Cytology

Cytology

What is
1. Cytology
  1. The scientifc study of the structure & function of cells
  2. Cyto Vs Histo
    1. Cyto
      1. Cells, Direct Smear Prep, Indirect prep, Same day Staining, Diag same day, preliminary by cyto tech
    2. Histo
      1. Tissue, Requires Dissection, Wax embedding, Cutting Sections, Clear-stain, Diagnosis by pathologist
2. CytoPathology
  1. Branch concerned with examination of cells in health & disease for screening, diagnostic & research purposes.
    1. Screening
      1. examination of samples from asymptomic individuals in order to detect pre-malignant or early malignant changes
      2. Via light microscope
Types of cytology specimens
1. Exfoliation
  1. Cell shed naturally, exfoliated from epithelial surface. Cells in urine, sputum, nipple discharge. Different from cells taken forcibly - they appear as small clusters without order, spherical & susceptible to degenerative changes
2. Abrasion
  1. Cells obtained using physical force. Eg. Brushings - bronchus, cervix, Scrapings - cervix, skin, nipple, Lavage - bronchus. Such cells are generally well preserved in large groups or cohesive aggregates.
3. Aspiration
  1. Fine Needle Aspiration (FNA) - sites that accessed via needle yielding cellular material for examination. Radiological imaging assists in localising small, deep, mobile legions. Cells removed via needle w/ or w/out suction from a fluid filled cavity or solid tissue.
    1. 19-25 gauge needle on syringe. Needle inserted into lesion, syringe plunger is partially withdrawn - creating a vacuum & aspirating lesion cells. Plunger is released to equalize pressure, needle is withdrawn and cells are fixed.
      1. Sites - Tumours eg. breast, prostate, thyroid. Pericardial - the double walled sac that contains the heart. Pleura - body cavity that surrounds the lungs. Peritoneal fluid - serous memb forms the lining of the abdominal cavity. CSF - clear bodily fluid in the subarachnoid space and the ventricular system around and inside the brain & spinal cord. Vitreous humour - clear gel that fills between lens & retina of eyeball.
Cytology prep techniques
1. Cell Concentration Techniques
  1. Centrifugation
    1. Suitable for large volume samples - serous effusions (pleural or peritoneal), Urine, Salinated lavage. Spin to concentrate sample, remove supernatant, make slides for precipitate.
  2. Cytocentrifugation
    1. Utilizes small aliquots of fluid. Spun directly onto microscope slides. Forms localised monolayer of cells. Suitable for low vol. Some material is lost on filter paper viscid or cellular specimens are unsuitable
  3. Memb filtration
    1. Uses positive pressure or vacuum filtration. Various types of filter paper with diff pore sizes may be employed - cellulose acetate, polycarbonate. Suitable for wide range of large vol specimens, or hypocellular fluid specimens. May yield greater cell capture than centrifugation,
  4. Cell block prep
    1. Cell are aggregated into a tissue-like state. Allows cell block to be cut using conventional histology techniques. Eg. plasma fibrin clot - utilising plasma & agar cell block with hot agar. Suitable for most cell suspensions. Allows special staining including immunocytochemistry.
2. Smearing Techniques
  1. Smear should be evenly spread, uniformly thin and flat - allows for rapid drying & permits optimal penetration of stain.
  2. Direct
    1. Involves spreading fresh material across slide using another slide, pick or spatula.
  3. Indirect
    1. Material suspended in fluid, eg. saline or transport medium. Cell concentration procedure may be performed to increase the yield. Clot formation may sequester much of the cellular material. If clot cannot be dispersed by mechanical means then process as a cell block & submit for conventional histo.
      1. Cell deposits from washings and urine may not adhere to glass slides. An adhesive may be employed - proteinaceous, ionic. These will enhance adherence & maximise the cellular material for examination.
  4. Other
    1. Touch Imprints - not v common
    2. Scrapings
    3. Squash prep - employed in preneurosurgical diag - in preference to conventional histo on frozen sections.
3. Specimen Fixation
  1. Wet Fixation
    1. Dehydrates the protoplasm & coagulates protein.
      1. Alcohol based - immersion or coating. Induces a degree of shrinkage
      2. Polyethylene glycol in alcohol - provides protective waxy coating, useful if specimens need to be posted, must be thoroughly removed prior to subsequent fixation.
      3. Or Glutaraldehyde, formalin, Carnoy's fluid (ethanol chloroform glacial acetic acid)
  2. Air drying
    1. Relies on evaporation. Must be rapid. Facilitate by forced air movement rather than passive. Tends to flatten cells - cell may appear larger than when wet fixed. Post-fixation in methanol prevents cross infection.
Cytology staining Techniques
1. May also be employed on cytopreparations.
2. Papanicolaou (Pap) stain, Romanowsky stains (May-grunwald-Giemsa & Diff Quick), haematoxylin & Eosin
  1. Pap
    1. For wet fixed. Commonly employed for gynaecological specimens. Differential staining pattern permits prolonged periods of microscopy with minimal eye-strain
  2. Romanowsky
    1. For air dried. May be automated or rapid manual. Most common on non-gynae. 2 types: May-Grunwald-Giemsa, & Diff Quick
  3. Haematoxylin & Eosin
    1. For air dried. Favoured by some who are familiar with this method for histo. Numerous other staining techniques may be employed. eg. Periodic-acid-schiff (mucosubstances & glycogen), Trichrome stains ( Ziehl-Neelson & Gram), All immunocytochemical stains (microorganisms or tumor)

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	Created by sam.wats over 10 years ago