TYPES OF CHILDHOOD CANCER
Pediatric Brain Tumors
Brain and spinal cord tumors — known as central nervous system tumors (CNS) — are the most common type of solid tumor in children, constituting about 20 percent of all malignancies in patients under the age of 15. Brain tumors can be either benign (non-cancerous) or malignant (cancerous). There are many different types of brain tumors. Tumors that form in the tissues and cells of a child’s brain are called primary brain tumors. In some cases, tumors that have originated in other parts of the body spread, or metastasize, to the brain.
Astrocytomas are tumors that arise from brain cells called astrocytes. Gliomas originate from glial cells, most often astrocytes.
Astrocytomas are of two main types—high-grade and low-grade. High-grade tumors grow rapidly and can easily spread through the brain. Low-grade astrocytomas are usually localized and grow slowly over a long period of time. High-grade tumors are much more aggressive and require very intensive therapy. The majority of astrocytic tumors in children are low-grade, whereas the majority in adults are high-grade. These tumors can occur anywhere in the brain and spinal cord.
Common sites in children are the cerebellum (the area just above the back of the neck), cerebral hemispheres (the top part of the brain), and the thalamus or hypothalamus (located in the center of the brain).
Some of the more common low-grade astrocytomas are:
Juvenile Pilocytic Astrocytoma (JPA)
Pleomorphic Xantroastrocytoma (PXA)
Desembryoplastic Neuroepithelial Tumor (DNET)
The two most common high-grade astrocytomas are:
Anaplastic Astrocytoma (AA)
Glioblastoma Multiforme (GBM)
Ependymomas arise from cells lining the passageways in the brain that produce and store the cerebrospinal fluid or CSF. (CSF is a fluid that bathes the brain and spinal cord.) These tumors are classified as either supratentorial (in the top part of the head) or infratentorial (in the back of the head). In children, the majority of ependymomas occur as infratentorial tumors arising in or around the fluid-filled fourth ventricle.
3. Medulloblastomas and PNETs
Medulloblastomas are tumors that arise in the posterior fossa region of the brain. The exact cell of origin is not known. These tumors are also referred to as primitive neuroectodermal tumor (PNET). Tumors that have the same characteristics can also arise in other parts of the brain. Representing approximately 15 percent of childhood brain tumors, medulloblastomas are tumors that arise from undeveloped stem cells in the portion of the brain that controls voluntary movement, the cerebellum. They are highly malignant, but with appropriate treatment many children can be cured.
4. Germ Cell Tumors
These tumors arise from various types of “germ cells” found in the brain. Different types of germ cells give rise to different types of tumors, including germinoma, embryonal carcinoma, endodermal sinus tumor and teratoma. These tumors arise primarily in two locations in the center of the brain, the suprasellar and pineal regions. Germ cell tumors commonly malignant.
Leukemias are cancers that occur in the tissues within the body that produce the body’s blood cells and bone marrow. Leukemias are the most common form of childhood cancer. About one-third of all cancers in children under the age of 15 are leukemias, as are about one-fourth of all cancers in people under 20.
Stems cells are present in healthy bone marrow and naturally develop into red blood cells, white blood cells, and platelets — all of which are found in blood. Sometimes certain types of immature white blood cells undergo a random mutation, or change, of a gene in the DNA that can cause the cell to grow and multiply uncontrollably, resulting in leukemia. These uncontrolled cells flood the body’s organs and interfere with their function. The cells also inhibit the body’s ability to produce red and white blood cells and platelets normally.
Stem cells that produce white blood cells come in two major types: myeloid cells and lymphoid cells. When uncontrolled cell growth begins within a descendant of a lymphoid cell, it is acute lymphoblastic leukemia (ALL). This is the most common type of childhood leukemia; it accounts for about 85 percent of all childhood leukemias. When the uncontrolled growth originates within a descendant of a myeloid cell, it is acute myelogenous leukemia (AML), the second most common type of childhood leukemia.
Lymphomas are cancers that develop in the lymphatic system of the body. The lymphatic system is a network of glands and vessels that transports lymph, a clear fluid carrying infection-fighting white blood cells called lymphocytes. Formed from a precursor type of cell called a stem cell, lymphocytes are made and stored in the lymph nodes — small bean-shaped organs found in the neck, chest, abdomen, groin, and in the underarm region. The spleen, thymus, tonsils, and bone marrow are also parts of the lymphatic system. Lymphomas develop when the white blood cells within the lymphatic system begin to grow abnormally.
Lymphomas are the third most common form of cancer among children, following leukemia and brain tumors. There are two general types of lymphoma found in children, Hodgkin Lymphoma and non-Hodgkin’s lymphoma.
According to the National Cancer Institute (NCI) and its most recent Surveillance, Epidemiology, and End Results (SEER) analysis, approximately 1,700 young people under 20 years of age are diagnosed with lymphoma each year in the United States. (Approximately 850-900 diagnosed with Hodgkin Lymphoma and 750-800 with non-Hodgkin’s lymphoma).
Over the last two decades, the incidence of Hodgkin Lymphoma among young people younger than 20 years of age decreased slightly, as reported in the most recent SEER analysis. In the same period of time, the incidence of non-Hodgkin’s lymphoma in children younger than 15 years of age remained fairly constant; while there was a slight increase in the incidence of non-Hodgkin’s lymphoma among 15- to 19-year-olds.
Retinoblastoma, the most common type of eye tumor seen in children, occurs most often in young children before the age of five and affects boys and girls in equal numbers. The tumor may be in one eye (referred to as unilateral retinoblastoma), or in both eyes (bilateral retinoblastoma).
Retinoblastoma tumors originate in the retina, the light-sensitive layer of the eye which enables the eye to see. About 75 percent of retinoblastoma cases are unilateral, and 90 percent of retinoblastoma patients have no family history of the disease.
Retinoblastoma occurs most often before the age of five. There are approximately 350 new diagnosed cases per year in the United States, making it the seventh most common pediatric cancer. Retinoblastoma affects one in every 15,000 to 30,000 live babies born in the United States and is found in boys and girls from all backgrounds.
More than 95 percent of children treated for retinoblastoma in the US are cured. In addition, more than 90 percent of patients retain at least one eye and more than 80 percent of children treated keep 20/20 vision.
Pediatric Sarcomas are cancers that can arise anywhere within the body where there is bone, muscle, or connective tissue. They account for about 10 to 15 percent of all newly diagnosed cancers in children and young adults under the age of 20 in the United States.
Although rhabdomyosarcoma (a tumor arising from muscle), Ewing’s sarcoma (a tumor that typically arises from the bone), and osteosarcoma (a tumor that arises from bone) comprise the majority of sarcomas seen in children and young adults, other more rare forms of sarcomas can also be seen. Patients with certain genetic syndromes such as Li-Fraumeni syndrome are predisposed to developing sarcomas. However, in the vast majority of our patients, there are no predisposing factors.
Wilm’s Tumor is also called nephroblastoma, is the most common type of kidney cancer found in children, accounting for approximately 95 percent of all childhood kidney cancers and six percent of all childhood cancers. About 500 cases are diagnosed in the United States each year, the majority of which are curable.
Named for Max Wilms (1867-1918), the surgeon who first identified the disease in 1899, Wilm’s tumor is a disease in which cancerous cells grow in one or both of the kidneys — two bean-shaped organs located on either side of the spine in the abdominal region. Wilm’s tumor usually occurs in only one kidney (unilateral tumors) when certain cells in that kidney multiply uncontrollably, growing into a malignant, or cancerous, mass. In a small number of cases, Wilm’s tumor can form in both kidneys (bilateral tumors); these do not always occur at the same time — a tumor can be detected in one kidney after first developing in the other.