Cervical
Intraepithelial
Neoplasia
Cervical intraepithelial neoplasia, or CIN, is the abnormal
growth of
precancerous
cells in the
cervix. Most
cases of CIN
remain
stable, or
are
eliminated
by the
host's
immune
system
without
intervention.
However a
small
percentage
of cases
progress to
become
cervical
cancer,
usually
cervical
squamous
cell
carcinoma,
or SCC. The
major cause
of CIN is
infection
with the
sexually
transmitted
human
papillomavirus
(HPV),
usually the
high-risk
HPV types 16
or 18.
The earliest microscopic change corresponding to CIN is
dysplasia of
the
epithelial
or surface
lining of
the cervix,
which is
essentially
undetectable
by the
woman.
Cellular
changes
associated
with HPV
infection,
such as
koilocytes,
are also
commonly
seen in CIN.
It is
usually
discovered
by a
screening
test, the
Papanicolaou
or "pap"
smear. The
purpose of
this test is
to diagnose
the disease
early, while
it has not
yet
progressed
to invasive
carcinoma,
and thus is
easy to
cure. Though
epithelial
dysplasia
may regress
spontaneously,
persistent
lesions must
be removed,
either with
surgery,
chemical
burning,
heat
burning,
burning with
laser, or
freezing (cryotherapy).
Grades
CIN has three distinct grades:
* CIN1 (Grade I), the least risky type, represents only
mild
dysplasia,
or abnormal
cell growth
and is
considered a
low grade
squamous
intraepithelial
lesion (LGSIL).
It is
confined to
the basal
1/3 of the
epithelium.
* CIN2 (Grade II), as well as CIN III, are considered
high grade
squamous
intraepithelial
lesions (HSIL).
CIN2
represents
moderate
dysplasia,
and is
confined to
the basal
2/3 of the
epithelium
* CIN3 (Grade III): In this lesion, severe dysplasia
spans
greater than
2/3 of the
the entire
epithelium,
and may
involve the
full
thickness.
This lesion
may also be
referred to
as cervical
carcinoma in
situ.
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