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Liquid based cytology

Sami Talibi, M.D.
Sadia Sayeed, M.D.

Last author update: 3 March 2022
Last staff update: 3 March 2022

Copyright: 2021-2024, PathologyOutlines.com, Inc.

PubMed Search: Liquid based cytology[TI] free full text[SB] "last 5 years"[DP]

Sami Talibi, M.D.
Sadia Sayeed, M.D.
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Table of Contents
Definition / general | Essential features | CPT coding | Sites | Laboratory | Case reports | Cytology description | Cytology images | Molecular / cytogenetics description | Sample pathology report | Additional references | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2
Cite this page: Talibi S, Sayeed S. Liquid based cytology. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cytopathologyliquidbased.html. Accessed December 3rd, 2024.
Definition / general
  • Liquid based preparation (LBP): samples from various sources are collected or rinsed in a preservative solution; the cell suspension is then evenly distributed as a monolayer on a glass slide for examination
    • The 2 most popular methods used today are ThinPrep (Hologic, Marlborough, Massachusetts) and SurePath (Becton Dickinson and Company, Franklin Lakes, New Jersey)
Essential features
  • LBP allows for easier processing, potential for automation (for cervical pap tests), fewer slides required per case and less screening time compared with conventional / direct smears
  • Improvements in identification of morphologic features with less air drying artifact, improved nuclear and cytoplasmic details, reduction in background blood and inflammation and increased cellularity
  • Familiarity with known pitfalls is needed: i.e., cell clusters / papillae are broken up, smaller cell size, more prominent nucleoli in benign conditions, lack of background mucin, necrosis or change in quality of background elements
CPT coding
  • Gynecological:
    • Diagnostic Pap test:
      • Manual screening:
      • Automated screening:
  • Nongynecological:
    • 88112 - enriched / concentrated preparation (e.g., liquid based slide preparation: ThinPrep, SurePath)
  • FNA:
    • No specific separate charge
Sites
  • Gynecological: cervix, vagina (Pap test)
  • Body cavity fluids (pleural, peritoneal, pericardial)
  • Cerebrospinal fluid (CSF)
  • Gastrointestinal (GI): anal (Pap test), pancreas, bile duct, liver
  • Genitourinary (GU): urethra, bladder, ileal conduit, renal pelvis, ureter
  • Respiratory: bronchus, lung
  • Hematologic: lymph nodes
  • Head and neck: thyroid, salivary gland
  • Breast
Laboratory
  • Specimen collection:
    • Collection medium: methanol based PreservCyt (for ThinPrep Hologic, Marlborough, Massachusetts) and CytoRich Red preservative fluid (SurePath Becton Dickinson and Company, Franklin Lakes, New Jersey)
    • Cervical or vaginal sample:
      • ThinPrep: collection using Rovers Cervex-Brush Combi device (a green broom-like device with an integrated endocervical sampler), endocervical brush or spatula
        • Following collection, the device is rinsed in the PreservCyt vial, then vigorously swirled before discarding
      • SurePath: collection using broom-like devices (Rovers Cervex-Brush Device and Rovers Cervex-Brush Combi Device), endocervical brush or spatula
        • Following collection, the device is placed in the vial; the device head is pulled or snapped off and remains in the vial
    • Anal sample:
      • ThinPrep: using moistened Dacron swab or cytobrush to collect sample, rotate in collection medium, then vigorously swirl device before discarding
      • SurePath: using moistened swab collect sample, place in SurePath vial; the device head remains in the vial
    • Brushing (bronchial, bile duct): rinse device into collection medium
    • Fine needle aspiration (FNA) sample: collect needle rinse / aspiration material directly into collection medium
  • Specimen processing:
    • SurePath:
      • Sample is vortexed then passed through a small opening using a syringe device (causing disaggregation)
      • Sample is poured into a centrifuge tube with a density gradient reagent
      • Specimen is centrifuged and the pellet is resuspended; this step is repeated 5 times
      • Tubes are then transferred to the PrepStain instrument
        • Robotic arm transfers the fluid into a cylinder, the cells settle into a cationic polyelectrolyte coated slide, a 13 mm diameter deposit is made
        • Staining is performed in the same instrument using the robotic arm
    • ThinPrep:
      • Vial is placed on a stage and a plastic cylinder with a 20 mm diameter; a polycarbonate filter is bonded to the surface and is inserted on top of the vial
      • Rotor spins the cylinder, dispersing the cells, then a vacuum is applied to the cylinder to trap the cells onto the filter
      • Instrument monitors the cell density on the filter; once a threshold is reached, the cylinder with the attached filter is inverted 180 degrees
      • Filter is pressed on to a glass slide, creating a 20 mm diameter deposit
      • Slide is immediately dropped into an alcohol bath
      • Staining is performed in a separate device
  • Advantages (compared with conventional smear technique):
    • General (Diagn Cytopathol 2013;41:257):
      • Standardization of processing
      • Minimal air drying artifact from immediate fixation
      • Compatible with automated screening devices
      • Allows batch processing
      • Residual sample can be used for additional testing (human papillomavirus [HPV], Neisseria gonorrhoeae [GC], chlamydia, cell block, florescent in situ hybridization [FISH], molecular testing)
      • Uniform distribution of cells in a monolayer with less overlap
      • Lower rate of unsatisfactory samples
      • Minimal cell loss
      • Less screening time
      • Reduction in inflammation or blood in background
      • Useful when onsite evaluation is unavailable
    • SurePath:
      • Staining step included in processing
      • Better reduction in background blood
    • ThinPrep:
      • T5000 processor allows for 20 samples to be processed at once
      • Fully automated, hands free process
      • Less operator training required
  • Disadvantages:
    • General:
      • Does not allow for real time adequacy assessment
      • Some ancillary tests cannot be performed: microbial culture, flow cytometry
    • SurePath:
      • More manual steps (centrifugation steps)
      • More operator training required
      • Cells have a more 3 dimensional distribution
    • ThinPrep:
      • Staining performed separately
      • More collection training required to prevent unsatisfactory sample collection (cervical, vaginal and anal samples)
      • Excess blood may be present
      • Loss of background material needed for diagnosis
Case reports
Cytology description
Cytology images

Contributed by Sadia Sayeed, M.D.
LSIL ThinPrep

LSIL ThinPrep

HGSIL ThinPrep

HGSIL ThinPrep

HGSIL SurePath

HGSIL SurePath

Benign endocervical cells ThinPrep

Benign endocervical cells ThinPrep

Adenocarcinoma ThinPrep   Adenocarcinoma ThinPrep

Adenocarcinoma ThinPrep


Reactive mesothelial cells ThinPrep

Reactive mesothelial cells ThinPrep

Benign, BAL

Benign, BAL

HGUC, urine

HGUC, urine

Suspicious thyroid aspirate

Suspicious thyroid aspirate

Benign thyroid aspirate

Benign thyroid aspirate

Molecular / cytogenetics description
  • Urine cytology:
  • Biliary duct brushing:
    • Combination of FISH probes 1q21, 7p12, 8q24 and 9p21 useful for the identification of biliary tract malignancy, with a significantly higher level of sensitivity (64.7%) than UroVysion probes (Gastroenterology 2015;149:1813)
      • Samples collected in PreservCyt or CytoLyt
  • Thyroid FNA:
    • See Molecular testing in FNA
    • Using 6 groups of 10+ follicular cells as a cutoff, nearly 97% of thyroid FNA samples collected in ThinPrep vial contained enough DNA for BRAF mutational assay (200 ng of DNA used as minimum criteria) (Cancer Cytopathol 2014;122:114)
    • 18 gene next generation sequencing panel successfully performed from residual ThinPrep sample (J Cancer 2020;11:7276)
      • Lower negative predictive value but a higher positive predictive value, compared to ThyroSeq v2 testing (J Cancer 2020;11:7276)
    • Cellularity and storage time may affect the quantity and quality of nucleic acid extracted from thyroid FNA specimens collected in CytoLyt (Cancer Cytopathol 2020;128:656)
Sample pathology report
  • Pleural fluid, thoracentesis:
    • Specimen adequacy:
      • Satisfactory for evaluation
    • Microscopic interpretation:
      • Malignant cells present
      • Metastatic adenocarcinoma
      • Cell block shows similar features
Board review style question #1


Regarding cervical cytology, which of the following is a known difference observed in liquid based preparation when compared with conventional smears?

  1. Larger cell size
  2. Larger cellular aggregates
  3. Larger nuclear size
  4. Nucleoli are less visible
  5. Reduction in background blood and inflammation
Board review style answer #1
E. Reduction in background blood and inflammation (Demay: The Art & Science of Cytopathology, 2nd Edition, 2011)

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Reference: Liquid based cytology
Board review style question #2
A pleural effusion sample has been entirely placed in a ThinPrep vial and processed. A single ThinPrep slide and cell block has been created. The clinical information received with the specimen is "rule out lymphoma". Which known limitation of liquid based preparation applies in this scenario?

  1. FISH studies cannot be performed
  2. Flow cytometry cannot be performed
  3. Immunohistochemistry cannot be performed
  4. Microbial culture cannot be performed
  5. Molecular testing cannot be performed
Board review style answer #2
B. Flow cytometry cannot be performed. Since the specimen was entirely placed in the methanol based ThinPrep vial, flow cytometry and microbial culture tests cannot be performed. Flow cytometry may be required for diagnosis when the clinical suspicion includes lymphoma. Immunohistochemistry, molecular testing and FISH studies can all be potentially performed on the cell block. In some instances, molecular and FISH testing can be performed on residual sample collected in ThinPrep vials.

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Reference: Liquid based cytology
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