Leukemia is the most common type of cancer kids get, but it is still very rare. Leukemia involves the blood and blood-forming organs, such as the bone marrow. Bone marrow is the innermost part of some bones where blood cells are first made. A kid with leukemia produces lots of abnormal white blood cells in the bone marrow.
Usually, white blood cells fight infection, but the white blood cells in a person with leukemia don’t work the way they’re supposed to. Instead of protecting the person, these abnormal white blood cells multiply out of control. They fill up the bone marrow and make it hard for enough normal, infection-fighting white blood cells to form.
Other blood cells – such as red blood cells (which carry oxygen in the blood to the body’s tissues) and platelets (which allow blood to clot) – also get crowded out by the white blood cells of leukemia. These cancer cells may move to other parts of the body, including the bloodstream, liver, spleen, and lymph nodes. In those areas, cancer cells can continue to multiply and build up.
Brain and other nervous system cancers are the second most common cancers in children, making up about 22% of childhood cancers. Most brain cancers of children involve the cerebellum or brain stem. In early stages they can cause headaches, nausea, vomiting, blurred or double vision, dizziness, and trouble walking or handling objects. Adults are more likely to develop cancers in different parts of the brain–usually the cerebral hemispheres. Spinal cord tumors are less common than brain tumors in both children and adults.
Non-Hodgkin lymphoma and Hodgkin lymphoma, (sometimes called Hodgkin disease, Hodgkin’s disease, or Hodgkin’s lymphoma), are cancers that start in lymph nodes. These cancers may spread to bone marrow and other organs. They also can cause fever, weakness, and swelling of lymph nodes (“glands”) in the neck, armpit, or groin. Hodgkin lymphoma can occur in both children and adults, and accounts for about 4% of childhood cancers. It is more common, though, in 2 age groups: early adulthood (age 15 to 40, usually 25 to 30) and late adulthood (after age 55). Hodgkin lymphoma is rare before 5 years of age. About 10% to 15% of cases are diagnosed in children 16 years of age and younger.
Bone Cancers: The incidence of primary bone cancer (cancers that started in the bones) is highest in children and adolescents.
Primary bone cancer is different from metastasis bone cancer, which is cancer that has spread to the bone. Metastatic bone cancer is more common than primary bone cancer because many types of cancer can spread to the bone. There are 2 types of primary bone cancers that happen in children:
a) Osteosarcoma is uncommon, comprising a little over 2% of all new childhood cancer cases in the United States. It often causes no pain or symptoms until swelling starts.
b) Ewing sarcoma is a less common primary bone cancer that occurs mostly in children and adolescents. It accounts for a little more than 1% of childhood cancers.
Neuroblastoma is the most common form of cancer that affects children outside of the brain, and which occurs in the first year of life. It can develop anywhere in the body, but most of the time in the abdomen area. It represents almost 7% of cancer in children.
Wilms tumor affects either or both kidneys in children, commonly between the ages of 2 and 3. it can be recognised by swelling or lump in the belly area. Approximately denotes for 6% of childhood cancer.
Rhabdomyosarcoma is a form of cancer where there is unusual soft tissue growth in children. The tumour stems from the cells that develop into voluntary muscles. It can occur in the head and neck, groin, chest, arms and legs. The common symptoms are pain and swelling.
Retinoblastoma is a cancer of the eye. Although relatively rare, it accounts for less than 3% of childhood cancers and about 5% of childhood blindness. It usually occurs in children under the age of 4.
References:
http://www.cancer.org/docroot/CRI/content/CRI_2_4_1X_What_are_the_types_of_childhood_cancers_7.asp
http://kidshealth.org/kid/health_problems/cancer/cancer_kinds.html