Approximately 1 in 285 children in the United States will be
diagnosed with cancer before the age of 20. While advances in treatment have increased the survival rate for many childhood cancers, the disease is still the second leading cause of death (following accidents) in children ages 5 to 14.
Cancer happens when abnormal cells grow and spread quickly. Unlike normal cells, cancer cells group or lump together to form a tumor. The body's healthy tissue is said to be
benign (i.e. not cancerous). There are some tumors that are considered benign but may still require therapy to aid with symptoms management, etc.
Sometimes cancer cells break away from the original tumor and invade other parts of the body. They can go on to form new tumors. If not treated successfully, these malignant masses will continue to enlarge and possibly spread to other parts of the body. The medical term for this is
metastasis. It is important to keep in mind that cancer is identified according to the original location and cell type.
Example: A colon tumor that metastasizes to the liver is not the same disease as primary liver cancer, nor is it treated the same way. The new malignancy would be referred to as
"colon cancer metastatic to the liver." Its cells, though found in the liver, are colon-cancer cells.
Early detection is crucial to a cancer patient's prognosis, because tumors that remain localized to the original site are generally more easily controlled or cured than tumors that have metastasized.
Causes of Childhood Cancer:
The cause of childhood cancer is largely unknown and the cancers that children get generally are not preventable. A small number of childhood cancers can be related to Down's syndrome, other chromosomal abnormalities, or exposure to radiation.
Types of Childhood Cancers:
Although cancer is the most deadly disease of childhood and adolescence, it strikes nearly 15,500 children a year, as compared to approximately 1.2 million adults. Nine in ten adult cancers are
carcinomas, malignancies that take hold in the cells lining the inner or outer surfaces of organs such as the lung, breast, prostate, colon and bladder. Cancers of children and adolescents belong mainly to four other groups:
leukemias, lymphomas, sarcomas, and gliomas.
What are the most common cancers in children and adolescents?
The most common cancers among children and adolescents vary by age and are shown in the chart below.
Leukemia is cancer of the bone marrow, which produces three types of blood cells. Leukemias are also the most common of childhood cancers. White blood cells (leukocytes) serve as the body's defense system against infection. In leukemia, the marrow produces an overabundance of cancerous white cells. Eventually they crowd out the healthy, infection-fighting mature leukocytes in the marrow and the bloodstream, opening the door to viruses, bacteria and other microorganisms. At the same time, the impaired marrow grinds out fewer oxygen-toting red blood cells and fewer platelets, the clotting cells responsible for stopping bleeding.
Types of leukemia include:
Acute lymphoid leukemia (ALL) - Affects white blood cells called
Acute myeloid leukemia (AML) - Affects other white blood cells called
Because it floods the blood with malignant white cells, the disease is by nature
systemic, or system-wide. When the cancer spreads outside the bone marrow, the blood vessels may whisk it to the brain and spinal cord, the testicles, the ovaries, the kidneys and other organs.
Lymphoma is a cancer of the immune system and lymphoid tissues. They most often grow in lymph nodes and other lymph tissues, like the tonsils or thymus. Lymphomas can also affect the bone marrow and other organs, and can cause different symptoms depending on where the cancer is.
Types of lymphomas include:
Hodgkin disease (or Hodgkin lymphoma) - Usually progresses at a slow but predictable rate and is extremely responsive to treatment. It is seen more often in adolescent and young adults. With a five-year survival rate exceeding 90%, it is one of the most curable cancers of adolescence.
Non-Hodgkin lymphoma - The three major types of childhood non-Hodgkin lymphomas are more aggressive and harder to control, although the overall cure rate is still a promising 75%. Doctors can determine whether a child has
small-cell noncleaved lymphoma (the most common type),
lymphoblastic lymphoma, or
large-cell lymphoma (the least common type) by the appearance of the cells under the microscope and other more sophisticated tests.
Because there is so much lymph tissue in the body, Hodgkin lymphoma and non-Hodgkin lymphoma can occur and spread virtually anywhere. When these cancers metastasize, it's often to the liver, the bone marrow or the spleen.
There are many types of brain tumors, and the treatment and outlook for each is different. Because the brain is a frequent site of metastatic tumors from other parts of the body, doctors look at the tumor's grade rather than its stage to help them determine the most appropriate treatment. The grade, expressed as low or high, describes the cancer cells' appearance and behavior.
Pediatric brain tumors fall into one of four categories. Their names reflect the types of cells in which these tumors arise.
Astrocytomas - Low-grade astrocytomas, which look similar to healthy astrocytes, grow slowly and rarely spread to other parts of the brain, whereas high-grade brain tumors are much more aggressive.
Primitive neuroectodermal tumors – Comes from primitive nerve cells and are rarely seen in adolescents.
Brain-stem gliomas - Develop in the bundle of nerve tissue at the base of the brain, where crucial functions such as heart rate, breathing, and swallowing are regulated.
Ependymomas - Usually arise in the membranous lining of the ventricles, the four interconnected hollow pockets within the brain. The ventricles produce the cerebrospinal fluid that surrounds and cushions the brain and the spinal cord. Consequently, the fluid often sends malignant cells up and down the central nervous system.
Rhabdomyosarcoma is a cancer of muscle tissue. This type of cancer can start nearly any place in the body, including the head and neck, groin, abdomen, pelvis, or in an arm or leg. Children are more commonly diagnosed with the disease still limited to the original site. When rhabdomyosarcoma does spread, it typically creates new lesions in the lymph nodes, bone, bone marrow, or lung.
There are two main types of pediatric rhabdomyosarcoma:
Alveolar rhabdomyosarcoma – Is the rarer form more likely seen in teenagers and involves large muscles of the trunk, arms, and legs.
Embryonal rhabdomyosarcoma - Seen in infants and young children and occurs most commonly in the head and neck, bladder, prostate, testicles, and vagina.
Primary bone cancers (cancers that start in the bones) occur most often in older children and teens, but they can develop at any age. Primary bone cancer is different from metastatic bone cancer, which is cancer that starts somewhere else in the body and then spreads to the bones. Metastatic bone cancer is more common than primary bone cancer, because many types of cancer (including many cancers in adults) can spread to the bones.
Two main types of primary bone cancers occur in children:
Osteosarcoma - It often strikes during the growth spurt of puberty. Boys and girls who sprout up rapidly can possibly be at greater risk of developing the disease than are children whose growth rate is average or less than average, although a growth spurt should not be cause for alarm. About half of osteosarcomas develop in the region of the knee.
Ewing sarcoma – It is a less common type of bone cancer. The most common places for it to start are the pelvic (hip) bones, ribs, shoulder blades, and the long bones in the upper legs and arms.
Both cancers may spread to the lungs, as well as to other bones and soft tissue.
Once cancer is definitively diagnosed, the oncologist orders additional tests to establish the size and extent of the tumor.
Staging, as this is called, is really just a universal language for expressing this information. A commonly used staging system assigns each tumor a number from 0 to 4.
Stage 1 and Stage 2 disease are still confined near the original site.
Stage 3 tells the doctor that the cancer has invaded neighboring sites or has spread to nearby lymph nodes.
Stage 4 is defined by spread to distant lymph nodes or organs.
Not all cancers are staged using numbers; some are simply classified as localized or disseminated.
Cancers of childhood tend to be more
curable than adult tumors. While the five-year survival rate for adults has struggled to exceed the 50% mark, survival rates in pediatrics are now approaching 90%—a dramatic increase from the mid-1970s, when nearly half of all children with cancer died.