What is the next step in evaluating enlarged left axillary lymph nodes?

Evaluation of Enlarged Left Axillary Lymph Nodes

The next step in evaluating enlarged left axillary lymph nodes should be ultrasound of the axilla followed by ultrasound-guided fine needle aspiration (FNA) or core biopsy of suspicious nodes. 1

Initial Diagnostic Approach

• Ultrasound of the axilla is the primary modality of choice for initial evaluation of enlarged axillary lymph nodes, as it permits visualization of level I and II nodes and can determine if the mass is solid or cystic 1
• Diagnostic mammography and/or digital breast tomosynthesis (DBT) should complement axillary ultrasound to evaluate the ipsilateral breast for potential primary lesions, particularly when there is suspicion of breast cancer 1
• If ultrasound reveals suspicious lymph node features (loss of fatty hilum, cortical thickening, round shape, increased size), proceed with ultrasound-guided biopsy 1
• Ultrasound-guided FNA or core biopsy provides definitive diagnosis with high specificity (98-100%), though sensitivity can vary (52-90%) 1

Differential Diagnosis

Enlarged axillary lymph nodes may result from various etiologies:

• Malignant causes: breast cancer (most common), lymphoma, metastases from other primary sites 1, 2
• Benign causes: reactive adenopathy from infection, inflammatory processes, collagen vascular diseases 2
• Iatrogenic causes: recent COVID-19 vaccination (can persist up to 7 months) 3, silicone implants 4
• Infectious causes: bacterial or viral infections (including herpes zoster) 5

Further Evaluation Based on Initial Findings

If biopsy confirms malignancy:

• For confirmed breast cancer metastasis: complete breast imaging workup with diagnostic mammography/DBT and breast MRI 1
• For lymphoma or other non-breast malignancies: appropriate staging with CT chest/abdomen/pelvis or PET/CT 1

If biopsy is negative but clinical suspicion remains high:

• Consider surgical biopsy of the lymph node, particularly if >1 cm in size 6
• MRI of the breast may identify occult breast primaries in up to 70% of patients with axillary metastasis and negative mammogram 1

If occult breast cancer is suspected (axillary metastasis without identifiable breast primary):

• Breast MRI should be performed as it can identify the primary lesion in approximately 70% of cases 1
• For MRI-negative disease with biopsy-proven metastatic adenocarcinoma, treatment options include either mastectomy plus axillary nodal dissection or axillary nodal dissection plus whole-breast irradiation 1

Important Considerations

• Patients with enlarged lymph nodes often have benign reactive changes due to inflammation or infection of skin wounds, so clinical context is essential 1
• FDG-PET/CT is not recommended as an initial imaging test for evaluating axillary lymphadenopathy but may be useful in staging confirmed malignancy 1
• Sentinel lymph node biopsy may be considered in certain cases but should not replace initial ultrasound-guided biopsy when nodes appear suspicious 1
• Patients with a history of recent vaccination (particularly COVID-19) should be evaluated with this context in mind, as vaccine-related lymphadenopathy can persist for months 3

Pitfalls to Avoid

• Do not assume all enlarged axillary nodes represent metastatic breast cancer; the differential diagnosis is broad 2
• Do not rely solely on physical examination for assessment of axillary nodes as both sensitivity and specificity are limited 1
• Avoid delaying biopsy of suspicious nodes, as early diagnosis significantly impacts treatment planning and prognosis 1
• Be cautious about interpreting imaging findings without clinical context, as conditions like herpes zoster can mimic malignancy on imaging studies 5