How to differentiate between malignant and infective lymphadenopathy in a child using ultrasound (USG)?

Differentiating Malignant and Infective Lymphadenopathy in Children Using Ultrasound

Specific ultrasonographic features can help differentiate between malignant and infective lymphadenopathy in children, with round shape, distinct margins, heterogeneous echogenicity, and central necrosis being independently predictive of malignancy, though tissue sampling remains necessary for definitive diagnosis. 1, 2

Key Ultrasonographic Features

Features Suggestive of Malignancy

• Shape: Round nodes are more likely malignant than oval/triangular nodes 1
• Margins: Distinct, well-defined borders 1
• Internal Architecture:
  • Heterogeneous echogenicity 1, 2
  • Central necrosis sign 1
  • Loss of fatty hilum 2
• Vascularity: Increased blood flow (grade 2-3) with multiple vessels (>4) 1
  • Sensitivity of 87.7% and specificity of 69.6% for malignancy 1
• Size: While findings are conflicting, larger nodes may have higher likelihood of malignancy 1

Features Suggestive of Benign/Infective Process

• Shape: Oval with longitudinal-transverse (L/T) ratio >2 3
• Internal Architecture:
  • Homogeneous echogenicity 1
  • Presence of central hilar structure 1
• Vascularity: No blood flow (grade 0) or single central vessel (grade 1) 1
• Specific Infection Patterns:
  • Tuberculosis: Coagulation necrosis and heterogeneous echogenicity 1
  • Reactive nodes: Preservation of hilar architecture and proper vascularization 4

Diagnostic Algorithm

1. Initial Assessment:

   • Measure size: Short-axis diameter >1.0 cm is considered abnormal 2
   • Evaluate shape: Oval vs. round
   • Assess margins: Distinct vs. indistinct

2. Internal Structure Evaluation:

   • Check for presence/absence of fatty hilum
   • Evaluate echogenicity (homogeneous vs. heterogeneous)
   • Look for central necrosis

3. Vascular Assessment (using Doppler):

   • Grade 0: No blood flow
   • Grade 1: Single central vessel (likely benign)
   • Grade 2-3: Rich flow with >4 vessels (concerning for malignancy)

4. Combined Feature Analysis:

   • When all four malignant features are absent (round shape, distinct margins, heterogeneous echogenicity, central necrosis), 96% of lymph nodes are benign 1
   • Presence of multiple malignant features increases likelihood of malignancy

Important Considerations

• Limitations: Ultrasonographic predictors of malignancy are not reliable enough to forgo biopsy for definitive diagnosis 1, 2
• Follow-up: Failure of regression after 4-6 weeks of appropriate treatment might indicate need for diagnostic biopsy 4
• Additional Imaging: Consider cross-sectional imaging (preferably MRI) if suspicious features are detected on ultrasound 2
• Clinical Context: Consider patient's symptoms, history of malignancy, and clinical presentation alongside ultrasonographic findings 2

Pitfalls and Caveats

• Size alone is not a reliable indicator of malignancy, as studies show conflicting results 1
• Some malignant features (like heterogeneous echogenicity) can also be present in certain infections like tuberculosis 1
• Point-of-care ultrasound should describe shape, size, internal echotexture, borders, vascularity, and perinodal soft tissue patterns for comprehensive evaluation 5
• Ultrasound has limitations in providing definitive diagnosis of lymphoma and its tissue characterization capability is inferior to MRI 2

While ultrasound features can guide clinical decision-making, tissue sampling remains essential for definitive diagnosis in cases with persistent or concerning features.