General Cytology
cytotechnologists, who screen all samples, and cytopathogists
who are responsible for the final interpretation of all abnormal
Sample Adequacy Assessment
Over the years there has been considerable debate about what
constitutes an adequate sample. In the 2001 Bethesda con-
ference this issue was addressed and specific guidelines for
assessing sample adequacy emerged. Applying the minimum
squamous cellularity criteria a cellularity of 10,000 to 12,000
squamous cells is considered adequate for conventional Paps.
There is no need to count squamous cells but rather estimate
the cellularity based on density cell patterns in reference
images. In samples with cytolysis, atrophy, and cell clustering,
when cell adequacy is borderline, professional judgment and
hierarchical review is recommended. The presence or absence
of endocervical cells/transformation zone component does
not affect sample adequacy but should be mentioned as a
quality factor. Specimens with more than 75% of squamous
cells obscured should be termed unsatisfactory assuming that
no abnormal cells are present. For liquid-based preparations
5,000 squamous cells is considered adequate cellularity and
estimates are reached by counting the number of cells in ten
high-power fields across the main diameter of the preparation.
Using a 40x objective and FN20 eyepiece the number of cells
in each field should be 3 for the ThinPrep and 7 for the Sure-
Path for adequate cellularity.6
Unsatisfactory sample rates are variable. Centrifugation LBP
have a lower rate of unsatisfactory samples than filtration-based
preparations because in the latter red blood cells or inflam-
matory cells may plug the filter pores. Reprocessing is recom-
mended to lower the unsatisfactory rate.7,8
A meta-analysis of prospective studies comparing cytologic
diagnosis and sample adequacy showed LBP improved sam-
ple adequacy and equal or superior results in diagnosing pre-
malignant cervical lesions when compared with conventional
Papanicolaou test.9 In a comparison study of automated versus
manual LBP few differences were found in the sample adequacy
and cellular presentation: less uniform distribution of cells
and more artifacts were noted in the manual methods such as
DNA Citoliq and AutoCyte Prep compared with the ThinPrep
method; sample adequacy and overall quality of all LBP were
surprisingly good.3
Detailed criteria for the interpretation of gynecologic samples
are described in Chapters 6-11 of this book. The following high-
lights some observations in LBP.6,10-14
For LBP fixed in ethanol-based fixative the interpretation is
closer to conventional smears. When LBP are concentrated in
smaller areas, with three-dimensional cell clusters above the
plane of squamous cells, focusing may be required more often.
There are many similarities in the evaluation of LBP and
conventional smears but there are differences:
• Cell size;
• Pattern; and
• Background.
Because samples are collected in a liquid-based fixative solu-
tion, the presentation of the cellular material appears differ-
ent, concentrated and evenly distributed (Fig. 5.1). Cells are
smaller, dispersed, and single, although cell clusters are also
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Fig. 5.1 Normal squamous and endocervical cells
appear evenly
distributed. Surepath (papanicolaou x Lp).
present. Cells in solution tend to round up and wet fixation
enhances cytoplasm and nuclear morphology. Hyperchromasia
as observed in abnormal cells on conventional smears is not
always present in liquid-based preparations, especially in meth-
anol-based fixatives, and lack of hyperchromasia may render
the interpretation of high-grade squamous intraepithelial lesion
more difficult. Variations in nuclear size and shape and espe-
cially appreciation of nuclear contours play an important role
in the evaluation on LBP.
The background is generally clean and debris more clumped.
Blood, mucus, and inflammation are rarely obscuring, and
inflammatory cells tend to cling to epithelial cells. Tumor dia-
thesis has a "ratty" appearance but this type of background can
also be observed with cytolytic or inflammatory patterns.
Some cytologic entities have key features in LBP:
Key features of atrophy
• Fewer bare nuclei;
• Flat sheets of parabasal cells; and
• Preserved nuclear polarity (Fig. 5.2) .
Key features of trichomonads
• Smaller;
• Difficult to visualize; and
• More visible nuclei, eosinophilic granules, or flagella.
Key features of lymphocytic cervicitis
• Lymphoid cells in clusters; and
• Confused with endometrial cells (Fig. 5.3) .
Key features of repair
• Cohesive cell groups;
• More rounded cytoplasmic borders;
• Less streaming; and
• Prominent nucleoli.
Key features of metaplastic cells
• Often single, smaller, and rounder;
• Confused with HSIL; and
• Paler chromatin pattern.
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