What laboratory tests should be ordered for a patient presenting with a neck lump?

Laboratory Testing for Neck Lumps in Adults

Laboratory tests for neck lumps should be ordered selectively based on clinical suspicion from history and physical examination, not routinely for all patients. 1

Risk-Stratified Approach to Laboratory Testing

The American Academy of Otolaryngology-Head and Neck Surgery emphasizes that ancillary laboratory tests should only be obtained when clinical suspicion exists for specific diseases, and these tests are most useful when combined with imaging and fine-needle aspiration (FNA) results. 1

First-Line Laboratory Tests (Based on Clinical Suspicion)

Complete Blood Count (CBC) with Differential should be ordered when:

• Infection is suspected (elevated WBC suggests bacterial infection or lymphoma) 1
• Immunosuppression is a concern (depressed WBC) 1
• Lymphoma is in the differential diagnosis 1

Thyroid-Stimulating Hormone (TSH) should be ordered when:

• The mass appears to arise from or involve the thyroid gland 1
• Elevated TSH suggests toxic multinodular goiter 1
• Decreased TSH suggests Hashimoto's thyroiditis or Graves' disease 1

Infection-Related Testing

HIV enzyme-linked assay should be ordered when:

• Risk factors for HIV are present 1
• Persistent lymphadenopathy without clear etiology exists 1

Epstein-Barr Virus (EBV) antibody titers should be ordered when:

• Clinical features suggest infectious mononucleosis 1
• Nasopharyngeal carcinoma is suspected (EBV-associated) 1

Mantoux tuberculin test (PPD) should be ordered when:

• Tuberculosis is suspected based on risk factors or presentation 1
• Elevated ESR accompanies the neck mass 2

CMV IgM titer should be ordered when:

• CMV infection is clinically suspected 1

Bartonella titer should be ordered when:

• Cat-scratch disease is suspected (history of cat exposure) 1

Autoimmune/Inflammatory Testing

Erythrocyte Sedimentation Rate (ESR) should be ordered when:

• Autoimmune disease is suspected 1
• Tuberculosis is in the differential (markedly elevated ESR with anterior neck mass suggests TB) 2
• Systemic inflammation markers are needed 1

Antinuclear Antibody (ANA); anti-Ro/SSA, anti-La/SSB should be ordered when:

• Sjögren's syndrome is suspected 1
• Systemic lupus erythematosus (SLE) is suspected 1

Specialized Testing for Thyroid/Parathyroid Masses

Parathyroid Hormone (PTH) should be ordered when:

• Parathyroid adenoma, hyperplasia, or carcinoma is suspected 1

Thyroglobulin FNA-needle wash assay should be ordered when:

• FNA is performed on a suspected thyroid cancer metastasis to cervical lymph nodes 1
• This test has high diagnostic accuracy for detecting neck recurrences from differentiated thyroid cancer 3, 4

Critical Timing Considerations

For patients at increased risk for malignancy, ancillary testing must be performed simultaneously with the malignancy workup to avoid delayed cancer diagnosis. 1

High-risk features requiring urgent evaluation include:

• Mass present ≥2 weeks without fluctuation 5
• Firm, fixed consistency 5
• Size >1.5 cm 5
• History of smoking, alcohol use, or prior head/neck radiation 5
• Constitutional symptoms (weight loss) 5
• Voice changes, dysphagia, or persistent sore throat 5

Common Pitfalls to Avoid

• Do not order a "shotgun" panel of tests without clinical suspicion for specific diseases, as this is not recommended and delays diagnosis 1
• Do not delay imaging and FNA while waiting for laboratory results in high-risk patients 1
• Do not assume normal inflammatory markers exclude malignancy, as ESR and CRP have limited value in distinguishing benign from malignant thyroid disease 6
• Do not prescribe antibiotics without clear evidence of infection while awaiting test results 7, 5