Cancer is a group of many related diseases that begin in cells, the body's basic unit of life. To understand cancer, it is helpful to know what happens when normal cells become cancerous.
The body is made up of many types of cells. Normally, cells grow and divide to produce more cells only when the body needs them. This orderly process helps keep the body healthy. Sometimes, however, cells keep dividing when new cells are not needed. These extra cells form a mass of tissue called a growth or tumor.
Tumors can be benign or malignant. Benign tumors are not cancer. They can often be removed and, in most cases, they do not come back. Cells from benign tumors do not spread to other parts of the body. Most important, benign tumors are rarely a threat to life. Malignant tumors are cancer. Cells in these tumors are abnormal and divide without control or order. They can invade and damage nearby tissues and organs. Also, cancer cells can break away from a malignant tumor and enter the bloodstream or the lymphatic system. That is how cancer spreads from the original cancer site to form new tumors in other organs. Cancer that has spread is called metastatic cancer.
Most cancers are named for the organ or type of cell in which they begin. When cancer spreads (metastasizes), cancer cells are often found in nearby or regional lymph nodes (sometimes called lymph glands). If the cancer has reached these nodes, it means that cancer cells may have spread to other organs, such as the liver, bones, or brain. When cancer spreads from its original location to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if lung cancer spreads to the brain, the cancer cells in the brain are actually lung cancer cells. The disease is called metastatic lung cancer (not brain cancer).
Children can get cancer in the same parts of the body as adults do, but some types of cancer are more common in children. The most common form of childhood cancer is leukemia. Leukemia is cancer of the blood. It develops in the bone marrow, which is a spongy substance that fills the inside of the bones and makes blood cells. Other cancers often found in children are brain tumors, childhood lymphomas, Hodgkin's disease, Wilms' tumors, neuroblastomas, osteogenic sarcomas, Ewing's sarcomas, retino-blastomas, rhabdomyosarcomas and hepatoblastomas.
Chondrosarcoma forms in cartilage, the rubbery tissue around the joints. Found mainly in adults, although it can occur in children.
The most common sites for Ewing's sarcoma are the hipbones, long bones in the thigh (femur) and upper arm (humerus), and ribs. Occurs between ages 10 and 25.
Osteosarcoma is the sixth most common malignancy in children and the most common type of bone cancer in children. Usually affects the thigh bone (femur), upper arm bone (humerus), or one of the long bones of the lower leg (tibia). Occurs between ages 10 and 25.
Leukemia is a type of cancer. Cancer is a group of many related diseases. All cancers begin in cells, which make up blood and other tissues. Normally, cells grow and divide to form new cells as the body needs them. When cells grow old, they die, and new cells take their place.
The blood cells are very abnormal. They cannot carry out their normal work. The number of abnormal cells increases rapidly. Acute leukemia worsens quickly.
Acute lymphocytic leukemia accounts for about 3,800 new cases of leukemia each year. It is the most common type of leukemia in young children. It also affects adults.
Acute myeloid leukemia accounts for about 10,600 new cases of leukemia each year. It occurs in both adults and children.
Early in the disease, the abnormal blood cells can still do their work, and people with chronic leukemia may not have any symptoms. Slowly, chronic leukemia gets worse. It causes symptoms as the number of leukemia cells in the blood rises.
Chronic lymphocytic leukemia accounts for about 7,000 new cases of leukemia each year. Most often, people diagnosed with the disease are over age 55. It almost never affects children.
Also called hepatoma, liver cancer is a rare disease. When the tumor is just in the liver and can be removed with surgery, it is highly curable. Two types of cancer can start in the liver and are identified by how they look under the microscope.
Hepatoblastoma can be inherited. Usually occurs before age 3.
Children infected with hepatitis B or C (viral infections of the liver) are more likely to get this type of cancer. Occurs most often in children age 4 or younger and those between ages 12 and 15.
These sarcomas start in soft tissues, which connect, support, and surround body parts and organs.
Rhabdomyosarcoma is the most common type of soft tissue sarcoma. It starts in muscle tissue and can occur anywhere in body. It is most often found in the head and neck, kidneys, bladder, arms, legs, and trunk. Affects children ages 2 to 6 years old.
Lymphoma is a tumor of the lymph tissue. Because lymph tissue is in many parts of the body, lymphomas can start almost anywhere.
A type of non-Hodgkin's lymphoma. In Americans, the usual site is the abdomen. Age range is 2-16 years.
Hodgkin's disease is a cancer that tends to affect the lymph nodes that are close to the body's surface, such as those in the neck, armpit, or groin area. Occurs mainly in young adults and in people over age 65 but can affect teenagers and children. Lymphomas are the third most common childhood cancer. Rare under age 5.
In children, non-Hodgkin's lymphoma affects lymph nodes that are found deeper in the body. The bowel is the most frequent spot, often in the area next to the appendix, or in the upper part of the chest. Occurs most often in ages 10 to 20 an is unusual under age 3.
Brain cancer is the most common solid tumor cancer in childhood. The most common brain tumors are called gliomas; there are several types of gliomas. Occurs most often in children from birth to 15 years old.
Cancer of certain nerve cells of the body is called neuroblastoma. The second most common solid tumor cancer in children, it usually starts in abdomen, either in the adrenal glands (located just above kidneys in back of the upper abdomen) or around the spine. It can also start around the spinal cord in the chest, neck, or pelvis. Occurs most often in babies and very young children.
Retinoblastoma is cancer of the eye. It affects the retina, a thin membrane in the back of eye that works like a camera, making a picture of what we see. Some children have retinoblastoma that runs in families. It usually occurs in only one eye, but sometimes affects both eyes. Occurs mostly in children younger than 5 years old.
This type of cancer starts in the kidney. It is the most common type of kidney cancer in children but is very different from kidney cancer in adults. May be hereditary. Age range 6 months to 10 years - greatest in first 5 years.
Power lines and childhood cancers: Children living near overhead power lines may have an increased risk of leukemia but the association may not be causal, UK researchers say.
Links to Internet Resources on Childhood Cancers: This page lists the best (IMHO) sites for childhood cancer and for cancer in general. They are sort of arranged from favorite to less-informative, but each is worth a visit.