What is the first test to confirm the presence of lymph nodes in a patient with suspected lymphadenopathy in the neck and mediastinum?

First Test for Suspected Lymphadenopathy in Neck and Mediastinum

Ultrasound of the neck is the first imaging test for evaluating suspected cervical lymphadenopathy, while contrast-enhanced CT of the chest is the initial test for mediastinal lymph node assessment. 1, 2

Cervical (Neck) Lymph Node Evaluation

Begin with neck ultrasound as the primary imaging modality for suspected cervical lymphadenopathy, as it can characterize palpable abnormalities and detect deeper neck masses that are not palpable. 1

Key advantages of neck ultrasound:

• Superior specificity (92%) compared to CT (25%) for cervical nodes, with similar sensitivity (75% for US vs 80% for CT). 1
• Can guide subsequent tissue sampling if abnormalities are detected. 2
• Non-invasive and readily available as first-line imaging. 1

When to add CT neck:

• CT neck with contrast complements ultrasound for detecting additional metastases in the central compartment, mediastinum, and retrotracheal areas. 1
• Use CT when ultrasound findings are equivocal or when deeper structures need evaluation. 1

Mediastinal Lymph Node Evaluation

Contrast-enhanced CT of the chest is the initial imaging test for mediastinal lymphadenopathy. 1, 2

CT chest protocol specifics:

• Always use intravenous contrast to better assess for tumor vascular encasement and small nodal metastases with hyperenhancement and necrosis. 1
• Dual-phase CT (with and without contrast) provides no additional information and is unnecessary. 1

Size-based interpretation for mediastinal nodes:

• Nodes <15mm in asymptomatic patients require no further workup. 2
• Nodes 15-25mm need clinical correlation with consideration of follow-up imaging at 3 months if explainable by benign conditions (emphysema, interstitial lung disease, cardiac disease). 2
• Nodes >25mm are always pathologic and require tissue diagnosis. 2

When to Proceed Beyond Initial Imaging

Add PET-CT in specific scenarios:

• High clinical suspicion despite normal or equivocal CT findings. 1
• Young males with mediastinal lymphadenopathy (consider lymphoma, seminoma, or germ cell tumors). 2
• Presence of B symptoms (fever, night sweats, weight loss) regardless of node size. 2
• PET has approximately 77% sensitivity and 86% specificity for mediastinal metastasis, superior to CT alone. 1

Tissue diagnosis algorithm:

• For discrete enlarged nodes or PET-avid nodes, use EBUS-NA or EUS-NA as first-line tissue sampling rather than surgical staging. 1, 2
• EBUS-NA has 93% sensitivity and 100% specificity; EUS-NA has 92-97% sensitivity and 100% specificity. 2
• If needle techniques are negative but clinical suspicion remains high, proceed to surgical staging (mediastinoscopy, VATS). 1

Critical Pitfalls to Avoid

• Never rely on size alone: Normal-sized nodes can harbor microscopic metastases in 20-25% of patients with central tumors. 2
• Do not assume malignancy in patients with cancer history: Benign causes (inflammation, sarcoidosis) occur in 40% of patients with prior extrathoracic malignancy. 2
• Never accept negative needle biopsy as definitive when clinical suspicion is high: Surgical staging should follow. 1, 2
• Avoid starting antibiotics or corticosteroids empirically: Corticosteroids can mask histologic diagnosis of lymphoma or malignancy. 3

Special Considerations

For thyroid-related lymphadenopathy:

• Ultrasound remains the first test for thyroid bed and cervical node evaluation in suspected thyroid cancer recurrence. 1

For lung cancer staging:

• In patients with high suspicion of N2,3 involvement (discrete mediastinal lymph node enlargement or PET uptake), needle techniques (EBUS-NA, EUS-NA) are recommended over surgical staging as the best first test. 1
• Invasive staging is recommended over imaging alone when discrete mediastinal lymph node enlargement is present. 1