Diagnostic Cytology
Fig. 8.32 Mature squamous metaplasia.
Singly lying, relatively
mature round-to-oval cells with relatively large nuclei. Cytoplasm showing
dense outer zone, "ectoplasm,” and lighter inner zone "endoplasm"
(Papanicolaou x OI).
• Cytoplasm displays a densely staining outer zone
(ectoplasm) and a central clear perinuclear zone
(endoplasm)—cyanophilic staining; and
• Nuclei are relatively small, centrally located, and uniform
in size and shape, and show finely granular, evenly dis-
tributed chromatin with occasional micronucleoli.
Cells from a slightly to moderately atypical squamous meta-
plasia change may pose major problems to the inexperienced
cytologists (Figs 8.33 to 8.35). Within this group of diagnosti-
cally difficult lesions is a subset associated with abnormal cyto-
logic smears. These lesions are colposcopically abnormal and
have the histologic and cytologic features of atypical immature
squamous metaplasia.20
The cytoplasm gives information related to the maturity and
specific tasks of the cell, whereas the nucleus reflects not only
maturity but also the degree of dedifferentiation of a cell (malig-
nant potential). Nuclei in atypical squamous metaplasia appear
to be large but only relative to the size of the cytoplasm. Abso-
lutely, the nuclei in atypical squamous metaplasia are much
smaller than nuclei in dysplastic changes. In squamous meta-
plasia, hyperchromasia is generally absent. Hyperchromasia
in nuclei of dysplastic cells reflects an abnormality in DNA
Fig. 8.33
Slightly atypical relatively
mature squamous metaplastic
Cells resembling ectocervical squamous cells with slightly irregular
somewhat enlarged nuclei. (Papanicolaou x OI).
synthesis, for example, an abnormal number of chromosomes
in that particular nucleus.
Mature squamous metaplasia is also referred to as:
• Epidermization (Fig. 8.36);
• Complete squamous metaplasia; and
• Squamous prosoplasia, stage V (Fluhmann).11
The word
means not normal, or not typical for a nor-
mal cell of this particular tissue. The term atypia is a minimally
defined descriptor in diagnostic cytopathology. It should not be
used as a noun but only as a descriptor of an observation with
additional specification of the severity of the atypia. When the
word atypia is used in a descriptive diagnosis, the degree of aber-
ration from the normal should be further specified, as should
what specific type of cells the observer has referred to. The use of
the word atypia without further specification should be avoided,
because it then can be used too often as a substitute for a careful
description and definition. The word atypia is commonly used
as a descriptive diagnosis when indicating minimal-to-slight
aberrations from normal. Features most frequently causing such
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