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Fine needle aspirate
Synonym(s): FNA
Overview
- Microscopic study of cells obtained from skin, lymph nodes, body fluids/exudates or internal organs.
- Cells are smeared onto a slide and stained, then viewed by light microscopy.
- Rapid results.
- Requires minimal equipment.
- However, cells in exudates may be difficult to separate/concentrate and stain usefully.
- Direct evaluation of neoplastic/inflammatory changes provided representative sample obtained.
- Requires skilled cytopathologists as some apparently neoplastic changes can be "normal".
Uses
Alone
- Superficial masses, hollow or fluid-filled structures.
In combination
- Sampling during surgical excision then follow up with histopathology.
- Sampling in association with ultrasonography.
Sampling
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Tests
Methodologies
- Modified Wright's stain or Giemsa stain: best for inflammatory lesions.
- Romanowsky-type quick stain: can adjust color as blue and red components are separate. Acceptable nuclear detail.
- Light microscopy: scan at 4x and 10x; use 40x and 100x for fine detail.
Validity
Sensitivity
- Less sensitive than histopathology because architectural detail is lacking and more difficult to obtain representative sample.
- More difficult to assess cell types.
- Requires cytopathologist.
Specificity
- Low compared to histopathology as may miss diagnostic cells.
- Good for discrete cell tumors, eg lymphoma, squamous cell carcinoma.
Technique intrinsic limitations
- Information about tissue architecture cannot be obtained.
- Often requires confirmation by histopathology.
Technician extrinsic limitations
- May be difficult to obtain representative sample.
- Skill required.
- Fairly low repeatability.
Result Data
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