When an adult gets cancer, it’s likely to start in the lungs, breast, colon, prostate or skin.
When a kid gets cancer, it may be in the white blood cells or the nervous system, in the brain or bones, in the lymphatic system, muscles or kidneys.
Below is a short description of each main type of childhood cancer.
Acute lymphoblastic leukemia (ALL) is the most common type of childhood cancer. It is a cancer of the blood and bone marrow. Normally the bone marrow makes stem cells that mature into blood cells over time. In ALL, too many stem cells turn into immature white blood cells (lymphoblasts) that don't mature into the normal blood cells (lymphocytes) that fight infection by attacking germs and other harmful bacteria.
Central nervous system (CNS) tumors are cancers of the brain and brain stem. They are the most common solid tumors of childhood and they have the highest mortality rate of the childhood cancers. Types include medulloblastoma, PNET, germ cell tumors, low-grade and high-grade gliomas, ependymoma, astrocytoma and more.
Ewing sarcoma is a less common form of bone tumor, affecting mostly children ages 5 and older. These tumors form in the cavity of the bone.
Hodgkin lymphoma is a cancer of the lymph nodes. It affects teens most commonly, but also younger children. The lymph system is present throughout the body and helps fight infections. Hodgkin lymphoma can start almost anywhere and then spread to almost any organ or tissue, including the liver, bone marrow and spleen.
Myeloid leukemias are more rare and difficult to cure than the more common Acute Lymphoblastic Leukemia (ALL). In leukemia, the bone marrow produces large numbers of abnormal blood cells, which flood the bloodstream and lymph system and may invade vital organs. The most common cancer of the myeloid cells is acute myeloid leukemia (AML). Others include juvenile myelomonocytic leukemia (JMML), chronic myelogenous leukemia (CML), acute promyelocytic leukemia (APL) and myelodysplastic syndromes (MDS).
Neuroblastoma is a cancer of the sympathetic nervous system, a message network between the brain and other parts of the body. Neuroblastoma tumors can grow in the abdomen, neck or pelvis. It is the most common type of cancer in infants, and can form before birth. The average age of diagnosis is 2, and it is rare in children over 10.
Non-Hodgkin lymphoma (NHL) are cancers of the cells of the immune system (T and B lymphocytes, natural killer cells). Cells of the immune system are produced in the bone marrow and then travel to all the lymph glands, the thymus gland, areas of the intestinal tract, tonsils and spleen, so a lymphoma can develop in any of those sites. The four major subtypes of NHL in children are lymphoblastic, Burkitt, large B cell and anaplastic large cell.
Osteogenic sarcoma (osteosarcoma) is the most frequently diagnosed type of bone tumor, usually found in adolescents and young adults. Tumors are most often in the large bones of the upper arm (humerus) and the leg (femur and tibia).
Retinoblastoma is a cancer of the retinoblasts, or "baby" cells in the retina, responsible for vision. Retinoblastoma occurs most often in children from birth to age 3. About 40% of these children have the genetic form of the disease; with every cell in the retina susceptible to tumor formation, usually both eyes are affected. The other 60% have the non-genetic type, affecting only one eye. Since removal of the eye can cure most children, research is now focused on preserving vision.
Rhabdomyosarcoma is the most common of the soft tissue sarcomas which can be found anywhere in the body. Rhabdomyosarcoma is a tumor that arises in the muscle cells, and is the most common type in children under age 10. The other soft tissue tumors are more rare and tend to be found in adolescents. They include fibrosarcomas, synovial sarcomas, malignantperipheral nerve tumors, leiomyosarcoma, liposarcoma and others even more rare. Some soft tissue tumors are similar to those found in adults, while others are very unique to children.
Wilms tumor accounts for about 90% of kidney tumors in children. About 95% of children with this tumor have a "favorable histology" (better cure rate with less treatment) as determined by the pattern the pathologist sees in the tumor cells. The other 5% have anaplastic Wilms tumor, which is much more resistant to treatment.
Other rare childhood cancers are actually not so rare, when added together, as they account for about 30% of cancers diagnosed in children and adolescents. Because so few children are diagnosed with each type, however, it is very difficult to do research on these cancers. They include clear cell sarcoma of the kidney, rhabdoid tumor of the kidney, germ cell tumors, liver tumors (hepatoblastoma and hepatocellular carcinoma), adrenocortoco carcinoma, colon cancer, melanoma, nasalpharangyal cancer, thyroid tumors and others.