Cancer is a group of diseases characterized by uncontrolled growth of
tissue cells in the body and the invasion by these cells into nearby
tissue and migration to distant sites.
Cancer results from alterations (mutations) in genes that make up DNA, the
master molecule of the cell. Genes make proteins, which are the ultimate
workhorses of the cells, responsible for the many processes that permit
humans to breathe, think, and move, among other functions. Some of these
proteins control the orderly growth, division, and reproduction of normal
tissue cells. Gene mutations can produce faulty proteins, which in turn
produce abnormal cells that no longer divide and reproduce in an orderly
manner. These abnormal cells divide uncontrollably and eventually form a
new growth known as a tumor or neoplasm. A healthy immune system can
usually recognize neoplastic cells and destroy them before they divide.
However, mutant cells may escape immune detection and become tumors or
Studies of the origins of cancer have shown that a combination of genetic
influences and environmental causes over time triggers gene mutations,
which may explain why most cancers are seen in adults of middle age or
older (60%) and cancer is rare children. Many cancers have been shown to
result from exposure to environmental toxins (carcinogens) and related
alterations in DNA. Faulty DNA can also be inherited, predisposing an
individual to develop cancer, although fewer than 10 percent of cancers
are purely hereditary. Hereditary links have been shown in cancers of the
breast, colon, ovaries, and uterus. Inherited physiological traits can
also contribute to cancer, such as inheriting fair skin increasing the
risk of skin cancer, but only if accompanied by prolonged exposure to
Tumors can be benign or malignant. A benign tumor is not cancer. It is
slow growing, does not invade surrounding tissue, and once removed, does
not usually recur. A malignant tumor is cancerous. It invades surrounding
tissue and spreads to nearby or distant organs (metastasis). If the cancer
cells have spread to surrounding tissue, even after the malignant tumor is
removed, it will typically recur.
Cancer falls into several general categories:
The most common cancers affecting adults are cancer of the skin, lung,
colon, breast, and prostate. Cancer of the kidneys, ovaries, uterus,
pancreas, bladder, rectum, and the leukemias and lymphomas are among the
12 major cancers affecting Americans of all ages. Although children and
adolescents do develop solid tumors, the most common high-risk cancers
among children are:
Childhood cancer is rare, occurring in about 14 in 100,000 children in the
United States each year. However, in the entire U.S. population, one of
every four deaths is from cancer, second only to deaths from heart
disease. About 1.2 million cancer cases are diagnosed annually and more
than 500,000 die, of whom 2,700 are children or adolescents.
Causes and symptoms
Genetic predisposition, environmental causes, and individual developmental
problems are responsible for most childhood cancer. The presence of other
disorders, such as
, has also been shown to be
associated with cancer in children. The major risk factors that apply to
adult cancer are tobacco, alcohol, sexual and reproductive behavior, and
occupation, none of which increases risk in children. Other well-known
risk factors, such as
history, infectious agents, diet, environmental toxins, and pollution,
can apply equally to children.
Approximately 80 to 90 percent of lung cancer cases occur in smokers.
is also the leading cause of bladder cancer and has been shown to
contribute to cancers of the upper respiratory tract, esophagus, larynx,
kidney, pancreas, stomach, and possibly breast as well. Second-hand smoke
(passive smoking) has been shown to increase cancer risk in children and
adults who live with smokers.
Cancer deaths worldwide can be traced to viruses, bacteria, or parasites.
Epstein-Barr virus (EBV), for example, is associated with lymphoma, the
hepatitis viruses are associated with liver cancer, HIV is associated with
Kaposi's sarcoma, and the bacteria
is associated with stomach cancer.
Certain cancers such as breast, colon, ovarian, and uterine cancer recur
generation after generation in some families. Eye cancer (
), a type of colon cancer, and early-onset breast cancer have been shown
to be linked to the inheritance of specific genes.
Radiation is believed to cause 1 to 2 percent of all cancer deaths.
Ultraviolet radiation from the sun accounts for a majority of melanoma
deaths. Other sources of radiation are x-rays, radon gas, and ionizing
radiation from nuclear material.
Studies have established links between environmental toxins, such as
asbestos, and cancer. Chlorination of water may account for a small rise
in cancer risk. However, the main danger from pollutants occurs when toxic
industrial chemicals are released into the surrounding environment. As of
2004 an estimated 1 percent of cancer deaths are believed to be due to
air, land, and water pollution.
Cancer is a progressive disease that goes through several stages, each
producing a number of symptoms. Early symptoms can be produced by the
growth of a solid tumor in an organ or gland. A growing tumor may press on
nearby nerves, organs, and blood vessels, causing
and pressure that may be the first warning signs of cancer. Other
symptoms can include sores that do not heal, growths on the skin or below
the skin, unusual bleeding, difficulty digesting food or swallowing, and
changes in bowel or bladder function.
can be present as well as fatigue and weakness.
Despite the fact that there are hundreds of different types of cancer,
each producing different symptoms, the American Cancer Society has
established the following seven symptoms as possible warning signals of
Parents should report any such symptoms to the pediatrician along with
unexplained fever or frequent infections. Vision problems, weight loss,
lack of appetite, depression, swollen glands, paleness, or general
weakness are other reasons for parents to consult the pediatrician.
Generally, the earlier cancer is diagnosed and treated, the better the
chance of a cure, although not all cancers have early symptoms.
Diagnosis begins with a complete medical history, including family history
of cancer, and a thorough physical examination. The doctor observes and
palpates (applies pressure by touch) different parts of the body in order
to identify any variations from normal size, feel, and texture of an organ
or tissue. The doctor looks inside the mouth for abnormalities in color,
moisture, surface texture, or the presence of any thickening or sores in
the lips, tongue, gums, the roof of the mouth, or the throat. The doctor
observes the front of the neck for swelling and may gently manipulate the
neck and palpate the front and side surfaces of the thyroid gland at the
base of the neck, looking for nodules or tenderness. The doctor also
palpates the lymph nodes in the neck, under the arms, and in the groin,
looking for enlargement. The skin is examined for sores that are slow to
those that bleed, ooze, or crust; irritated patches that may itch or
hurt; and any change in the size of a wart or a mole.
In adolescent females, a pelvic exam may be conducted to detect cancers of
the ovaries, uterus, cervix, and vagina. The doctor first looks for
abnormal discharges or the presence of sores. Then the internal pelvic
organs such as the uterus and ovaries are palpated (touched while applying
gentle pressure) to detect abnormal masses. Breast examination evaluates
unevenness, discoloration, or scaling; both breasts are palpated to feel
for masses or lumps.
In adolescent males, inspection of the rectum and prostate may be included
in the physical examination. The doctor inserts a gloved finger into the
rectum and rotates it slowly to feel for growths, tumors, or other
abnormalities. The testes are examined visually, looking for unevenness,
swelling, or other abnormalities. The testicles are palpated to identify
lumps, thickening or differences in size, weight, or firmness.
If an abnormality is detected on physical examination, or symptoms
suggestive of cancer are noted, diagnostic tests will be performed.
Laboratory studies of sputum, blood, urine, and stool can detect
abnormalities that may confirm cancer. Sputum cytology involves the
microscopic examination of phlegm that is coughed up from the lungs. Tumor
markers, specific proteins released by certain types of cancer cells, can
be detected by performing a test on venous blood. If leukemia or lymphoma
is suspected, a complete blood count (CBC) with peripheral smear
(differential) is done to evaluate the number, appearance, and maturity of
red blood cells (RBCs) and white blood cells (WBCs) and to measure
hemoglobin, hematocrit, and
. A bone marrow biopsy may be done to determine what type of cells is
present in the bone marrow. Blood chemistries will be done to help
determine if liver or kidney problems are present. Blood chemistries are
also useful in monitoring the effectiveness of treatment for all types of
cancer and in following the course of the disease and detecting
Diagnostic imaging techniques such as
magnetic resonance imaging
(MRI), ultrasound, and fiberoptic scope examinations (such as colonoscopy
or sigmoidoscopy) can help determine the location, size, and
characteristics of a tumor even if it is deep within the body.
are often used for initial evaluation, because they are relatively cheap,
painless, and easily accessible. In order to increase the information
obtained from a conventional x ray, air or contrast media (such as barium
or iodine) may be used to enhance the images.
The most definitive diagnostic test for cancer is a biopsy, which is the
surgical removal of a piece of suspect tissue for staining and microscope
examination (cytochemistry). By examining certain cell characteristics,
abnormalities can be identified and the presence of specific types of
cells can be diagnostic for certain cancers. The biopsy provides
information about the type of cancer, its stage, the aggressiveness of the
cancer in invading nearby tissue or organs, and the extent of metastases
at diagnosis. The pathologist who evaluates cancer cells in biopsied
tissue designates the cancer as being stage I, II, III, or IV, in terms of
the degree of metastasis.
Newer molecular and cellular diagnostic testing, such as polymerase chain
reaction (PCR), allows the molecular genetic analysis of tumors.
Cytogenetic analysis of tumor chromosomes, for example, can identify
structural abnormalities that may explain the unique origins of cancer in
an individual child. Spectral karyotyping (SKY), an advanced method of
screening chromosomes for numeric and structural abnormalities, is used to
evaluate pediatric tumors. Gene sequences can also be evaluated in a
method (comparative genomic hybridization) that compares samples from a
tumor and normal tissue after both have been exposed to the same
radioactive material. This method can determine gains and losses in DNA in
the region of the tumor, detecting alterations that have caused the
cancer. The developing science of proteomics studies specific proteins in
cells and may someday be able to provide detailed assessment of cancer
The aim of cancer treatment is to remove or destroy all or as much of the
primary tumor as possible and to prevent its recurrence or metastases.
While devising a treatment plan for cancer, the likelihood of curing the
cancer has to be weighed against the side effects of the treatment. If the
cancer is highly aggressive and cure is not likely, treatment will be
aimed at relieving symptoms and controlling the cancer for as long as
Cancer treatment is always tailored to the individual. The treatment
choice depends on the type and location of cancer, the extent to which it
has already spread, and the age, sex, and general health status of the
individual. The major types of treatment are: surgery, radiation,
, immunotherapy, hormone therapy, and bone-marrow transplantation.
Advances in molecular biology and cancer genetics have contributed greatly
to the development of therapies that provide cell-targeted treatment.
Genetic testing uses molecular probes to identify gene mutations that have
been linked to specific cancers. In the early 2000s ongoing research is
focused on new treatment and prevention methods, including
molecular-targeted therapies, virus therapy, immunotherapy, and drug
therapy that stimulates the self-destruction of cancer cells (apoptosis).
Targeted molecular therapy, although as of 2004 still the subject of
concentrated research, was being used effectively in pediatric study
subjects where it has been shown to reduce the toxicity seen with
conventional chemotherapy. Unlike chemotherapy, which treats all cells
uniformly, targeted molecular therapy can focus on selected cells without
affecting normal cells and tissues. This refinement frees children from
some of the long-term toxic effects and complications that can negatively
affect quality of life and survival even if the cancer is cured.
Surgical removal of a solid tumor is most effective with small tumors
confined to one area of the body. Surgery removes the tumor (tumor
resection) and usually part of the surrounding tissue to ensure that no
cancer cells remain in the area. Since cancer usually spreads via the
lymphatic system, adjoining lymph nodes are sometimes removed as well.
Surgery may also be preventive or prophylactic, removing an abnormal
looking area of tissue that is likely to become malignant over time.
During surgery biopsies may also be performed on tissue that may be
affected by metastases. Surgery is not a typical treatment for leukemia or
lymphoma, which arise in the circulatory system and lymphatic systems that
extend throughout the body. Children with osteosarcoma (bone cancer) and
other solid tumors are candidates for surgery, however.
Surgery may be performed in conjunction with radiation (cytoreductive
surgery) or chemotherapy. The surgeon removes as much of the cancer as
possible and the remaining area is treated with radiotherapy or
chemotherapy or both. In advanced metastatic cancer when cure is unlikely,
palliative surgery aims at reducing symptoms. Debulking surgery, for
example, removes part of a tumor that is pressing on other organs and
causing pain. In tumors that are dependent on hormones, one option is to
remove organs that secrete the hormones.
Radiation kills tumor cells and is used alone when a tumor is in a poor
location for surgery. More often, it is used in conjunction with surgery
and chemotherapy. Radiation can be either external or internal. External
radiation is aimed at the tumor from outside the body. In internal
radiation (brachytherapy), radioactive liquid or
A transmission electron micrograph (TEM) of two spindle cell nuclei
from a human sarcoma. Sarcomas are cancers of the connective tissue
(bone, nerves, smooth muscle).
(Photograph by Dr. Brian Eyden. National Audubon Society
Collection/Photo Researchers, Inc.)
pellets are delivered to the cancerous site via a pill, injection, or
insertion in a sealed container.
Chemotherapy is the administration of drugs that kill cancer cells
(cytotoxic drugs). It destroys hard-to-detect cancer cells that have
spread (metastasized) through the circulation or lymph system.
Chemotherapeutic drugs are given orally or intravenously, either alone or
in conjunction with surgery, radiation, or both. When chemotherapy is used
before surgery or radiation, it is known as primary chemotherapy or
neoadjuvant chemotherapy. Because the cancer cells have not yet been
exposed to anti-cancer drugs, they are especially vulnerable, allowing
neoadjuvant therapy to effectively reduce tumor size. However, the toxic
effects of neoadjuvant chemotherapy may be severe, because normal cells
are also destroyed. Chemotherapy may also make the body less tolerant of
the side effects of other treatments such as radiation therapy. Adjuvant
therapy is the more common type of chemotherapy, used to enhance the
effectiveness of other treatments.
Immunotherapy uses the body's own immune system, specifically a
type of disease-fighting white cell called T-cells, to destroy cancer
cells. Tumor-specific proteins that are part of unique genetic mutations
in pediatric cancer, for example, are believed to be ideal targets for
anti-tumor immune processes. Various immunological agents are as of 2004
still in clinical trials and are not as of that year widely available,
though initial results are promising. Monoclonal antibodies are used to
(Table by GGS Information Services.)
fight cancer cells in much the same way as antibodies that are produced by
the body's own immune system work to fight infection. Other
substances are also being used experimentally. They include substances
such as interferons, interleukins, growth factors, monoclonal antibodies,
and vaccines. Unlike traditional vaccines, cancer vaccines do not prevent
cancer but are designed to treat existing disease. They work by boosting
the immune system and training immunized cells to destroy cancer cells.
Hormone therapy is standard treatment for cancers that are
hormone-dependent and grow faster in the presence of specific hormones,
such as cancer of the prostate, breast, and uterus. Hormone therapy blocks
the production or action of these hormones, slowing growth of the tumor
and extending survival for months or years.
Bone marrow is the tissue within bone cavities that produces blood cells.
Healthy bone marrow tissue constantly replenishes the blood supply and is
essential to life. Sometimes drugs or radiation needed to destroy cancer
cells also destroys bone marrow and only replacement with healthy cells
counteracts this adverse effect. A bone marrow transplant involves
removing marrow from a donor and transplanting blood-forming cells to a
recipient. While not a therapy in itself, bone marrow transplantation may
allow a cancer patient to undergo aggressive therapy.
Many specialists work together to treat cancer patients. The oncologist is
a physician who specializes in cancer care and usually coordinates the
treatment plan, directing chemotherapy, hormone therapy, and any treatment
that does not involve radiation or surgery. The radiation oncologist uses
radiation to treat cancer, while the surgical oncologist performs surgery
to diagnose or treat cancer. Gynecologist-oncologists and
pediatric-oncologists, as their titles suggest, are physicians who treat
women's and children's cancers. Radiologists read the x
rays, ultrasound images, CT scans, and MRI images to help diagnose cancer.
Hematologists specialize in disorders of the blood and bone marrow and are
consulted in the evaluation of leukemia, lymphoma, and bone cancer.
A range of alternative treatments are available to help treat cancer that
can be used in conjunction with, or separate from, surgery, chemotherapy,
and radiation. Alternative treatment of cancer is a complicated arena and
a trained complementary health practitioner should be consulted.
Although the effectiveness of complementary therapies such as acupuncture
in alleviating cancer pain have not as of 2004 been clinically proven,
many cancer patients find it safe and beneficial. Bodywork therapies such
as massage and reflexology ease muscle tension and may alleviate side
effects such as
nausea and vomiting
. Homeopathy and herbal remedies used in Chinese traditional herbal
medicine also have been shown to alleviate some of the side effects of
radiation and chemotherapy and are being recommended by many doctors.
Most cancers show good cure rates if detected and treated at early stages.
The prognosis involves the type of cancer, its degree of invasiveness, and
the extent of metastases at diagnosis. In addition, age, general health
status, and response to treatment are important factors. Cancer deaths in
children have shown consistent declines, decreasing between 1975 and 2000
from 50 in 1 million diagnosed to 25 in 1 million. However, cancer is the
leading cause of death among children and adolescents, responsible for
2,700 deaths each year in the United States.
Prevention of cancer means being aware of causes and risks, which involve
a combination of genetic and environmental factors. Except for family
history, specific genetic causes or an inherited predisposition are
unknown in individuals until revealed in the diagnostic process. Known
environmental causes can be avoided, however. A list of guidelines offered
by nutritionists and epidemiologists from leading U.S. universities to
reduce the risk of cancer includes some that may apply to children and
Certain drugs being used as of 2004 for treatment could also be suitable
for prevention, at least prevention of recurrences. For example, the drug
tamoxifen has been very effective against breast cancer and is in 2004
being used to prevent recurrence in breast cancer survivors. Similarly,
retinoids derived from vitamin A are being tested for their ability to
slow the progression of or to prevent head and neck cancers. Certain
studies suggest that cancer incidence is lower in areas where soil and
foods are rich in the mineral selenium.
—In medical usage, benign is the opposite of malignant. It
describes an abnormal growth that is stable, treatable, and generally
—The surgical removal and microscopic examination of living
tissue for diagnostic purposes or to follow the course of a disease.
Most commonly the term refers to the collection and analysis of tissue
from a suspected tumor to establish malignancy.
—The spongy tissue inside the large bones in the body that is
responsible for making the red blood cells, most white blood cells, and
—A substance that can cause cancer to develop.
—Any treatment of an illness with chemical agents. The term is
usually used to describe the treatment of cancer with drugs that inhibit
cancer growth or destroy cancer cells.
—The layer of cells that covers body surfaces, lines body
cavities, and forms glands.
—Treating cancers by changing the hormone balance of the body,
instead of by using cell-killing drugs.
—A mode of cancer treatment in which the immune system is
stimulated to fight the cancer.
—Cells that have been altered such that they have lost normal
control mechanisms and are capable of local invasion and spread to other
areas of the body. Often used to describe a cancer.
—A secondary tumor resulting from the spread of cancerous cells
from the primary tumor to other parts of the body.
—A cancer treatment that uses high-energy rays or particles to
kill or weaken cancer cells. Radiation may be delivered externally or
internally via surgically implanted pellets. Also called radiotherapy.
—A wound, lesion, or ulcer on the skin.
—A growth of tissue resulting from the uncontrolled proliferation
A diagnosis of childhood cancer raises many uncertainties and concerns for
parents, including how to acquire the most effective therapy. Advances in
molecular and cellular technologies have improved both the diagnosis and
treatment of pediatric cancer and also carry with them the possibility of
someday curing and preventing cancer in children. While cancer was at one
time nearly always fatal in children, as of 2004 more than 75 percent of
children diagnosed with cancer
enjoyed disease-free survival. Targeted molecular therapy and
immunotherapies are the ongoing focus of concentrated research, and
studies using these cell-selective technologies in treating children have
shown encouraging results, both in earlier responses and reduced toxicity
and complications longer term. Parents can be assured of access to the
current knowledge base in molecular biology and advanced treatment
technologies that promise better outcomes.
Janes-Hodder, Honna, et al.
Childhood Cancer: A Parent's Guide to Solid Tumor Cancers
, 2nd ed. Cambridge, MA: O'Reilly Media Inc., 2002.
Woznick, Leigh A., and Carol D. Goodheart.
Living with Childhood Cancer: A Practical Guide to Help Families Cope.
Washington, DC: American Psychological Association (APA), 2002.
American Cancer Society.
1599 Clifton Road, NE, Atlanta, GA 30329. Web site:
Cancer Research Institute (National Headquarters).
681 Fifth Avenue, New York, NY 10022. Web site:
National Cancer Institute.
9000 Rockville Pike, Building 31, room 10A16, Bethesda, MD 20892. Web
National Children's Cancer Society.
1015 Locust Suite 600, St. Louis, MO 63101. Web site:
, 2004. Available online at
(accessed December 8, 2004).