What blood tests should be ordered for a patient presenting with a lump in the axilla (armpit)?

Blood Tests for Axillary Lump Evaluation

Ultrasound of the axilla should be performed as the first-line diagnostic test for a patient presenting with a lump in the armpit, followed by appropriate blood tests based on clinical suspicion. 1, 2

Initial Diagnostic Approach

Imaging First

• Ultrasound of the axilla: First-line imaging modality for all patients with an axillary lump 1, 2
• For patients ≥30 years: Add diagnostic mammography or digital breast tomosynthesis 2
• For patients <30 years: Ultrasound only (no mammography) 2

Blood Tests Based on Clinical Context

After imaging, the following blood tests should be ordered based on clinical suspicion:

1. Basic Laboratory Evaluation:

   • Complete Blood Count (CBC) with differential 1
     • Evaluates for infection (elevated WBC)
     • Screens for hematologic malignancies (abnormal cell counts)
     • Assesses for anemia or other blood disorders

2. Additional Tests Based on Clinical Suspicion:

   • If infection is suspected:

     • C-Reactive Protein (CRP) 1
     • Erythrocyte Sedimentation Rate (ESR) 1

   • If autoimmune disease is suspected:

     • Antinuclear Antibody (ANA) 1
     • Anti-Ro/SSA, Anti-La/SSB antibodies 1

   • If thyroid pathology is suspected:

     • Thyroid-Stimulating Hormone (TSH) 1

   • If kidney cancer with metastasis is suspected:

     • Comprehensive metabolic panel 1
     • Serum calcium
     • Liver function tests
     • Lactate dehydrogenase (LDH)
     • Serum creatinine

Diagnostic Algorithm

1. Initial Assessment:

   • Perform axillary ultrasound for all patients 1, 2
   • Order CBC with differential as baseline blood test 1

2. Based on Ultrasound Findings:

   • Normal lymph nodes: Monitor clinically
   • Suspicious lymph nodes: Proceed to ultrasound-guided biopsy 1
   • Indeterminate findings: Order additional blood tests based on clinical suspicion

3. Additional Testing Based on Clinical Features:

   • Fever, redness, warmth: Add CRP, ESR (infection markers) 1
   • Joint pain, rash, dry eyes/mouth: Add ANA, Anti-Ro/SSA, Anti-La/SSB (autoimmune markers) 1
   • Neck swelling, weight changes: Add TSH (thyroid assessment) 1
   • Constitutional symptoms (weight loss, fatigue): Add comprehensive metabolic panel 1

Important Considerations

• Blood tests alone cannot diagnose the cause of an axillary lump but can guide further management
• Ultrasound-guided biopsy is superior to fine needle aspiration for diagnosis of suspicious lymph nodes 1
• For patients with suspected malignancy, additional imaging of potential primary sites may be necessary 1
• If initial blood tests and imaging are inconclusive, consider examination under anesthesia of the upper aerodigestive tract before open biopsy 1

Common Pitfalls to Avoid

• Relying solely on blood tests without imaging
• Failing to perform breast imaging when axillary lymphadenopathy is present 2
• Missing non-breast etiologies such as systemic diseases, lymphoma, and other malignancies 2
• Delaying biopsy when imaging findings are suspicious, regardless of blood test results

Remember that while blood tests provide valuable information, the diagnostic approach to an axillary lump requires correlation with imaging findings and possibly tissue sampling for definitive diagnosis.