Causes
With the exception of the rare 'clear
cell' cervical cancers, nearly all
primary cervix cancers are caused by the
wart virus. The wart virus is also
called Human Papilloma Virus (HPV).
There are about 100 different types of
HPV of which about 12 are important.
Each type of HPV is assigned a number
and types 16, 18, 31, 33, 39, 45, 51,
52, 56, 58, 59, and 68 are the most
important. In the UK about 75% of
cervical cancers are caused by type 16
and 18.The wart
virus can get into the cervix at an area
called the transformation zone where one
type of cell (called squamous cell)
changes to another type of cell (called
columnar cell). The genetic material of
the wart virus (DNA) gets incorporated
into the DNA of the human cell. This
wart virus DNA produces one of two
proteins called E6 or E7 that interferes
with the normal cervix cell regulation
leading to cancer.
There are a number of
factors that increase the risk of the
wart virus getting incorporated into the
cells of the cervix. Increased exposure
to the wart virus increases the risk of
cervical cancer. This is why a woman who
has more sexual partners or other
sexually transmitted diseases has a
higher chance of developing cervical
cancer. Women who have partners who have
had many sexual partners also have an
increased risk of cervical cancer.
Local lack of immunity
in the cervix increases the risk of the
wart virus getting into cervix cells.
Some studies have demonstrated a
reduction in the number of immune cells
called Languerhan cells, CD4 cells, and
CD8 cells in the cervix of women with
cervical cancer. Women with
immunodeficient medical conditions (e.g.
AIDS, steroid usage, organ transplant
treatment) have an increased risk of
cervical cancer. There is an association
with smoking and cervical cancer which
may be related to local immunodeficiency
in the cervix.
The process of damaged
DNA caused by the wart virus causes
something called CIN (Cervical
Intra-epithelial Neoplasia). Other terms
include dysplasia and SIL
(squamous intraepithelial lesion). When
this happens to the columnar cells it is
called CGIN (Cervical Glandular
Intra-epithelial Neoplasia) or AIS
(Adenocarcinoma In-Situ). CIN can
sometimes (but not always) be detected
on a smear test and when this occurs it
is called dyskaryosis.
The abnormal cells in
CIN are not cancerous because they have
not invaded an area of tissue called the
basement membrane. Sometimes CIN goes
away on it's own untreated which is why
CIN I is treated conservatively in the
first instance by most gynaecologists.
The risk of transformation with time
from CIN II or CIN III to cancer are
high enough to warrant
treatment
for CIN.
