Diagnostic Cytology
on the proximal to distal location within the canal, and the age
and hormonal status of the individual. Near to the area of the
squamocolumnar junction, the endocervical mucosa shows the
classically described pattern of tall columnar cells, with basally
placed nuclei, and cytoplasm which contains clear or pale
mucin contents (Fig. 9.1). This translates into cytologic prepa-
rations having similar features of tall columnar cells arranged
in a "picket-fence" appearance when viewed from the side
(Fig. 9.2), and the "honeycombed" appearance when viewed
on-end (Fig. 9.3). However, along its entire length, the histology
of the endocervical canal will gradually change into the clas-
sic histology of the lower uterine segment. Therefore, along this
gradient, the epithelium will change into a pattern more closely
resembling endometrium. Cell and nuclear sizes gradually
become smaller, the nuclei become more pseudostratified, and
the cytoplasmic content becomes darker as mucin production
fades. In addition, endocervical glands increase in number in the
midportions of the canal and thus sampling from this area will
Fig. 9.1 Typical endocervical canal epithelium. This simple epithelium
shows uniform nuclei located in the basal portion of the cells and mucus-
filled granular apical cytoplasm. This appearance is most characteristic of the
endocervical epithelium directly adjacent to the transformation zone (H&E x HP).
produce more endocervical cellularity and greater numbers of
endocervical groupings.10 A histologic example of endocervical/
lower uterine segment epithelium shows an example of the strik-
ing nuclear pseudostratification that may be present in this area
(Fig. 9.4), with its concurrent cytologic appearance (Figs 9.5,
9.6). In women in the later childbearing age group and older
(beginning in the mid- to late 30s), the endocervical canal can
show yet further changes from these classic patterns, with increas-
ing involvement by tubal metaplasia, as is also noted in this time
period commonly involving the endometrium. Tubal metapla-
sia is the changing of the normal endocervical appearance to
that mimicking the normal epithelium of the uterine tube. This
pattern consists of three commingled cell types, ciliated colum-
nar cells, goblet type mucin-producing cells, and slender interca-
lated cells. On cytologic examination, all three cell types can be
seen. Tubal metaplasia may present as hyperchromatic crowded
groups of cells (Fig. 9.7), often with pseudostratification (Fig.
9.8), and this pattern can lead to concerns about atypia and
even neoplastic processes.10 These features and their importance
in differential diagnosis with neoplastic entities will be further
covered in the section on "atypical glandular cells."
Another appearance of benign endocervical cells that must
be considered is that of spontaneously exfoliated endocervical
cells. These are individual cells that detach from the epithelial
surface and travel in the mucus of the endocervical canal before
being "picked up" by the sampling device. The "fluid" media
of the mucus causes the columnar cells to round up, giving
them a configuration akin to squamous metaplastic cells. Close
attention to cellular features such as frothy granular cytoplasm,
perinuclear vacuoles, and fine granularity of nuclear chromatin
with distinctive small nucleoli will help in the distinction from
cells of squamous metaplasia, or more importantly, from cells
of squamous metaplastic "atypia" (Fig. 9.9).
Human Papillomavirus (HPV), Other Cofactors,
and Their Role in Endocervical Carcinogenesis
Squamous and glandular neoplastic lesions of the cervix are
thought to be derived from a common progenitor cell, that being
the undifferentiated reserve cells that may normally mature along
Fig. 9.2 Typical "picket-fence" appearance in a cytologic specimen of directly sampled endocervical cells of the type noted in Fig. 9.1. When viewed from
the side, an identical appearance of basal nuclei and mucous apical cytoplasm is present (liquid-based preparation, Papanicolaou x (A) MP, (B) HP).
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