What lab test should I order for the sample obtained from a cyst removal?

Surgical Pathology Examination for Cyst Specimens

For a cyst removed from a patient, the appropriate laboratory test to order is a surgical pathology examination. This is the standard practice for all excised tissue specimens to determine the nature of the cyst and rule out any malignancy 1.

Classification of Cysts and Pathology Requirements

Different types of cysts require pathological examination for proper classification and management:

Simple vs. Complex Cysts

• Simple cysts: Typically benign with minimal risk of malignancy
• Complicated cysts: Have low-level echoes or debris with <2% risk of malignancy
• Complex cysts: Contain solid components with 14-23% risk of malignancy 1

Pathology Examination Process

1. Gross examination: Document size, wall thickness, contents (clear fluid, bloody, purulent), uni/multilocularity, and presence of solid areas 2
2. Histological examination: Assess for:
   • Epithelial lining type
   • Presence of dysplasia (using two-tiered grading system: low vs high-grade) 2
   • Invasion into surrounding tissues
   • Special features specific to cyst type

Specific Requirements by Cyst Location

Pancreatic Cysts

For pancreatic cysts, pathology examination should include:

• Assessment of histological subtype (gastric, intestinal, pancreatobiliary)
• Documentation of dysplasia grade using a two-tiered system (low vs. high-grade)
• Evaluation for invasive components 2

Bladder Cysts

For bladder lesions, pathology should include:

• Depth of invasion assessment
• Margin status
• Presence of carcinoma in situ
• Lymphovascular invasion 2

Breast Cysts

For breast cysts, pathology examination should:

• Classify according to histological features
• Evaluate for atypical cells or malignancy
• Document if fluid was bloody (requiring cytologic examination) 1

Clinical Considerations

When to Send for Pathology

While some studies suggest that certain obviously benign cysts (like epidermoid cysts) might not always require histological examination 3, the standard of care remains to submit all excised cyst specimens for pathological examination to:

1. Confirm the clinical diagnosis
2. Rule out unexpected malignancy
3. Provide documentation for medical-legal purposes
4. Guide further management if needed

Special Situations

• If cyst fluid is bloody, cytological examination is mandatory 1
• For complex cysts with solid components, thorough histological examination is essential due to higher malignancy risk 1

Documentation on Requisition

When submitting the specimen, include:

• Patient demographics
• Cyst location
• Clinical impression/suspected diagnosis
• Relevant clinical history
• Any prior treatments to the area

Conclusion

Regardless of the presumed benign nature of a cyst, proper surgical pathology examination remains the standard of care for all excised tissue specimens. This ensures accurate diagnosis and appropriate follow-up care while minimizing the risk of missing an unexpected malignancy.