Cervical cytology

Author: Mikael Häggström
Cytology of the cervix:

Clinical information

It is not necessary to look through more than readily available reports from previous cervical cytologies.

Magnification

While being fairly new to cervical cytology, preferably start looking at a high magnification such as 20x objective (with 10x eye piece). For suspicious findings, you may magnify up to maximum. On the other hand, once the pattern feels repetitive you can try switching to a slightly lower magnification such as 10x.

Adequacy

Adequacy should always be stated, either as "Satisfactory" or "Unsatisfactory". For estimating the number of cells, determine the following:

• The area of your field of view at high power (see the Evaluation chapter)
• The total size of the relevant area on the microscope slide. A ThinPrep is about 360 mm².
• Look at 10 representative high power fields (HPFs) within that area, and calculate the average number of cells per high power field.

HPF example on a ThinPrep (about 360 mm²). If 10 fields gives a total of 40 cells, it will be 4 cells per HPF. The area of this field is 0.23 mm². Therefore, total cellularity is estimated to be:
4 cells * 360mm² / 0.23mm² = 6260 cells.

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  You may count 10 fields either across the slide, or 5 fields in each direction.

Total number of cells = Average number of cells per HPF *

Total size of area HPF area

Conventional smear cellularity should be at least 8,000 cells. Liquid-based cytology cellularity should be at least 5,000 cells. Also a conventional smear is inadequate if >75% of cells are obscured by blood, exudate or air-drying artefact.

Eventually you will be able to tell when most cases are adequate or inadequate without performing a detailed calculation.

Transformation zone presence

Squamous metaplasia also counts as endocervix. Typical features are annotated. Pap stain.

State whether the endocervical/transformation zone is present or absent. Count an endocervical component as present if there are 10 or more endocervical or squamous metaplastic cells.

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  Endocervical cells can be viewed from the side as nuclear polarity (margination towards the same side as others) in a “picket-fence” configuration.
• 
  Sheets of endocervical cells have a honeycomb pattern.

In patients with previous hysterectomy, simply report glandular or squamous metaplastic cells as such, rather than stating the presence of a transformation zone, since they are likely vaginal in origin in such patients.

Very common findings

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  For reporting, acute inflammation should be a background of ample dispersed neutrophils, and not only aggregates of neutrophils with cells or mucus.
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  Vaginal squamous cell with normal vaginal flora versus bacterial vaginosis on Pap stain. Normal vaginal flora (left) is predominantly rod-shaped Lactobacilli, whereas in bacterial vaginosis (right) there are clue cells, covered in bacteria. A significant amount of clue cells can be reported as "Shift in vaginal flora suggestive of bacterial vaginosis".
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  Candida, seen as pseudohyphae.

Main conditions to exclude or confirm

Squamous atypia, seen mainly as cells with increased nucleus/cytoplasm ratio, nuclear hyperchromasia and irregular nuclear outline.

If the slide has been previously marked by a cytotechnologist or other previewer, grade the marked cells first. Then, you only need to look for worse findings on the rest of the slide.

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  Atypical squamous cells of undetermined significance (ASCUS), with only few slightly atypical cells
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  Low-grade squamous intraepithelial lesion (LSIL), here compared to an unremarkable intermediate squamous cell.
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  High-grade squamous intraepithelial lesion (HSIL), showing even more prominent features, and decreased cytoplasm, causing a high nuclear/cytoplasmic ratio.
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  Cytopathology of squamous cell carcinoma, keratinizing variant, with typical features. Pap stain.
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  LSIL and changes consistent with human papillomavirus (HPV), which is the presence of koilocytes, which show perinuclear cavitation, binucleation, nuclear hyperchromasia, and nuclear enlargement.

Cytopathology of squamous cell carcinoma, nonkeratinizing variant, with typical features. Pap stain. Necrotic debris (dirty background) is a feature that generally makes a HSIL case "suspicious for invasive squamous cell carcinoma". In contrast to the more distinct keratinizing variant, these findings are overall less specific, and most can be seen in other cancers such as adenocarcinoma as well (which, however, tends to have fine chromatin)

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  Distinguish HPV-changes from glycogenated squamous cells. Glycogen confers a yellowish color to the cytoplasm. It can look like the perinuclear cavitation of koilocytes, but has more rounded edges.

Clinical implication

If you are uncertain of the degree of dysplasia, it can be useful to look up how much difference it will likely make for the management of the patient. You may make an Internet search for the management of abnormal cervical screening in your region (such as The ASCCP tool for management in the US). A change from close follow-up to colposcopy is not that big of a deal, but if one of the alternatives will lead to a diagnostic excision, make sure that the case is looked upon by commensurate expertise.

Other findings

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  Chlamydia trachomatis, with granular cytoplasm with multiple intracytoplasmic inclusions with central small coccoid bodies.

Report

Example in a normal case:

Cervical/endocervical ThinPrep: Negative for intraepithelial lesion or malignancy (NILM).

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