Causes of breast cancer

Breast cancer is a kind of cancer
that develops from breast cells.
Breast cancer usually starts off in
the inner lining of milk ducts or
the lobules that supply them with
milk. A malignant tumor can
spread to other parts of the body.
A breast cancer that started off in
the lobules is known as lobular
carcinoma, while one that
developed from the ducts is called
ductal carcinoma.
The vast majority of breast cancer
cases occur in females. This article
focuses on breast cancer in women.
Click here to read about breast
cancer in men (male breast cancer).
Breast cancer is the most common
invasive cancer in females
worldwide. It accounts for 16% of all
female cancers and 22.9% of
invasive cancers in women. 18.2% of
all cancer deaths worldwide,
including both males and females,
are from breast cancer.
Breast cancer rates are much higher
in developed nations compared to
developing ones. There are several
reasons for this, with possibly life-
expectancy being one of the key
factors - breast cancer is more
common in elderly women; women
in the richest countries live much
longer than those in the poorest
nations. The different lifestyles and
eating habits of females in rich and
poor countries are also contributory
factors, experts believe.
According to the National Cancer
Institute, 232,340 female breast
cancers and 2,240 male breast
cancers are reported in the USA
each year, as well as about 39,620
deaths caused by the disease.
The anatomy of a female
breast
1. Chest wall. 2. Pectoralis muscles.
3. Lobules (glands that make milk).
4. Nipple surface. 5. Areola. 6.
Lactiferous duct tube that carries
milk to the nipple. 7. Fatty tissue. 8.
Skin.
A mature human female's breast
consists of fat, connective tissue and
thousands of lobules - tiny glands
which produce milk. The milk of a
breastfeeding mother goes through
tiny ducts (tubes) and is delivered
through the nipple.
The breast, like any other part of the
body, consists of billions of
microscopic cells. These cells
multiply in an orderly fashion - new
cells are made to replace the ones
that died. In cancer, the cells
multiply uncontrollably, and there
are too many cells, progressively
more and more than there should
be.
Cancer that begins in the lactiferous
duct (milk duct), known as ductal
carcinoma, is the most common
type. Cancer that begins in the
lobules, known as lobular
carcinoma, is much less common.
What is the difference
between invasive and non -
invasive breast cancer ?
Invasive breast cancer - the cancer
cells break out from inside the
lobules or ducts and invade nearby
tissue. With this type of cancer, the
abnormal cells can reach the lymph
nodes, and eventually make their
way to other organs (metastasis),
such as the bones, liver or lungs.
The abnormal (cancer) cells can
travel through the bloodstream or
the lymphatic system to other parts
of the body; either early on in the
disease, or later.
Non-invasive breast cancer - this is
when the cancer is still inside its
place of origin and has not broken
out. Lobular carcinoma in situ is
when the cancer is still inside the
lobules, while ductal carcinoma in
situ is when they are still inside the
milk ducts. "In situ" means "in its
original place". Sometimes, this type
of breast cancer is called "pre-
cancerous"; this means that
although the abnormal cells have
not spread outside their place of
origin, they can eventually develop
into invasive breast cancer.
What are the signs and
symptoms of breast cancer ?
A symptom is only felt by the
patient, and is described to the
doctor or nurse, such as a headache
or pain. A sign is something the
patient and others can detect, for
example, a rash or swelling.
The first symptoms of breast cancer
are usually an area of thickened
tissue in the woman's breast, or a
lump. The majority of lumps are not
cancerous; however, women should
get them checked by a health care
professional.
According to the National Health
Service, UK, women who detect any
of the following signs or symptoms
should tell their doctor:
A lump in a breast
A pain in the armpits or breast
that does not seem to be
related to the woman's
menstrual period
Pitting or redness of the skin of
the breast; like the skin of an
orange
A rash around (or on) one of
the nipples
A swelling (lump) in one of the
armpits
An area of thickened tissue in a
breast
One of the nipples has a
discharge; sometimes it may
contain blood
The nipple changes in
appearance; it may become
sunken or inverted
The size or the shape of the
breast changes
The nipple-skin or breast-skin
may have started to peel, scale
or flake
What are the causes of
breast cancer ?
Experts are not sure what causes
breast cancer. It is hard to say why
one person develops the disease
while another does not. We know
that some risk factors can impact on
a woman's likelihood of developing
breast cancer.
Getting older - the older a
woman gets, the higher is her
risk of developing breast
cancer; age is a risk factor.
Over 80% of all female breast
cancers occur among women
aged 50+ years (after the
menopause ).
Genetics - women who have a
close relative who has/had
breast or ovarian cancer are
more likely to develop breast
cancer. If two close family
members develop the disease,
it does not necessarily mean
they shared the genes that
make them more vulnerable,
because breast cancer is a
relatively common cancer.
The majority of breast cancers
are not hereditary.
Women who carry the BRCA1
and BRCA2 genes have a
considerably higher risk of
developing breast and/or
ovarian cancer. These genes
can be inherited. TP53, another
gene, is also linked to greater
breast cancer risk.
A history of breast cancer -
women who have had breast
cancer, even non-invasive
cancer, are more likely to
develop the disease again,
compared to women who have
no history of the disease.
Having had certain types of
breast lumps - women who
have had some types of benign
(non-cancerous) breast lumps
are more likely to develop
cancer later on. Examples
include atypical ductal
hyperplasia or lobular
carcinoma in situ.
Dense breast tissue - women
with more dense breast tissue
have a greater chance of
developing breast cancer.
Estrogen exposure - women
who started having periods
earlier or entered menopause
later than usual have a higher
risk of developing breast
cancer. This is because their
bodies have been exposed to
estrogen for longer. Estrogen
exposure begins when periods
start, and drops dramatically
during the menopause.
Obesity - post-menopausal
obese and overweight women
may have a higher risk of
developing breast cancer.
Experts say that there are
higher levels of estrogen in
obese menopausal women,
which may be the cause of the
higher risk.
Height - taller-than-average
women have a slightly greater
likelihood of developing breast
cancer than shorter-than-
average women. Experts are
not sure why.
Alcohol consumption - the
more alcohol a woman
regularly drinks, the higher her
risk of developing breast
cancer is. The Mayo Clinic says
that if a woman wants to drink,
she should not exceed one
alcoholic beverage per day.
Radiation exposure -
undergoing X-rays and CT
scans may raise a woman's risk
of developing breast cancer
slightly. Scientists at the
Memorial Sloan-Kettering
Cancer Center found that
women who had been treated
with radiation to the chest for a
childhood cancer have a higher
risk of developing breast
cancer .
HRT (hormone replacement
therapy) - both forms,
combined and estrogen-only
HRT therapies may increase a
woman's risk of developing
breast cancer slightly.
Combined HRT causes a higher
risk.
Certain jobs - French
researchers found that women
who worked at night prior to a
first pregnancy had a higher
risk of eventually developing
breast cancer .
Canadian researchers found
that certain jobs, especially
those that bring the human
body into contact with possible
carcinogens and endocrine
disruptors are linked to a
higher risk of developing breast
cancer . Examples include bar/
gambling, automotive plastics
manufacturing, metal-working,
food canning and agriculture.
They reported their findings in
the November 2012 issue of
Environmental Health.
Cosmetic implants may
undermine breast cancer
survival - women who have
cosmetic breast implants and
develop breast cancer may
have a higher risk of dying
prematurely form the disease
compared to other females,
researchers from Canada
reported in the BMJ (British
Medical Journal) (May 2013
issue).
The team looked at twelve
peer-reviewed articles on
observational studies which
had been carried out in
Europe, the USA and Canada.
Experts had long-wondered
whether cosmetic breast
implants might make it harder
to spot malignancy at an early
stage, because they produce
shadows on mammograms.
In this latest study, the authors
found that a woman with a
cosmetic breast implant has a
25% higher risk of being
diagnosed with breast cancer
when the disease has already
advanced , compared to those
with no implants.