Clinical Cytology

1. Clinical Cytology

2. Clinical Cytology: Definition Cytology is the study of cell number and type in a tissue mass or fluid accumulation, to investigate its cause (usually inflammatory or neoplastic). Cells can often be safely retrieved from lesions near susceptible structures in conscious animals, making anaesthesia & surgical biopsy unnecessary.

3. Clinical Information Provided By Cytology • Differentiates fluids • Transudates, exudates, etc • Differentiates types of inflammation • Recognition of predominant cells in a lesion permits the type of inflammation • Should detect presence of neoplasia • Should indicate type of neoplasm • carcinomas, sarcomas or round cell tumours • May identify the neoplasm

4. Advantages • Quick • Inexpensive • Low risk to patient • Sampling demands little equipment or skill • Influence diagnostic pathway • Identify disease process (i.e. Neoplasia vs inflammation) • Anaesthesia or surgical biopsy are unnecessary

5. Technical Limitations • Inadequate specimen collection or handling • Inexperienced observer • Sample is not representative of the lesion • Sample is heavily contaminated with blood or other artifacts • Smear is not thin enough or is not air-dried quickly • Smear is badly stained

6. Touch imprints Often low cell yield Risk of contamination Scraping High cell yield Difficult to collect Only superficial samples Swabbing Useful for fistulous tracts, vaginal collection Fine needle aspirate Preferred method for masses Fluids & Lavages E.g. bronchial lavage Common Cytological Specimens

7. Cytological specimens: touch imprints • Biopsy & necropsy tissue can be examined to provide a rapid preliminary diagnosis. • Histopathological processing of the tissue may take several days to a week. • A small piece of tissue is grasped with a forceps, excess blood removed by touching it to tissue or a surgical swab, and cells from it are “dabbed” or imprinted on several cleaned glass slides. These are air-dried quickly and often stained with a simple blood stain, for immediate microscopic examination.

8. Fine Needle Aspirates (FNAs) • In an FNA, cells are aspirated from a superficial or deep mass or body organ; a thin smear is made, stained, and examined under a microscope. • The smears are dried rapidly by waving them in the air, or holding them in front of a fan or hair-dryer. Air-drying prevents artifactual shrinkage/distortion of cells. • A description of the mass, including size, location, texture and growth rate should always be provided with smears.

9. Cytological Specimens: Fluids Fluids may be obtained from peritoneal, pleural, pericardial, cerebrospinal and joint spaces, & fluid-filled lesions; the cell number and type helps to classify the fluids and provide clues to their origin. Peritoneal fluid is aspirated from a horse CSF drips from a dog

10. Cytological Specimens: Lavages Using sterile saline, cells can be washed from nasal, bronchoalveolar (BA) and urinary bladder mucosae, and retrieved by immediate aspiration of the lavage fluid Transtracheal lavage Broncho-alveolar lavage Broncho-alveolar lavage

11. Cytological Specimens: Lavages • Transtracheal lavage; a catheter is passed through a wide-gauge needle in a conscious dog, and fluid is flushed into the airway and quickly aspirated. Smears are made from a centrifuged sediment. • Bronchoalveolar lavage; fluid is lavaged through a catheter which has been passed through an endo-tracheal tube in an anaesthetised cat. • Broncho-alveolar lavage; using a bronchoscope; here, the fluid is lavaged through a bronchoscope in a conscious horse. In addition, bronchoscopy may permit a view of the lesion, and direct removal of cells from it using a tiny brush.

12. Stains • Usually a Romanowsky blood stain is used, e.g. Diff-Quik, Leishman, as these are simple to apply, quick, and give familiar coloration of cells. • Special stains may be used, e.g. Methylene Blue (general) or Toluidine Blue (for mast cell granules) or Periodic acid Schiff (PAS – for mucin). • If micro-organisms are present, or suspected to be present, stains such as Gram’s, Modified Ziehl Nielsen, PAS or Fontana’s may be used

13. Handling Cytology Specimens • FNA and imprint smears may be air-dried quickly, stained, and examined directly. • If fluid is available, the following points are assessed: 1. Appearance 2. Total protein content 3. Nucleated cell count 4. Cell type/content of fluid sediment

14. Handling Cytology Specimens • If aspirated fluid is turbid, direct smears are made. • If the fluid is clear, it is centrifuged and smears of the sediment are made. • The smears are quickly air-dried, stained and examined microscopically, and all contents are described • Other tests may be carried out, depending on history, signs, and cytological findings, e.g.: • -Bacteriology • -Viscosity (joint fluid) • -Enzymes, glucose content (cerebrospinal fluid)

15. Cerebrospinal Fluid (CSF) • CSF analysis is indicated in the evaluation of animals with suspected neurological disease, where alteration in the permeability of the blood-brain barrier may change CSF composition. • However, CSF analysis rarely provides a definitive diagnosis and there are some contra-indications.

16. Synovial fluid • Synovial fluid is collected with sterile precautions into EDTA & plain tubes. • In healthy animals it has a low protein content and nucleated cell count. • Two main functions: •Lubrication of the synovial lining of the joint • Providing nutrition to the chondrocytes in cartilage • Viscosity due to hyaluronic acid which is secreted locally. Analysis can be valuable in diagnosis when there is joint swelling, lameness or pyrexia of unknown cause.

17. Nasal lavage • Nasal lavage is used in the investigation of chronic nasal cavity disease - usually manifested by a chronic discharge • Sterile saline is flushed into the nose & aspirated (often under anesthesia), & fluid is centrifuged, smeared & stained for microscopic examination • NLmay contain material from the whole length of the nasal cavity • The discharge is more likely to be purulent if due to an infection or foreign body, and haemorrhagic if due to neoplasia, but many exceptions occur

18. Trans-tracheal (TTL) & broncho-alveolar lavage (BAL) • Performed in animals with clinical signs of respiratory disease of unknown aetiology. • Sterile saline is instilled into the tracheal or bronchoalveolar spaces, then aspirated and the cell content of the aspirated material is examined. • Can provide useful information in the diagnosis of tracheal, bronchial & pulmonary diseases.