstrate high diagnostic accuracy (84-96%) for hilar node assessment 1

  • Diffusion-weighted imaging (DWI) shows promise with accuracy up to 98% for detecting nodal metastases 1

  • MRI is reserved for problem-solving when CT findings are equivocal, not for routine evaluation 1

Endobronchial Ultrasound (EBUS)

EBUS provides real-time visualization of hilar lymph nodes and enables ultrasound-guided transbronchial needle aspiration (TBNA). 4, 5

  • EBUS measurements of hilar nodes show weak correlation with CT measurements (intraclass correlation 0.44) 5

  • Benign nodes measure larger on CT than EBUS (14.1 mm vs 11.5 mm), while malignant nodes measure larger on EBUS than CT (17.3 mm vs 16.2 mm) 5

  • Critical finding: 24% of lymph nodes initially interpreted as normal-sized on axial CT contained malignant cells when sampled by EBUS-TBNA 5

Evaluation of Enlarged Hilar Lymph Nodes

Initial Assessment

When hilar lymph nodes are enlarged on CT or PET-CT, tissue confirmation is mandatory before denying potentially curative surgery. 1

  • Do not rely on size alone: Normal-sized nodes can harbor microscopic metastases, and enlarged nodes may be hyperplastic rather than neoplastic 1, 6

  • CT has limited sensitivity (41-67%) and specificity (79-86%) for determining nodal status based on size criteria alone 1

Diagnostic Algorithm for Hilar Node Enlargement

For peripheral tumors with enlarged hilar nodes on imaging, proceed with endosonography (EBUS/EUS) as the first-line invasive staging procedure. 1

  1. If endosonography is positive: Confirms N1 disease; proceed with appropriate treatment planning 1

  2. If endosonography is negative: Proceed to surgical staging (mediastinoscopy with complete nodal dissection) to avoid false-negative results 1

  3. Combined EBUS/EUS approach achieves 93% sensitivity, superior to either modality alone (69% each) 1

For central tumors or tumors >3 cm, invasive staging should be considered even with normal-sized nodes on imaging. 1

Key Diagnostic Pitfalls

  • False-positive imaging results occur with benign reactive nodes showing follicular hyperplasia, which can appear enlarged but contain few macrophages 1, 6

  • False-negative imaging results occur when microscopic metastases exist within normal-sized lymph nodes 1

  • 65% of lymph nodes initially interpreted as not enlarged on axial CT actually measured >10 mm on coronal CT and EBUS 5

  • Enlarged lymph nodes seen on CT must be sampled with biopsy to avoid overstaging before denying surgery 1

Tissue Sampling Recommendations

EBUS-TBNA is the preferred minimally invasive procedure for accessible hilar lymph nodes. 1, 4

  • EBUS-TBNA is safe with few complications and provides real-time guidance for needle placement 4

  • If EBUS-TBNA is negative in the presence of suspicious imaging findings, confirm with surgical staging (mediastinoscopy or video-assisted mediastinotomy) 1

  • For nodes in stations 5 and 6 (aortopulmonary window), EBUS cannot access these locations; left anterior mediastinotomy or VATS is required 1

Special Considerations

  • In patients with small peripheral tumors (T1a) and normal-sized, PET-negative hilar nodes, the risk of occult N1 disease is low but not zero 1

  • For adenocarcinomas with high FDG uptake and tumors >3 cm, invasive staging should be considered even with normal imaging 1

  • Post-treatment evaluation: CT remains the procedure of choice for routine follow-up; filling-in of previously patent ectatic bronchi may indicate recurrence 1

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

6
Guideline

Differential Diagnosis for Enlarged Lymph Nodes

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

Related Questions

Where is the left hilar (lymph node) located in a typical adult patient?
Is it easy to biopsy hilar lymph nodes in patients with suspected malignancy or granulomatous disease, such as sarcoidosis?
What does a vascular hilar soft tissue density mean?
What is the recommended treatment for a patient with a large hilar mass and necrotic lymph nodes causing pulmonary artery and bronchus compression of the right upper lobe with associated opacities?
What is the differential diagnosis of right hilum enhancement on a chest x-ray?
What is the most appropriate treatment—mannitol, hyperventilation, or craniotomy—for a patient who was initially conscious, then became unresponsive, was intubated prehospital, and whose post‑resuscitation CT shows an acute convex (extradural or acute subdural) hematoma?
In an adult with normal renal function, how long should apixaban be held after thoracentesis before restarting?
What is the most appropriate initial treatment for a 45-year-old patient with an acute posterior midline anal fissure and increased internal sphincter tone?
How can constipation be prevented or treated during fasting?
Will radiation to the hilar lymph nodes cause throat pain?
Can radiation to a mediastinal lymph node cause throat pain (sore throat/odynophagia)?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question