What is breast cancer?
To combat breast cancer effectively, it's important to first
understand just what breast cancer is, how it occurs, the stages
of the disease, and how these affect you. Equally important is
dispelling many of the myths and misunderstandings surrounding
breast cancer and women's risk of the disease.
The anatomy of the breast
Let's first examine the anatomy of the breast. The breast, or
mammary gland, contains lobules, glands which
produce milk, ducts which connect the lobules to the
nipple, and stroma, fatty tissue and connective tissue
surrounding the ducts and lobules; blood vessels, and lymphatic
vessels. As we'll see a little later, most breast cancers
begin in the ducts (atypical ductal hyperplasia), some
in the lobules (lobular carcinoma in situ), and the rest
in other tissues.
Image by illustrator Susan Spangler appears with the artist's
National Cancer Institute, U.S. National Institutes of Health.
Lymphatic vessels are quite similar to blood vessels
except that rather than carrying blood, lymphatic vessels carry
lymph, a clear fluid that contains tissue fluid, waste
products, and immune system cells. Small, bean-shaped collections
of immune system cells found along lymphatic vessels, lymph
nodes can be invaded by cancer cells which have entered lymphatic
vessels and metastasized (spread) to involve them as well.
Most lymphatic vessels in the breast connect to axillary
lymph nodes under the arm, while others connect to internal
mammary nodes in the chest or to supra- or infraclavicular
nodes above or below the clavicle (collarbone),
What is breast cancer?
As with all cells in the human body, breast cells have a life
cycle during which they grow, divide, produce more cells and eventually
die. Cells' life cycle is controlled by genes in their nucleus.
Under normal conditions, genes are able to effectively regulate
this cellular life cycle. However, when genes develop an abnormality,
the life cycle is affected and some cells may continue to divide
even when new cells are not needed, forming a mass of new issue
called a growth or tumor.
Tumors may be benign or malignant.
Benign tumors are not cancerous and can be removed.
While they are abnormal growths, benign tumors such as fibroadenomas
or papillomas are not cancerous and cannot spread beyond
the breast to affect other organs. Such benign growths are not
The majority of breast lumps are benign and are often the result
of fibrocystic changes that may cause swelling and pain. Such
changes are quite common just before a woman's menstrual period
is about to begin, with breasts feeling nodular or lumpy. This
can occasionally be accompanied by a clear or slightly cloudy
Malignant tumors, on the other hand, are cancer. Breast
cancer, therefore, is an uncontrolled growth of breast cells.
Cells in such tumors divide without any rhyme or reason, invading
nearby tissues and organs. Through a process known as metastasis,
cancer cells can also break through normal breast tissue to other
parts of the body.
For instance, breast cancer may metastasize from breast tissue
to reach the axillary lymph nodes under the arm. When this happens,
cancer cells may continue to grow, causing the underarm lymph
nodes to swell. Once breast cancer cells have spread to the axillary
lymph nodes, they are more likely to metastasize to other organs
of the body as well. This is why, when choosing a breast cancer
treatment, it's especially important to find out if breast cancer
has spread to the axillary lymph nodes.
Let's examine the types of breast cancer, since an understanding
of the terms used will help you learn how cancer patients vary
in their prognosis and treatment.
Types of breast cancers
Because nearly all breast cancers begin in the ducts or lobules—glandular
tissues—they are called adenocarcinomas. Adenocarinomas
may be classed as ductal carcinomas or lobular carcinomas.
Confined to the immediate area where it began, in situ
refers to an early stage of cancer. When used in reference to
breast cancer, in situ denotes cancer that remains confined to
ducts (ductal carcinoma in situ) or lobules (lobular
carcinoma in situ). In other words, this cancer has not invaded
fatty tissues in the breast, nor has it metastasized to other
organs in the body.
Also known as intraductal carcinoma and comprising approximately
20 percent of new breast cancer cases, ductal carcinoma in
situ (DCIS) is the most common type of non-invasive breast
cancer. In DCIS, cancer cells are inside the ducts but have not
spread beyond the duct walls into surrounding breast tissue. Mammography
is the most effective and reliable means of finding DCIS early.
What's more, nearly all women diagnosed at this early stage can
be cured. Yet, an important distinction the pathologist will need
to make is noting whether tumor necrosis, an area of
dead or degenerating cancer cells, exists. If necrosis is present,
the tumor is considered more aggressive and is described as comedocarcinoma.
Although sometimes classified as a non-invasive breast cancer,
lobular carcinoma in situ (LCIS) is not a true cancer.
LCIS begins in the milk-producing glands, but does not spread
beyond the wall of the lobules. Despite many breast cancer specialists'
belief that LCIS itself does not become an invasive cancer, it
should be noted that women with LCIS do have an increased risk
of developing an invasive breast cancer in the same or even in
the opposite breast. Therefore, women with LCIS should undergo
a physical exam 2 to 3 times per year, in addition to a yearly
The most common breast cancer, comprising approximately 80 percent
of invading breast cancers, infiltrating (or invasive) ductal
carcinoma (IDC) begins in the duct of the breast. Called
invasive because it has broken through the wall of the duct and
invaded nearby fatty breast tissue, IDC can metastasize to other
parts of the body through the lymphatic system and bloodstream.
Beginning in the lobules and metastasizing to other parts of
the body, infiltrating (or invasive) lobular carcinoma
(ILC) comprises about 5 percent of all invasive breast cancers
and is harder to detect through mammography
than infiltrating ductal carcinoma.
A rare type of invasive breast cancer that constitutes between
1 and 3 percent of all breast cancers, inflammatory breast
cancer starts in the breast ducts and spreads to the skin
of the nipple and then to the areola (the dark circle
around the nipple).
Developing under the connective tissue of the breast, phyllodes
tumor is extremely rare. Although benign in most cases, phyllodes
(also spelled phylloides) can also, on rare occasions,
be malignant. When benign, phyllodes are removed along with a
narrow margin of normal breast tissue. In cases of malignant phyllodes,
the tumor is removed along with a wider margin of normal breast
tissue and may also be removed by mastectomy.
Who's at risk?
There are identified risk factors that may place certain women
at significantly greater risk of breast cancer. In addition, having
one risk factor—or even several—does not necessarily
mean you will develop breast cancer. Understanding risk factors
places you in a far better position to understand and manage your
risk profile and to discuss it with your doctor. Risk factors
Every woman is at some risk of developing breast cancer—that's
a sad fact of being a woman. Although breast cancer does affect
men, it is 100 times more common among women. This is because,
obviously, women have more breast cells than men do. It may also
be due in part to the fact that women's breast cells are constantly
exposed to the growth-promoting effects of female hormones.
According to Breastcancer.org,
the chances of developing breast cancer before the age of 39 are
slim indeed. From birth to age 39, 1 in 231 (less than 0.5%) women
will develop breast cancer. However, from ages 40 to 59, risk
increases to 1 in 25, or 4%, and from ages 60 to 79, the chance
of developing breast cancer is 1 in 15, nearly 7%. Put another
way, this means that about 18 percent of cancer diagnoses are
among women in their 40s and that about 77 percent of women are
in their 50s when they are diagnosed.
The Canadian Cancer Society states that:
- Out of 1,000 women aged 30 about four will be expected
to develop breast cancer within the next 10 years;
- Out of 1,000 women aged 50 about twenty will be expected
to develop breast cancer within the next 10 years;
- Out of 1,000 women aged 70 about thirty will be expected
to develop breast cancer within the next 10 years;
are Breast Cancer Risk Factors? Canadian Cancer Society.
Women who have already had breast cancer are 3 to 4 times more
likely to develop new occurrences of the disease. Risk is estimated
at 1 percent per year, which means that over the course of ten
years, if a woman has had breast cancer before, she has a 10 percent
chance of developing it again. Medications, however, can help
reduce this risk.
Women with a family history of breast cancer are also at increased
risk of the disease. This is especially true if a direct first-degree
relative (mother, daughter, sister) on either her mother or father's
side has had breast cancer: risk nearly doubles when this is the
case. Risk is also higher among women belonging to families in
which multiple generations of family members were affected by
breast or ovarian cancer, in which a family member was diagnosed
with breast cancer at a young age (under the age of 50), or in
which a family member (male or female) was affected by breast
cancer in both breasts.
Consider the following:
Your risk of developing breast cancer is increased if:
- You have 2 or more relatives with breast or ovarian cancer.
- Breast cancer occurs before age 50 in a relative (mother,
sister, grandmother or aunt) on either side of the family.
The risk is higher if your mother or sister has a history
of breast cancer.
- You have relatives with both breast and ovarian
- You have one or more relatives with two cancers (breast
and ovarian, or two different
- You have a male relative (or relatives) with breast cancer.
- You have a family history of breast or ovarian
cancer and Ashkenazi Jewish heritage.
- Your family history includes a history of diseases associated
with hereditary breast cancer such as Li-Fraumeni or Cowdens
are the Risk Factors for Breast Cancer? American Cancer
Society, Inc. (2004)
One should also not assume that breast cancer runs only in families
and that if no one in her family is affected, she will likely
not develop breast cancer. The truth is that nearly 80 percent
of women who develop breast cancer have no known family history
of the disease. Of women who do have a family history of breast
cancer, their personal risk may be increased slightly, significantly,
or not at all.
Recent evidence shows that about 10 percent of breast cancer
cases are hereditary as the result of gene mutations such as those
affecting the BRCA1 and BRCA2 genes. Normally, these genes help
prevent breast cancer by making proteins that keep cells from
growing abnormally. However, if a mutated gene is inherited from
either parent, a woman's risk of breast cancer increases: women
with an inherited BRCA1 or BRCA2 mutation have a 35 to 85 percent
chance of developing breast cancer.
Genetic evaluation typically includes detailed assessment of
a woman's family history, and genetic counseling may include blood
tests for the breast cancer gene mutations mentioned above. While
such tests do not predict whether a woman will develop breast
cancer, they do indicate whether she has inherited a BRCA1 or
a BRCA2 mutation.
Many women who inherit such breast cancer gene mutations never
develop breast cancer: of women with a BRCA1 (located on chromosome
17) or BRCA2 (located on chromosome 13) inherited genetic abnormality,
40 to 80 percent will develop breast cancer over their lifetime
while 20 to 60 percent will not. It also follows that a woman
who has not inherited a gene mutation from either parent cannot
pass it on to her children.
Caucasian women are at slightly higher risk of developing breast
cancer than Black women. Yet Black women are more likely to die
of breast cancer because their cancers are often diagnosed later
and at an advanced stage. There is also some speculation that
black women may have more aggressive tumors. Asian, Hispanic/Latino,
and Aboriginal/First Nations women appear to have a lower risk
of developing breast cancer. Also worth noting is that hereditary
breast cancer is more common in Jewish women than in non-Jewish
Prolonged, uninterrupted exposure to estrogen
Breast cell growth is stimulated by the presence of estrogen,
whether estrogen produced naturally in the body, or estrogen introduced
as part of estrogen replacement
therapy. Early menarche (menstruation which began
before age 12) and late menopause (menopause after age 55) are
each synonymous with a greater number of years during which the
body produced estrogen. As a result, women who got their period
early or who entered menopause late are at increased risk of developing
Post-menopausal women who have been prescribed estrogen alone
or in combination with progesterone for periods of five years
or longer are also shown to be at increased risk for breast cancer.
It's also been suggested that estrogen and progesterone combined
may increase the risk of dying of breast cancer.
Women who have had their first full-term pregnancy after the
age of 30 are also at increased risk because their bodies have
had more years of producing estrogen without breaks from regular
Obesity is associated
with an increased risk of breast cancer, particularly in post-menopausal
women. Women who are overweight experience increased production
of estrogen outside their ovaries, and this in turn contributes
to increased levels of estrogen throughout the body.
Alcohol consumption in excess of two drinks per week also appears
to increase risk since alcohol limits the liver's ability to regulate
blood estrogen levels. Research suggests that those who have 2
to 5 drinks daily are 1.5 times more likely to develop breast
cancer than those who do not drink. What's more, alcohol is also
known to increase the risk of developing cancers in the mouth,
throat, and esophagus.
One drink is defined as 1½ fluid ounces (45 mL) of 80-proof
spirits (i.e. bourbon, Scotch, vodka, gin, etc.) 1 fluid ounce
(30 mL) 100-proof spirits, 4 fluid ounces (125 mL) wine, or
12 fluid ounces (355 mL) beer.
Changes in breast cells
Changes in breast cells, identified when a breast
biopsy is performed, can also increase risk of breast cancer.
Such cellular changes may be identified as being either atypical
ductal hyperplasia or lobular carcinoma in situ.
Atypical ductal hyperplasia refers to overproduction of cells
lining the breast ducts, whereas lobular carcinoma in situ refers
to an uncontrolled growth of lobular cells.
Previous breast biopsy
Women whose earlier breast biopsies
showed proliferative breast disease without atypia
or usual hyperplasia are 1.5 to 2 times more likely to
develop breast cancer than other women, while those whose previous
biopsies showed a result of atypical hyperplasia are 4 to 5 times
more likely to develop breast cancer. Biopsy
specimens diagnosed as fibrocystic changes without proliferative
breast disease do not affect breast cancer risk.
Previous breast radiation
Those women who, whether as children or young adults, have had
previous radiation therapy to the chest area as treatment for
cancer (e.g. Hodgkin's lymphoma) have a significantly increased
risk of breast cancer. Some reports have suggested the risk is
12 times greater than normal, although the risk varies depending
on the age of the patient at the time of radiation treatment:
younger patients have a higher risk. However, if chemotherapy
was given, risk is reduced because chemotherapy often stops ovarian
There is yet another benefit to regular exercise: recent studies
show that strenuous exercise in young women may provide long-term
protection against breast cancer. In addition, moderate to strenuous
physical activity in adulthood is also believed to lower breast
There are studies which suggest that breastfeeding may slightly
decrease breast cancer risk, particularly if breastfeeding continues
for 1.5 to 2 years. Yet other studies suggest there is no correlation
between breastfeeding and breast cancer risk.
Even if you believe you are at high risk of developing breast
cancer, do not resign yourself to thinking there is little or
nothing you can do. It's true that there is nothing that can be
done to prevent breast cancer from occurring, but there are things
that may be done to reduce one's risk. Lifestyle changes such
as stopping smoking, exercising regularly, minimizing alcohol
consumption, and taking medications such as tamoxifen (Nolvadex)
can all help reduce the risk of breast cancer in women at high
risk. In cases of very high risk, prophylactic mastectomies
may be recommended. Be sure to discuss your concerns with your
doctor before making any assumptions about your personal risk.
Myths about breast cancer
Breast cancer is often believed to affect only older women. As
we've seen, breast cancer can affect women at any age, although
having one or more of the above-mentioned risk factors does not
necessarily imply that a woman will develop breast cancer.
Another common misconception is that use of antiperspirants or
increases breast cancer risk. There is no evidence to support
that antiperspirants increase breast cancer risk. Higher-dose
pills of yesteryear were associated with a slightly increased
risk of breast cancer. Today's birth control pills, however, contain
estrogen and progesterone in low doses and have not been associated
with increased risk of breast cancer; they have been clinically
proven to provide some protection against ovarian
While monthly breast self-examination is
recommended and ensures that a woman becomes familiar with the
texture of her own breasts, BSE is not viewed as the best way
to safeguard against or to detect breast cancer. By the time breast
cancer can be felt in BSE, tumors are usually larger in size than
those found through mammography. Therefore, the most effective
and reliable way to detect breast cancer is through high-quality,
film-screen mammography. Tactile breast
examination by a doctor or gynecologist is said to find about
25 percent of breast cancers, while 35 percent are found through
mammography alone. The best course
of action is to use BSE or examination by your doctor (CBE)
in combination with mammography as doing so is said to find 40
percent of breast cancers.
Not all breast cancers are fatal. In fact, the majority of cases
(80 percent) of breast cancer have no signs of metastases. In
other words, these patients' cancers did not spread beyond the
breast and nearby lymph nodes. Survival rates for such cases are
also encouraging: 80 percent of these cases live at least 5 years—most
longer, and many much longer. Even in cases where metastases did
occur, life expectancy and prognosis are good.