Workup for Enlarged Axillary Lymph Node
Begin with axillary ultrasound as the primary imaging modality, followed by diagnostic mammography or digital breast tomosynthesis to evaluate the ipsilateral breast for occult malignancy. 1
Initial Imaging Approach
Axillary ultrasound is the first-line imaging test because it visualizes level I and II nodes, distinguishes solid from cystic masses, and assesses morphologic features such as cortical thickness, fatty hilum preservation, and vascularity patterns. 1
Diagnostic mammography and/or digital breast tomosynthesis should be performed concurrently to evaluate the ipsilateral breast for primary lesions, particularly since metastatic breast cancer is the most common malignant cause of axillary adenopathy even when the breast examination appears normal. 2, 1
Physical examination alone is inadequate for assessment, as both sensitivity and specificity are limited for detecting pathologic nodes. 1
Ultrasound-Guided Biopsy Indications
If ultrasound reveals suspicious features, proceed immediately to ultrasound-guided biopsy rather than delaying with observation, as this provides definitive diagnosis with high specificity (98-100%). 1
Suspicious ultrasound features include:
- Loss of fatty hilum
- Cortical thickening >3 mm
- Round rather than oval shape
- Abnormal vascularity patterns 1
Additional Workup Based on Initial Findings
If Biopsy Confirms Malignancy:
For metastatic adenocarcinoma with negative mammography: Obtain breast MRI, which identifies occult breast primary lesions in approximately 70% of cases. 2, 1
For lymphoma or non-breast malignancies: Proceed with CT chest/abdomen/pelvis or PET/CT for staging. 1, 3
For confirmed breast cancer metastasis: Complete breast imaging workup with diagnostic mammography/DBT and breast MRI. 1
If Initial Imaging is Benign-Appearing:
Consider clinical context carefully, as reactive lymphadenopathy from skin wounds, infections, or inflammatory conditions is common and benign. 1, 3
For nodes <1 cm with preserved fatty hilum: Short-term follow-up ultrasound at 6-8 weeks is reasonable if clinical suspicion is low. 4
For nodes ≥1 cm without fatty hilum infiltration: Biopsy is recommended regardless of benign appearance, as mammography cannot reliably distinguish benign from malignant enlargement. 5
Critical Pitfalls to Avoid
Do not rely on physical examination alone to determine if nodes are pathologic, as clinical assessment has poor sensitivity and specificity. 1
Do not delay biopsy of suspicious nodes based on size alone or hope that observation will clarify the diagnosis, as early diagnosis significantly impacts treatment planning and prognosis. 1
Do not use FDG-PET/CT as an initial imaging test for evaluating axillary lymphadenopathy, though it may be useful after malignancy is confirmed for staging purposes. 1, 3
Do not assume benign etiology without tissue diagnosis in nodes >1 cm lacking fatty hilum, even with negative breast imaging, as occult malignancies (breast cancer, lymphoma, melanoma) can present this way. 5, 6
Differential Diagnosis Considerations
The differential for enlarged axillary nodes includes:
Malignant causes:
- Metastatic breast cancer (most common malignant cause) 2, 3
- Lymphoma 2, 3
- Melanoma metastases 6
- Other metastatic malignancies 6, 7
Benign causes:
- Reactive lymphadenopathy from infection or inflammation 1, 3
- Autoimmune diseases 3
- Dermatologic conditions with skin breakdown 1
Clinical history regarding prior malignancy, recent infections, skin conditions, or systemic symptoms helps narrow the differential but does not replace tissue diagnosis for suspicious nodes. 6, 4