Lymph Node vs Cyst: Physical Examination Differences
Lymph nodes and cysts feel distinctly different on palpation, with lymph nodes typically being firm, mobile, and discrete, while cysts are usually fluctuant, smooth-walled, and may transmit light.
Key Distinguishing Features
Lymph Nodes
- Consistency: Firm, rubbery texture
- Mobility: Usually mobile when palpated
- Shape: Oval or round with discrete edges
- Tenderness: May be tender if inflamed
- Location: Found in predictable anatomical locations (neck, axilla, groin)
- Multiple vs. Solitary: Often found in groups
- Surface: Smooth but firm surface
Cysts
- Consistency: Fluctuant, fluid-filled sensation
- Mobility: Mobile within tissue planes
- Shape: Round with smooth borders
- Transillumination: May transmit light (especially clear cysts)
- Compression: Can sometimes be compressed
- Wall characteristics: Smooth, well-defined wall
- Fluctuation: Demonstrates fluctuation when palpated from different angles
Important Clinical Considerations
Concerning Features for Lymph Nodes
- Fixed/immobile nodes
- Hard consistency
- Rapidly enlarging
- Size >2 cm
- Persistent enlargement >6 weeks
- Absence of local infection
- Supraclavicular location
- Associated constitutional symptoms
Concerning Features for Cysts
- Asymmetric wall thickness
- Areas of nodularity
- Nonconforming cystic wall
- Rapid growth
- Pain or tenderness
Diagnostic Pitfalls
Cystic metastatic lymph nodes: Certain cancers (especially papillary thyroid carcinoma and squamous cell carcinoma) can present as cystic lymph nodes, mimicking benign cysts 1.
Malignant cystic masses: Up to 80% of cystic neck masses in patients over 40 years may be malignant 2.
False reassurance: Cystic masses should not be automatically assumed benign, as they may represent malignancy, especially in adults 2.
Diagnostic challenges: Fine-needle aspiration of cystic metastases has higher false-negative rates (73% sensitivity) compared to solid masses (90% sensitivity) 2.
When to Pursue Further Evaluation
- Persistent mass: Any mass persisting beyond 2-3 weeks
- Adult patient: Especially those >40 years with cystic neck masses
- Concerning features: Any of the red flags mentioned above
- Inconclusive physical exam: When physical examination cannot definitively distinguish between lymph node and cyst
Diagnostic Approach
Ultrasound: First-line imaging for both lymph nodes and cysts
- Can distinguish solid from cystic components
- Can identify features suggestive of malignancy
Fine-needle aspiration (FNA):
- Should be used as first-line for histologic assessment 2
- May need to be repeated for cystic lesions, targeting solid components or cyst wall
Core needle biopsy:
- Provides larger tissue sample when FNA is inconclusive
- Higher diagnostic yield than FNA
Open biopsy:
- Reserved for when less invasive methods are inconclusive
- Excisional biopsy preferred for cystic masses to reduce risk of tumor spillage 2
Remember that physical examination alone may not be sufficient to distinguish between benign and malignant processes, particularly with cystic lesions. When in doubt, imaging and tissue diagnosis are essential for accurate diagnosis and appropriate management.