Cancer is a group of diseases in which the genetic controls that regulate the normal proliferation of the body’s cells become disabled, and the cells begin to divide chaotically, at an accelerated pace. In time, they amass into a lump of excess tissue called a tumor. A tumor that does not invade normal tissue is said to be benign. It is not cancerous. Aside from tumors embedded in the brain, most benign growths can be removed surgically without incident.
Invasive tumors are cancerous. If not treated successfully, these malignant masses will continue to enlarge and possibly spread to other parts of the body. The tumor can extend through one organ and into another, or a colony of cells from the primary tumor may break off and travel the circulatory system to seed a secondary tumor a distance away. 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. A colon tumor that metastasizes to the liver is not the same disease as primary liver cancer, nor is it treated the same way. In this example, 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.
What is Staging?
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. Generally, stage 1 and stage 2 disease are still confined near the original site, while 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.
Types of Childhood Cancers
Although cancer is the most deadly disease of childhood and adolescence, it strikes just nine thousand youngsters 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.
|Neuroblastoma (a cancer of the nervous system)*
|Wilms’ tumor (a cancer of the kidney)*
|Osteosarcoma (bone cancer)
|Ewing’s sarcoma (bone cancer)
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 percent mark, about 70 percent of young patients—nearly three in four—can expect to enjoy a normal life span. That is a dramatic increase from the mid-1970s, when nearly half of all youngsters with cancer died.
This is cancer of the bone marrow, which manufactures the three types of blood cells. 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.
Leukemias are classified as acute or chronic. Young leukemia patients usually develop the acute forms. Acute lymphocytic leukemia (ALL) affects white blood cells called lymphocytes, while acute myelogenous leukemia (AML) affects other white blood cells called granulocytes and monocytes. You may hear leukemia referred to as a “liquid” tumor. Because it floods the circulation 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.
Hodgkin’s Disease and Non-Hodgkin’s Lymphoma
These are cancers of the lymphatic system. Intertwined among the blood vessels is a network of thin lymphatic vessels, which collect straw-colored lymph fluid from the body’s tissues and return it to a pair of veins in the upper chest so that it can repeat its excursion through the body as the liquid portion of the blood.
En route, lymph passes through pea-sized organs called lymph nodes, which filter out and destroy infectious agents and toxic substances. The nodes are scattered through the lymphatic system but can be found in large clusters in the neck, pelvis, abdomen, chest and armpits.
Because there is so much lymph tissue in the body, Hodgkin’s lymphoma and non-Hodgkin’s lymphoma can occur and spread virtually anywhere. When these cancers metastasize, it’s often to the liver, the bone marrow or the spleen. Hodgkin’s disease usually progresses at a slow but predictable rate and is extremely responsive to treatment. With a five-year survival rate exceeding 90 percent, it is one of the most curable cancers of adolescence.
The three major types of childhood non-Hodgkin’s lymphomas are more aggressive and harder to control, although the overall cure rate is still a promising 75 percent. Doctors can determine whether a youngster 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. Combined, lymphomas and leukemias account for almost half of all pediatric cancers.
Pediatric brain tumors fall into one of four categories: astrocytomas, primitive neuroectodermal tumors (PNET, for short), brain-stem gliomas, and ependymomas. Their names reflect the types of cells in which these tumors arise.
The brain is a frequent site of metastatic tumors from other parts of the body; primary brain lesions, however, rarely spread beyond the central nervous system. Therefore, 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, rates the cancer cells’ appearance. Do they resemble normal cells? Or do they have the disorganized structure of malignant cells? Grade provides a profile of the cancer’s behavior. 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, which include medulloblastomas, spring 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 disseminates malignant cells up and down the central nervous system.
This is a cancer of muscle tissue. There are two main types of pediatric rhabdomyosarcoma: the rarer form, alveolar rhabdomyosarcoma, which involves large muscles of the trunk, arms and legs is more likely to occur in teenagers; embryonal rhabdomyosarcoma, seen in infants and young children, occurs in the head and neck, bladder, prostate, testicles and vagina. Most youngsters are 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.
Osteosarcoma and Ewing’s Sarcoma
These are cancers of the bone. Osteosarcoma, the more common of the two, 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 youngsters 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, whereas Ewing’s sarcomas frequently target the pelvis, ribs 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. Ewing’s sarcoma sometimes spreads to the bone marrow, the body’s production center for blood cells, thus giving rise to abnormal blood counts.