8
UNIT 1
Basic Principles of Cell Structure and Function
Metaplasia.
H&E,
3
199
Metaplasia
is the reversible change of one mature cell type to another as a
result of an environmental stimulus. Examples of metaplasia include squamous
metaplasia of the endocervical glandular epithelium of the cervix, squamous
metaplasia of ciliated respiratory epithelium in smokers, and intestinal meta-
plasia of gastric mucosa as a result of chronic gastritis.
Image:
A section of stomach shows chronic gastritis with intestinal metaplasia.
Note the presence of goblet cells (
arrow
) not normally present in the gastric
mucosa.
Monomorphism.
H&E,
3
155
Monomorphism
is a term describing cell populations that show little difference
in size and shape of the cell itself, the nucleus, or both. Benign neoplasms and
well-differentiated malignant neoplasms may be monomorphic.
Image:
This image shows a monomorphic population of cells in a duodenal gas-
trinoma. The cells are relatively uniform in size and shape, as are the nuclei.
Multinucleation.
H&E,
3
155
Most normal cells contain a single nucleus,
with the exception of the osteoclast, which is
multinucleated
. Multinucleated cells can be
seen in a variety of conditions including reac-
tive bone conditions, malignant bone and soft
tissue tumors, granulomatous infl ammation,
and foreign body giant cell reactions.
Images:
The F
rst image (
left
) shows a giant
cell (
arrow
) in a granuloma of sarcoidosis.
The second image (
right
) shows an extensive
foreign body giant cell reaction (
dashed line
)
to suture material (
arrow
).
Pleomorphism.
H&E,
3
199
Pleomorphism
is a term describing cell populations that show differences in
the size and shape of the cell itself, the nucleus, or both. It is typically used to
describe neoplasms. In general, poorly differentiated malignant neoplasms may
have a pleomorphic appearance.
Image:
This image shows extreme cellular and nuclear pleomorphism in this
case of malignant F brous histiocytoma, pleomorphic type. Compare this image
to that of the monomorphic gastrinoma above.
Pyknosis.
H&E,
3
747
Pyknosis
is a morphologic change in the nucleus of an irreversibly damaged
cell characterized by condensation and increased basophilia.
Image:
This image shows pyknosis (
arrow
) in a dying cell in a malignant
neoplasm.
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