Normal Lymph Node Size and Evaluation Thresholds
Lymph nodes measuring <10 mm in short-axis diameter are considered normal, while those >15 mm in short-axis diameter require further workup for potential malignancy. 1
Size Thresholds by Location
The definition of normal lymph node size varies by anatomic location, with specific thresholds established for different regions:
General Mediastinal and Thoracic Nodes
- Normal size: Short-axis diameter <10 mm 2
- Abnormal/requires evaluation: Short-axis diameter ≥10 mm 2
- Highly suspicious: Long-axis diameter >15 mm 2
- Nodes measuring 10-14 mm are considered abnormal but should not be selected as target lesions in lymphoma staging 2
Abdominal and Retroperitoneal Nodes
Normal size thresholds vary significantly by specific location 3:
- Retrocrural space: ≤6 mm
- Paracardiac region: ≤8 mm
- Gastrohepatic ligament: ≤8 mm
- Upper paraaortic region: ≤9 mm
- Portacaval space: ≤10 mm
- Porta hepatis: ≤7 mm
- Lower paraaortic region: ≤11 mm 3
Cervical Lymph Nodes
- Normal size: <10 mm short-axis diameter 4
- Requires assessment: ≥10 mm 4
- Suspicious for malignancy: >15 mm 1, 4
Testicular Cancer Staging (Retroperitoneal)
- Normal: <10 mm short-axis diameter 2
- Highly suspicious: >10 mm in short axis, particularly in para-aortic or paracaval regions 2
- Important caveat: Up to 60% of metastatic lymph nodes may be <10 mm, so some experts suggest using 7-8 mm cutoff in testicular cancer at the expense of reduced specificity 2
Clinical Decision Algorithm Based on Size
Nodes <10 mm
- Generally considered benign if no concerning morphologic features present 1
- No further workup typically needed in asymptomatic patients 1
- Exception: In testicular cancer, nodes 7-8 mm may warrant closer surveillance 2
Nodes 10-15 mm
- Considered abnormal but borderline 2
- Require clinical correlation with patient history, symptoms, and risk factors 1
- Consider follow-up imaging with CT or PET/CT 1
- In lymphoma staging, nodes 11-15 mm with long axis <15 mm should not be selected as target lesions 2
Nodes 15-25 mm
- Require further evaluation, especially if other concerning features present 1
- Consider follow-up imaging with CT or PET/CT 1
- In lymphoma, nodes ≥15 mm in long-axis diameter can be considered target lesions 2
Nodes >25 mm
- Highly suspicious for pathology and require immediate workup 1
- Biopsy (FNA, core needle, or excisional) often indicated 1
Critical Morphologic Features Beyond Size
Size alone is insufficient for determining clinical significance. Evaluate these additional features 1, 5:
Benign Features
- Preserved fatty hilum (most reassuring sign) 1, 5
- Smooth, well-defined borders 1, 5
- Homogeneous echogenicity/attenuation 4, 5
- Oval shape (wider than tall) 1
Concerning Features Suggesting Malignancy
- Loss of fatty hilum 1
- Round shape (independently predictive of malignancy) 1
- Distinct margins with heterogeneous echogenicity 1
- Central necrosis (strongly suggests malignancy) 1
- Increased vascularity with multiple vessels on Doppler 1
Common Pitfalls and Caveats
Critical limitation: Ultrasonographic and CT features are not reliable enough to forgo biopsy for definitive diagnosis when malignancy is suspected 1
Non-malignant causes of enlarged nodes: Lymph nodes >10 mm can be associated with infections, heart failure, and granulomatous diseases 1
Context matters: In patients with known malignancy, different criteria may apply according to specific cancer types 1
Young males with mediastinal lymphadenopathy: Consider lymphoma, seminoma, and non-seminomatous germ cell tumors 1
Measurement technique: Short-axis diameter shows less variation and is more reliable than long-axis diameter for determining abnormality 2, 6