What is the initial workup for a 2-year-old child presenting with an acute neck mass who is otherwise well?

Initial Workup for Acute Neck Mass in a 2-Year-Old Child

Ultrasound should be the first imaging modality for evaluation of an acute neck mass in an otherwise well 2-year-old child, as it differentiates solid from cystic lesions without radiation exposure. 1

Diagnostic Approach

Step 1: Clinical Assessment

• Evaluate key clinical features:
  • Duration of mass (acute onset vs. persistent)
  • Associated symptoms (fever, erythema, fluctuation)
  • Recent upper respiratory infection or trauma
  • Overlying skin changes
  • Size, location, and consistency of mass
  • Mobility or fixation to adjacent tissues

Step 2: Initial Imaging

• Ultrasound (US) of the neck is the preferred first-line imaging study 1, 2
  • Advantages:
    • No radiation exposure
    • No sedation required
    • Differentiates solid from cystic lesions
    • Can identify vascular malformations with color Doppler
    • Useful for evaluating superficial infections
    • Can guide FNA if needed

Step 3: Additional Imaging Based on US Findings

• If US suggests malignancy or deep neck infection requiring surgery:
  • CT neck with IV contrast should be performed 1
    • Advantages: Shorter examination time, reduced/absent sedation requirements
    • Use ALARA (As Low As Reasonably Achievable) radiation protocols
  • MRI neck without and with IV contrast is an alternative 1
    • Preferred for suspected malignancy requiring detailed soft tissue evaluation
    • May require sedation in young children

Differential Diagnosis by Category

1. Inflammatory/Infectious (most common in children) 2, 3

   • Reactive lymphadenopathy
   • Bacterial lymphadenitis (Staphylococcus aureus, Group A Streptococcus)
   • Viral lymphadenitis
   • Deep neck abscess

2. Congenital/Developmental 2, 3

   • Thyroglossal duct cyst
   • Branchial cleft cyst
   • Dermoid cyst
   • Lymphangioma/cystic hygroma
   • Hemangioma
   • Vascular malformations

3. Neoplastic (rare in children but must be considered) 2, 4

   • Lymphoma
   • Neuroblastoma
   • Rhabdomyosarcoma
   • Thyroid carcinoma

Laboratory Testing

If infectious etiology is suspected, consider:

• Complete blood count
• Blood culture if febrile
• Specific serologic tests based on clinical suspicion (EBV, CMV, toxoplasmosis) 2

Management Algorithm

1. For suspected infectious etiology with typical presentation:

   • Consider empiric antibiotic therapy targeting S. aureus and Group A Streptococcus
   • Reassess within 2 weeks
   • If no resolution or only partial resolution, proceed with imaging workup

2. For non-infectious appearing mass:

   • Proceed directly to ultrasound
   • Follow imaging pathway based on ultrasound findings

3. Red flags requiring urgent evaluation:

   • Fixed mass
   • Firm/hard consistency
   • Size >2 cm
   • Ulceration of overlying skin
   • Persistent enlargement >2 weeks
   • Supraclavicular location
   • Absence of inflammatory signs
   • Failure to respond to appropriate antibiotics

Important Considerations

• Neck masses in children are most commonly inflammatory or congenital rather than neoplastic 2, 5
• The American College of Radiology recommends that CT and MRI studies may be complementary to ultrasound in pediatric neck masses 1
• Avoid unnecessary radiation exposure in children by using ultrasound as the first imaging modality
• Malignant etiologies are less frequent in children compared to adults, but awareness of this potential is important 3

Remember that the diagnostic approach should be guided by clinical findings, with ultrasound as the initial imaging study for an acute neck mass in an otherwise well child.