What Causes Breast Cancer?
What is Breast Cancer?
Breast cancer is the most common cancer occurring in women (excluding
cancers of the skin) and the second most common cause of death from cancer
in women after lung cancer. Men can also develop breast cancer, but male
breast cancer is rare, accounting for less than 1% of all breast cancer
cases. If diagnosed at an early stage, breast cancer has an encouraging
cure rate: up to 97% of women diagnosed with localized breast cancer will
survive five years after their diagnosis. Even if the cancer is found at
a more advanced stage, new therapies have enabled many people with breast
cancer to experience a good quality of life.
The breast is comprised
mainly of fatty tissue. Within this tissue is a network of lobes, which
are made up of tiny, tube-like structures (called lobules) that contain
milk glands. Tiny ducts connect the glands, lobules, and lobes and carry
the milk from the lobes to the nipple, located in the middle of the areola
(darker area that surrounds the nipple of the breast). Blood and lymph
vessels run throughout the breast; blood nourishes the cells, and the
lymph system drains bodily waste products.
The main forms of breast cancer are:
- Invasive ductal carcinoma — This type of breast
cancer develops in the milk ducts and accounts for about 79 percent
of cases. It can break through the duct wall and invade the breast's
fatty tissue, then metastasize (spread) to other parts of the body through
the bloodstream or lymphatic system.
- Invasive lobular carcinoma — This type of
breast cancer accounts for about 10 percent of cases and originates
in the breast's milk-producing lobules. It also can spread to the breast's
fatty tissue and other places in the body.
- Medullary, mucinous and tubular carcinomas —
These are three slow-growing types of breast cancer. Together they represent
about 10 percent of all breast cancers.
- Paget's disease — This type represents about
1 percent of breast cancers. It starts in the milk ducts of the nipple
and can spread to the areola (dark circle around the nipple). Women
who get Paget's disease usually have a history of nipple crusting, scaling,
itching or inflammation.
- Inflammatory carcinoma —This type accounts
for about 1 percent of all cases. Of all breast cancers, inflammatory
carcinoma is the most aggressive and difficult to treat, because it
spreads so quickly.
- Ductal carcinoma in situ (DCIS) — DCIS occurs
when cancer cells fill the ducts but haven't yet spread through the
walls into fatty tissue. Nearly all women diagnosed at this early stage
can be cured. Without treatment, about 25 percent of DCIS cases will
lead to invasive breast cancer within 10 years.
- Lobular carcinoma in situ (LCIS) — LCIS is
less common and less of a threat than DCIS. It develops in the breast's
milk-producing lobules. LCIS doesn't require treatment, but it does
increase a woman's risk of developing breast cancer.
A woman who has breast cancer may have no problems, or she may find a
painless lump in her breast. If women examine their breasts monthly, they
can help find lumps or other changes that a doctor should examine.
Most breast lumps are not cancer, but all lumps should be checked out
by a doctor to be sure. Non cancerous breast lumps may be scar tissue
or cysts (fluid-filled lumps or sacs) or they can be due to normal breast
changes associated with hormone changes or aging.
Symptoms of breast cancer include:
- A lump or thickening in the breast or under the arm
- A clear or bloody discharge from the nipple
- Persistent crusting or scaling of the nipple
- Inverted nipples
- Redness or swelling of the breast
- Dimpling on the breast skin resembling the texture of an orange
- A change in the contours of the breast, such as one being higher
than the other
- A sore or ulcer on the skin of the breast that does not heal
Many cases of breast cancer occur in women with no obvious risk factors.
This means that women need to be alert in watching for possible changes
in their breasts, performing self-examinations, and scheduling clinical
breast examinations and mammograms. It is likely that multiple risk factors
influence the development of breast cancer. Some of these include:
Age. The risk of developing breast cancer increases
as a woman ages, with the majority of breast cancers developing in women
over the age 50. At age 30, a woman's risk of developing breast cancer
is one in 2,525. By age 50, her chances are one in 50, rising to one in
14 by age 70.
Race. Although white women are more likely to develop
breast cancer, black women are more likely to die from the disease. The
reasons for this are unclear and probably involve both socioeconomic and
Previous history of breast cancer. Women who have had
breast cancer in one breast have three to four times the risk of breast
cancer in their opposite breast.
A history of endometrial or ovarian cancer. The development
of these cancers is also associated with exposure to hormones and, therefore,
a woman's risk of breast cancer may also be increased. Some BRCA1 or BRCA2
gene mutations may also increase the risk of both ovarian and breast cancers.
A family history of breast cancer. Women who have a
first-degree relative (mother, sister, daughter) diagnosed with breast
cancer are at increased risk of the disease. More than one first-degree
relative with breast cancer elevates that risk.
A genetic predisposition. Mutations to the BRCA1 or
BRCA2 genes are associated with increased breast cancer risk. Screening
tests are available to test for known mutations to these genes, but are
not recommended for everyone and only following appropriate genetic counseling.
Researchers estimate that breast cancers caused by these genes make up
only 2% to 3% of all breast cancers.
Estrogen exposure. Estrogen is a hormone in women that
controls the development of secondary sex characteristics (such as breast
development). A woman's production of estrogen decreases at menopause.
Doctors think that exposure to estrogen for a long time may increase breast
- A long menstrual history: Women who began menstruating before age
12 or went through menopause after age 55 have a higher risk of breast
cancer because their breast cells have been exposed to estrogen for
longer periods of time.
- Late or no pregnancies: Women who have their first pregnancy after
age 30 or who have never had a full-term pregnancy have a higher risk
of breast cancer. Pregnancy may protect against breast cancer because
it pushes breast cells into their final phase of maturation.
- Estrogen in medication: Recent use of oral contraceptives or hormone
replacement therapy (HRT), or long-term use of HRT, may increase a
woman's risk of breast cancer.
Atypical hyperplasia. This is a condition characterized
by abnormal, but not cancerous, cells. Atypical hyperplasia is a risk
factor of breast cancer.
Lobular carcinoma in-situ. This is associated with an
increased risk of developing a cancer in either breast when found within
an otherwise benign breast biopsy.
Lifestyle factors. As with other types of cancer, studies
continue to show that various habits may contribute to the development
of breast cancer. These include:
- Obesity: According to a new study, being obese or even overweight
increases a woman's risk of breast cancer.
- Lack of exercise: Exercise lowers hormone levels and boosts the
immune system; lack of exercise contributes to obesity.
- Alcohol use: Drinking more than one alcoholic drink per day may
raise the risk of breast cancer.
Radiation. High doses of radiation may increase a woman's
risk of breast cancer. An increased risk of breast cancer has been observed
in long-term survivors of atomic bombs, patients with lymphoma treated
with radiation therapy to the chest, patients undergoing large numbers
of x-rays for tuberculosis or non-malignant conditions of the spine, and
children treated with radiation for tinea capitis (ringworm).
Even though the doctor will tailor the treatment for breast cancer to
the patient's disease and personal situation, there are some general steps
in the logic of treating the disease. Primarily, the initial therapy for
early stage disease is aimed at eliminating any visible tumor. Therefore,
doctors will recommend surgery to remove the tumor with or without radiation
The next step in the management of early stage disease is to reduce the
risk of the disease recurring and to eliminate any cancer cells that may
remain. If a tumor is of a certain size or lymph nodes are involved, the
doctor may recommend additional therapy, such as radiation therapy, chemotherapy,
or hormonal therapy. If the cancer recurs, the patient may choose additional
surgery, depending on where the cancer is found, or a variety of treatments
designed to fight distant metastases.
Generally, the smaller the tumor, the more surgical options a patient
has. The general types of surgery include the following:
- Lumpectomy - A lumpectomy removes the tumor and
a small "clean," or disease-free, margin of tissue around
the tumor. Follow-up radiation therapy is given to the disease site.
- Partial Mastectomy - A partial mastectomy removes
the tumor, an area of normal tissue, and part of the lining over the
chest muscle where the tumor was. This surgery is similar to a lumpectomy.
It is also called a segmental mastectomy and requires follow-up radiation.
- Modified Radical Mastectomy - A modified radical
mastectomy removes the breast, some of the underarm lymph nodes, and
the lining over the chest muscles.
- Total Mastectomy - A total mastectomy removes the
entire breast, leaving the underarm lymph nodes intact. This surgery
is also called simple mastectomy.
- Radical Mastectomy - A radical mastectomy removes
the breast, chest muscles, all lymph nodes under the arm, and additional
fat and skin. It used to be the standard surgical treatment for breast
cancer, but is an uncommon procedure today. About 15% of women who have
had radical mastectomies experience lymphedema, the buildup of fluid
in the lymph system.
Women are encouraged to talk with their doctors about which surgical
option is right for them. More aggressive surgery is not always better
and may result in additional complications.
Choosing Between Lumpectomy and Mastectomy
One advantage of lumpectomy is that it saves the way the breast
looks. A downside is the need for several weeks of radiation after surgery.
But some women who have a mastectomy will still need radiation. For most
women with stage I or II breast cancer, lumpectomy or partial mastectomy
(along with radiation) is as good as mastectomy. There is no difference
in the survival rates of women treated with these 2 methods. Other factors,
though, can affect which type of surgery is best for you. And lumpectomy
is not an option for all women with breast cancer. Your doctor can tell
you if there are reasons why a lumpectomy is not right for you.
Possible side effects of mastectomy and lumpectomy include infection
and blood or fluid collecting at the place where the incision is made.
If lymph nodes are removed, there could be other side effects as well
such as swelling of the arm (lymphedema).
Radiation Therapy and Chemotherapy are often used after
lumpectomy or mastectomy to make sure that all the cancer cells are destroyed
and do not grow back.
- Radiation therapy almost always is recommended after lumpectomy to
destroy any cancer cells left behind and to prevent the cancer from
returning. Without radiation therapy, the odds of the cancer returning
increase by about 25 percent.
- The need for Chemotherapy depends on how much the cancer has spread.
In some cases, chemotherapy will be recommended before surgery to shrink
a large tumor so that it can be removed more easily. Chemotherapy is
almost always necessary if cancer recurs. A form of chemotherapy called
hormonal chemotherapy usually is recommended when the pathology report
shows that the cancer is estrogen-receptor positive.
After the first course of treatment is finished, it is very important
to keep all follow-up visits to your doctor. Be sure and tell the doctor
about any symptoms or side effects that concern you.
Lymphedema is a swelling of the arm caused by fluid build up that may
occur after treatment for breast cancer. It's hard to tell which women
will develop lymphedema. It can happen right after surgery, or months
or even years later.
With care, lymphedema can often be avoided or kept under control. Injury
or infection of the arm on the affected side can cause lymphedema or make
it worse. Tell your doctor right away about any swelling, tightness, or
injury to the hand or arm. There are ways to help prevent problems. More
information about lymphedema is available through our toll-free number
or on our Web site.
Treatment for breast cancer can affect the pleasure from touching the
breast. In a reconstructed breast, the feeling of pleasure from touching
the nipple is largely lost because a preserved or rebuilt nipple has much
less feeling than a natural one. The skin of the breast itself may be
less sensitive, too. Some feeling can return after time, though.
About Breast Forms and Bras
Some women who have had a mastectomy might choose breast forms
instead of reconstruction. Your doctor will tell you when you are ready
to be fitted for a permanent form. Prices of forms vary quite a bit.
Take time to shop for one that looks good and fits well.
The right bra for you may very well be the one you have
always worn. You can often have your usual bra adapted for a breast
form. Be sure to check your insurance to see what is covered and how
to file a claim. Also, ask your doctor to write prescriptions for your
form and any special bras. When buying the forms or bras, have the bills
Be aware that if you submit an insurance claim for a form
or a bra, the company might not also cover reconstruction if you decide
you want this procedure in the future. Get all the facts before turning
in any claims.
In the past, many doctors advised breast cancer survivors
not to become pregnant for at least 2 years after treatment. Although
only a few studies have been done, nearly all have found that pregnancy
does not increase the risk of the cancer coming back after successful
treatment. If you are thinking about getting pregnant, be sure to
discuss the issue with your doctor. Sometimes counseling can help
you sort out the complex issues about motherhood and breast cancer
National Organizations and Web Sites
Encore Plus Program of the YWCA
Office of Women's Health Initiatives
Telephone: 800-953-7587 or 202-467-0801
Call to find a program in your area.
National Breast Cancer Coalition
1101 17th Street, NW, Suite 1300Washington, DC 20036
Telephone: 800-622-2838 or 202-296-7477
National Cancer Institute (NCI)
Susan G. Komen Breast Cancer Foundation
Telephone: 800-IM-AWARE or 1-800-462-9273
Y-ME National Breast Cancer Hotlines
Telephone: 1-800-221-2141 (English), 1-800-986-9505
Centers for Disease Control and Prevention (CDC) DES Update