Overview and Clinical Importance
Cytology and coagulation testing are fundamental diagnostic tools in veterinary medicine that provide rapid, cost-effective information for clinical decision-making. Cytology allows practitioners to differentiate inflammatory from neoplastic processes, guide treatment decisions, and stage tumors without invasive surgical biopsies. Coagulation testing is essential for diagnosing bleeding disorders, monitoring anticoagulant therapy, and assessing patients with suspected disseminated intravascular coagulation (DIC).
For the BCSE examination, this topic integrates knowledge from pathology, medicine, and diagnostics domains. Questions typically focus on proper sample collection techniques, interpretation of cytologic findings to differentiate inflammation from neoplasia, body fluid classification, and the diagnosis and monitoring of coagulation disorders including DIC.
High-YieldCytology and coagulation questions on the BCSE emphasize CLINICAL APPLICATION. Expect questions that provide clinical scenarios requiring you to select appropriate collection techniques, interpret findings, or diagnose conditions based on laboratory results.
| Feature |
FNA with Aspiration (FNAC) |
FNA without Aspiration (FNNAC) |
| Technique |
Needle attached to syringe; negative pressure applied during sampling |
Needle alone (no syringe); cells collected by capillary action and cutting motion |
| Equipment |
21-23G needle, 2-5 mL syringe |
21-25G needle only |
| Cellularity |
Generally higher cell yield |
May have lower cellularity |
| Blood contamination |
Higher risk of hemodilution |
Less blood contamination |
| Best for |
Lymph nodes, solid masses, firm tissues |
Highly vascular organs (liver, spleen, thyroid), fragile tissues |
| Cell preservation |
Good if technique is correct |
Often better preservation with less rupture |
| Technique |
Best Applications |
Key Considerations |
| Impression Smear |
Ulcerated lesions, cut surfaces of tissues, ear cytology |
Remove surface debris/blood first; blot gently; multiple impressions from different areas |
| Scraping |
Skin lesions, keratinized tissues |
Use scalpel blade held perpendicular; scrape until capillary bleeding |
| Swab Collection |
Ear canal, vaginal, nasal, fistulous tracts |
Roll (do not smear) swab across slide to preserve cells |
| Fluid Collection |
Body cavity effusions, joint fluid, CSF |
Collect into EDTA tube; make direct smears and concentrate by centrifugation |
| Lavage/Wash |
Tracheal wash, bronchoalveolar lavage, bladder wash |
Use sterile saline; rapid processing important for cell preservation |
| Type |
Predominant Cells |
Common Causes |
| Purulent/Suppurative |
Neutrophils greater than 85%; may be degenerate if septic; intracellular bacteria may be present |
Bacterial infection, foreign body, abscess, septic peritonitis |
| Pyogranulomatous |
Mixed population of neutrophils and macrophages; may see epithelioid macrophages |
Fungal infection, mycobacteria, foreign body reaction, FIP in cats |
| Granulomatous |
Macrophages predominate (greater than 70%); may form giant cells; few neutrophils |
Chronic fungal infection, mycobacteria, lipid-laden inflammation |
| Eosinophilic |
Eosinophils greater than 10-20%; often mixed with other inflammatory cells |
Parasites, allergic/hypersensitivity, eosinophilic granuloma complex, mast cell tumor |
| Lymphocytic/Plasmacytic |
Small lymphocytes and plasma cells predominate |
Chronic antigenic stimulation, immune-mediated disease, some viral infections |
| Category |
Feature |
Description |
| Nuclear Criteria |
Anisokaryosis |
Variation in nuclear size; significant if greater than 2:1 ratio between cells |
| Nuclear Criteria |
Increased N:C ratio |
Nucleus occupies greater proportion of cell than normal |
| Nuclear Criteria |
Multinucleation |
Multiple nuclei, especially if different sizes |
| Nuclear Criteria |
Prominent/multiple nucleoli |
Large, angular, or variably-sized nucleoli |
| Nuclear Criteria |
Abnormal mitotic figures |
Asymmetric, multipolar, or lagging chromosomes |
| Nuclear Criteria |
Coarse chromatin |
Irregular, clumped chromatin pattern |
| Nuclear Criteria |
Nuclear molding |
Nuclei conform to shape of adjacent nuclei |
| Cytoplasmic |
Anisocytosis |
Variation in cell size |
| Cytoplasmic |
Cytoplasmic basophilia |
Increased blue staining due to high RNA content |
| General |
High cellularity |
Cells exfoliate readily in sheets or clusters |
| General |
Cellular pleomorphism |
Variable cell morphology within population |
| Feature |
Reactive Hyperplasia |
Lymphoma |
| Cell population |
Heterogeneous; mixed small, medium, and large lymphocytes |
Monomorphic; greater than 50% intermediate to large cells in high-grade lymphoma |
| Small lymphocytes |
Predominate (greater than 50-70%) |
Minority (less than 50%) or absent |
| Plasma cells |
Often increased |
Usually absent or rare |
| Mitotic figures |
Rare to occasional |
Often frequent (greater than 3 per 5 high-power fields) |
| Criteria of malignancy |
Absent |
Variable; may see anisokaryosis, multiple nucleoli |
| Tingible body macrophages |
May be present |
Often increased (starry sky pattern) |
Part 1: Cytology
Collection Techniques
Proper sample collection is the foundation of diagnostic cytology. The goal is to obtain adequate cellularity with good cell preservation in a monolayer format suitable for microscopic evaluation. Multiple techniques exist, and selection depends on the tissue type, lesion characteristics, and clinical situation.