DYSPLASIA
Q. Write short essay/note on dysplasia.
The cells that show cytological features of malignancy and the term
dysplasia is used for these changes. It literally means disordered growth and
thus consists of disordered cellular growth and maturation. Dysplasia mostly
occurs in epithelial tissues. Normally, the cells of an epithelium show
uniform size, shape and nuclei and these cells are arranged in a regular
fashion, e.g., a squamous epithelium consists of plump tall basal cells that
progress to flat superficial cells.
Features of dysplasia: Dysplasia represents the morphologic expression of
a disturbance in growth regulation. However, unlike cancer cells, dysplastic
cells are not entirely autonomous, and with intervention, the cells can revert
to normal. In dysplasia, the normal pattern is disturbed and it shows
following changes:
v Cellular and nuclear pleomorphism characterized by loss in the
uniformity of the individual cells.
v Large hyperchromatic nuclei.
v High/increased nuclear-to-cytoplasmic ratio.
v Loss of polarity (architectural orientation), i.e., disorderly arrangement
of cells from basal layer to the surface layer, e.g., in dysplastic squamous
epithelium the normal progressive maturation may fail in part or entirely,
leading to replacement of the epithelium by basal-appearing cells with
hyperchromatic nuclei.
v Increased mitotic activity: Mitotic figures are normally confined to the
basal layer. In dysplasia, mitotic figures are more than in the normal
tissue and may be seen at all levels (instead of only basal cells), including
surface cells.
Sites of Dysplasia
v Squamous epithelium: Most common sites of dysplastic changes are
seen in the squamous epithelial lining of the uterine cervix (refer Figs.
22.2 and 22.3 and pages 740-1), respiratory tract and skin. Dysplasia
most common in hyperplastic squamous epithelium and in areas of
squamous metaplasia, such as in the bronchus or the cervix.
v Other epithelium: Dysplasia can occur in epithelium other than
squamous epithelium.
n Columnar mucosa: Dysplasia can occur in the columnar mucosal
cells of the colon in ulcerative colitis
n Ductal lining cells in breast
n Metaplastic epithelium of Barrett esophagus
n Prostate glands: Prostatic intraepithelial neoplasia
n Urothelium of the bladder
Asymptomatic: In this stage, they are usually asymptomatic.
Classification, Fate, and Significance
v Dysplasia can be classified as (1) mild, (2) moderate, and (3) severe
dysplasia depending on the thickness of epithelium involved by the
dysplastic cells.
n Mild-to-moderate dysplastic changes, which do not involve the
entire thickness of epithelium may be reversible, if the cause is
removed. The dysplasia may be a precursor to malignant
transformation, but dysplasia need not progress to cancer.
n Like metaplasia, dysplasia may develop as a response to chronic
irritation or prolonged/persistent inflammation. It may regress or
disappear after removal of the inciting stimulus, e.g., dysplasia in
bronchial epithelium may regress after cessation of smoking or
dysplasia in cervix due to human papilloma virus (HPV) may regress
following disappearance of HPV from the cervix.
n Dysplastic changes may be seen adjacent to foci of invasive
carcinoma. In some situations, such as in long-term cigarette smokers
and individuals with Barrett esophagus, severe epithelial dysplasia
may antedate the appearance of cancer.
v Carcinoma in situ: When dysplastic changes are marked and involve the
entire or full thickness of the epithelium, it is a preinvasive neoplasm and
is termed as carcinoma in situ (refer below). But the lesion does not
penetrate the basement membrane of the lining epithelium.
v Once the dysplastic/tumor cells breach the basement membrane, the
tumor is said to be invasive and carcinoma in situ may take years to
become invasive. Most in situ tumor, with time penetrate the basement
membrane and invade the subepithelial stroma.
Metaplasia: It is reversible change in which one type of differentiated cell is
replaced by another type of differentiated cells (refer pages 44-5). It is a
cellular adaptation that develops in association with tissue damage, repair
and regeneration, e.g., gastroesophageal reflux damages the squamous
epithelium of the esophagus which is replaced by glandular (gastric or
intestinal) epithelium, columnar epithelium of endocervix is replaced by
stratified squamous epithelium. Malignancy may develop in these
metaplastic epithelium.In concis form for exams