Fine Needle Sampling Flashcards
What is Cytology?
Study of cell number and type in a tissue mass or fluid accumulation to investigate the cause
Common Cytological Specimens
Fine needle samples
Capillary action sample (just use needle)
Aspirate (needle and syringe)
Touch imprints - press glass slide up against surface
Bodily fluids
Lavages
Fine Needle Capillary Sample
With no suction
No syringe attached to needle
Insert into lesion
Redirect needle within lesion
Can’t assume uniform consistency and need representative sample
Fine Needle Aspirate
Minimal suction
Needle attached to syringe to provide the suction
Used for cysts or failed FNCS
What does cytological examination allow?
Differentiation of inflammation from tissue growth
Hyperplasia/neoplasia
Differentiation of types of inflammation
Detect neoplasia
Malignant vs benign
Should indicate general type of neoplasm
□ E.g. sarcoma vs carcinoma
May identify the specific neoplasm
Differentiation of different fluids
Exudates, transudates etc.
Advantages of Fine Needle Sampling
Safe
Inexpensive
Cells can often be safely retrieved from lesions near vulnerable structures in conscious animals
○ Making anaesthesia & surgical biopsy unnecessary
Sampling demands little equipment or skill
○ Although takes practice
Results can be quickly available
Limitations of Cytology
False negatives
False positives
Doesn’t provide information on tissue architecture
Doesn’t provide information on invasion
Reasons for false negatives
Poor exfoliation of a neoplasm
Failure to sample tumour tissue
Extensive necrosis/inflammation present
Neoplasm may not be well-differentiated enough to allow an accurate diagnosis
Reasons for False positives
Dysplasia (which can mimic neoplasia) may occur in inflammatory diseases
Inflammatory Dysplasia
Proliferative changes and atypical morphology in some cells
E.g. mesothelial cells
Caused by inflammation/irritation
Morphology can revert to normal if the irritant is removed
Cytology VS Histopathology
Cytology
* Minimal patient prep and restraint
* Doesn’t always require sedation
* Dry, stain, dry in minutes
* Microscopic review <5mins
* “bricks” rather than buildings
* Architecture seldom preserved – cells come through a hypodermic needle
* Not always conclusive
Histopathology
* More patient prep, restraint anaesthesia as more invasive (Tru-cut, incisional, excisional)
* Takes longer and more complex process
○ Fix in formalin - overnight
○ Trim, process (dehydrate) embed in wax, slice, stain, coverslip - Minimum 1 day
* Architecture preserved
○ Even if obtained by biopsy needle
* More often conclusive
Lesion Types
Inflammation
Neoplastic
Cystic
Inflammation lesions
Neutrophilic
○ Non-degenerate vs Degenerate
○ Septic vs no organism seen
Eosinophilic
Granulomatous
Neoplastic lesions
Epithelial
Round
Mesenchymal
Benign vs malignant
Cystic lesions
Epidermal
○ Squames
Sialocoele
○ Saliva
Seroma
○ Serum
Haematoma
○ Blood
