CHILDHOOD CANCER AWARENESS - CANCER TYPES DEFINED

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TYPES OF CHILDHOOD CANCER

This lens is devoted to finding information on each type of Childhood Cancer! For me, it's learning - so I can share the facts with all of you! Let's all work together to find a CURE FOR CHILDHOOD CANCER!

MANY THANKS TO THE AMERICAN CANCER SOCIETY FOR ALL THE DETAILED INFORMATION REGARDING THE TYPES OF CHILDHOOD CANCER FROM YOUR WEBSITE:
http://www.cancer.org/docroot/home/index.asp?level=0

Thanks so much for stopping by!
Much Love,
Bill & Stacey Reich

OUR PRAYER LIST KIDS

LOVE, THOUGHTS, PRAYERS, & BIG (((HUGS)) ARE WITH YOU ALL!!!

This lens is devoted to finding information on each type of Childhood Cancer! For me, it's learning - so I can share the facts with all of you! Let's all work together to find a CURE FOR CHILDHOOD CANCER!

We have sooo many PRECIOUS children on our Prayer List that are busy kicking cancers butt right now! Please lift them up in your prayers every day! There names are:

ETHAN: www.caringbridge.org/visit/super_ethan

HUNTER: www.caringbridge.org/ma/hunter/

MATTHEW: www.caringbridge.org/canada/matthew/

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YOU SEE ON THIS LENS!

WHAT IS CANCER?

FROM THE AMERICAN CANCER SOCIETY

AMERICAN CANCER SOCIETY: Detailed Guide:
What Is Cancer?

Cancer develops when cells in a part of the body begin to grow out of control. Although there are many kinds of cancer, they all start because of out-of-control growth of abnormal cells.

Normal body cells grow, divide, and die in an orderly fashion. During the early years of a person's life, normal cells divide more rapidly until the person becomes an adult. After that, cells in most parts of the body divide only to replace worn-out or dying cells and to repair injuries.

Because cancer cells continue to grow and divide, they are different from normal cells. Instead of dying, they outlive normal cells and continue to form new abnormal cells.

Cancer cells often travel to other parts of the body where they begin to grow and replace normal tissue. This process, called metastasis, occurs as the cancer cells get into the bloodstream or lymph vessels of our body. When cells from a cancer like breast cancer spread to another organ like the liver, the cancer is still called breast cancer, not liver cancer.

Cancer cells develop because of damage to DNA. This substance is in every cell and directs all its activities. Most of the time when DNA becomes damaged the body is able to repair it. In cancer cells, the damaged DNA is not repaired. People can inherit damaged DNA, which accounts for inherited cancers. Many times though, a person's DNA becomes damaged by exposure to something in the environment, like smoking.

Cancer usually forms as a tumor. Some cancers, like leukemia, do not form tumors. Instead, these cancer cells involve the blood and blood-forming organs, and circulate through other tissues where they grow.

Remember that not all tumors are cancerous. Benign (non-cancerous) tumors do not spread to other parts of the body (metastasize) and, with very rare exceptions, are not life-threatening.

Different types of cancer can behave very differently. For example, lung cancer and breast cancer are very different diseases. They grow at different rates and respond to different treatments. That is why people with cancer need treatment that is aimed at their particular kind cancer.

Cancer is the second leading cause of death in the United States. It is the second leading cause of death after accidents in children from ages 1-14. Half of all men and one third of all women in the United States will develop cancer during their lifetimes. Today, millions of people are living with cancer or have had cancer. The risk of developing most types of adult cancers can be reduced by changes in a person's lifestyle, for example, by quitting smoking, reducing sun exposure, and eating a healthier diet. These risks do not apply to children. Generally, the sooner a cancer is found and treatment begins, the better are the chances for living for many years.

WHAT ARE THE DIFFERENCES
BETWEEN CANCER IN ADULTS
AND CANCER IN CHILDREN?

WHAT ARE THE DIFFERENCES BETWEEN CANCER IN ADULTS AND CHILDREN?

FROM THE AMERICAN CANCER SOCIETY

AMERICAN CANCER SOCIETY: Detailed Guide: Leukemia - Children's
What Are the Differences Between Cancer in Adults and Children?

The types of cancers that develop in children are different from the types that develop in adults. Although there are exceptions, childhood cancers tend to respond better to chemotherapy. Children also tolerate chemotherapy better than adults. But, because chemotherapy can have some long-term side effects, children who survive their cancer need careful attention for the rest of their lives.

Since the 1960s, most children and adolescents with cancer have been treated at specialized centers designed for them. Being treated in specialized centers offers them the advantage of a team of specialists who know the differences between adult and childhood cancers, as well as the unique needs of children with cancers. This team usually includes pediatric oncologists, pathologists, surgeons, radiation oncologists, pediatric oncology nurses, and nurse practitioners.

These centers also have psychologists, social workers, child life specialists, nutritionists, rehabilitation and physical therapists, and educators who can support and educate the entire family.

Most children with cancer in the United States are treated at a center that is a member of the Children's Oncology Group (COG). All of these centers are associated with a university or children's hospital. As we have learned more about treating childhood cancer, it has become even more important that treatment be given by experienced experts.

Revised: 03/06/2006

WHAT ARE BRAIN AND SPINAL
CORD TUMORS IN CHILDREN?

WHAT ARE BRAIN AND SPINAL CORD TUMORS IN CHILDREN?

BRAIN & SPINAL CORD TUMORS IN CHILDREN DEFINED

AMERICAN CANCER SOCIETY: Detailed Guide: Brain / CNS Tumors in Children
What Are Brain and Spinal Cord Tumors in Children?

Brain tumors are masses of abnormal cells that have grown out-of-control. In most other parts of the body, it is critically important to distinguish benign (noncancerous) tumors from malignant (cancerous) ones. Benign tumors are almost never life threatening. The main reason cancers are so dangerous is because they can spread throughout the body. Most brain cancers can spread through the brain tissue but rarely spread to other areas of the body. Even so-called Â"benignÂ" tumors are can, as they grow, compress brain tissue, causing damage that is often disabling and sometimes fatal. For this reason, doctors usually speak of "brain tumors" rather than "brain cancers." The major distinction is how readily they spread through the rest of the brain central nervous system and whether they can be removed and not come back.

The central nervous system is the medical name for the brain and spinal cord. Central nervous system tumors of adults and children often form in different areas, develop from different cell types, and may have a different outlook and treatment. This document refers to children's tumors.

The brain is the center of thought, feeling, memory, speech, vision, hearing, movement, and much more. The spinal cord and special nerves in the head called cranial nerves carry messages between the brain and the rest of the body. These messages tell our muscles how to move, transmit information gathered by our senses, and help coordinate our internal organs. The brain is located within and protected by the skull. Likewise, the spinal cord is protected by the bones of the spinal column. The brain and spinal cord are surrounded and cushioned by a special fluid, called cerebrospinal fluid. Cerebrospinal fluid is produced by the choroid plexus, which is located in cavities within the brain called ventricles. The ventricles as well as the spaces around the brain and spinal cord are filled with cerebrospinal fluid.

Parts of the Brain and Spinal Cord

The brain and spinal cord are the 2 main parts of the central nervous system.

The main areas of the brain include the cerebral hemispheres, cerebellum, and brain stem. Each of these parts has a special purpose. Tumors of different parts of the central nervous system disrupt different functions and cause different symptoms. Any disease involving that particular location within the brain can cause these symptoms, and they do not necessarily mean a brain tumor is present. Also, tumors in different areas of the central nervous system may be treated differently and have a different prognosis (outlook for survival). In very young children, less than 3 years of age, itÂ's often hard to tell which part of the brain is affected during its early development. Very young children may not have the usual symptomns coming from that part of the brain involved as would be seen in adults. In this age group the only symptoms may be nonspecific and include irritability, crying, poor feeding, or vomiting.

The 2 cerebral hemispheres control reasoning, thought, emotion, and language. They are also responsible for your planned muscle movements (throwing a ball, walking, chewing, etc.) and for taking in sensory information such as vision, hearing, smell, touch, and pain.

The symptoms caused by a tumor in a cerebral hemisphere depend on the part of the hemisphere in which the tumor arises. Common symptoms include:

seizures
trouble speaking
a change of mood such as depression
a change in personality
numbness, weakness or paralysis of part of the body
changes in vision, hearing, and sensation
The cerebellum controls coordination of movement. Tumors of the cerebellum cause difficulty with coordination in walking, difficulty with fine movements of arms and legs, and changes in rhythm of speech.

The brain stem contains bundles of very long nerve fibers (axons) that carry signals controlling muscles and sensation or feeling from the cerebrum to and from the rest the body. In addition, most cranial nerves (which carry signals to and from the face, eyes, tongue, and mouth) start in the brain stem. Special centers in the brain stem also control breathing and the beating of the heart.

Tumors in this critical area of the brain may cause weakness, stiff muscles, or problems with sensation, hearing, facial movement, and swallowing. Double vision is a common early symptom of brain stem tumors, as are problems with coordination in walking. Because tumors of the brain stem often intermingle with normal nerve cells and the brain stem is so essential for life, it may not be possible to surgically remove these tumors from the brain stem.

The spinal cord, like the brain stem, contains bundles of very long axons (wire-like extensions) that carry signals controlling muscles, sensation or feeling, and bladder and bowel control. Spinal cord tumors may cause weakness, paralysis, or numbness. Because the spinal cord is such a narrow structure, tumors arising within it usually cause symptoms involving both sides of the body (for example, weakness or numbness of both legs). This is different than tumors of the brain, which usually affect only one side of the body. Moreover, most tumors of the spinal cord arise below the neck after nerves to the arms have branched off the spinal cord, so that only lower body functions - bowel, bladder, or leg - are affected.

Tumors may also arise from cranial nerves. The most common cranial nerve tumor in children is optic glioma, a tumor of the optic nerve (the optic nerve is actually an extension of brain tissue to the eye) causing blindness. Tumors arising from other cranial nerves may cause hearing loss (acoustic nerve) in one or both ears, facial paralysis (facial nerve), or facial numbness or pain (trigeminal nerve). Tumors arising in the nerves of the peripheral nervous system (parts of the nervous system other than the brain and spinal cord) generally cause pain, weakness,and/or loss of sensation in the area served by that nerve. They can also weaken the muscles controlled by that nerve.

Types of Cells and Tissues in the Brain and Spinal Cord

The brain consists of different kinds of tissues and cells. Different types of tumors can start in these different cell and tissue types. These different types of tumors have varying outlooks for survival and may be treated differently.

Neurons: These are the most important cells within the brain. They send signals through the axons. Axons may be very short (in the brain) or 2 to 3 feet long (in the spinal cord). Electric signals carried by neurons determine thought, memory, emotion, speech, muscle movement, and just about everything else that the brain and spinal cord do. Unlike many other types of cells that can grow and divide to repair damage from injury or disease, neurons quit dividing about 1 year after birth (with a few exceptions). Neurons do not usually form tumors, but they are damaged by tumors that start nearby.

Glial cells: Most brain and spinal cord tumors develop from glial cells. There are 3 types of glial cells - astrocytes, oligodendrocytes, and ependymal cells. Tumors of glial cells are sometimes referred to as a group and called gliomas. A fourth cell type called microglia is part of the immune system and is not truly glial in origin. Normal glial cells grow and divide very slowly. Glial cells are the supporting cells of the brain and continue to increase in number until the child is 5 years of age. At this time, the brain reaches its maximum size and will be the same size throughout oneÂ's lifetime.

Astrocytes help support and nourish neurons. When the brain is injured, astrocytes form scar tissue that helps repair the damage.

Oligodendrocytes make myelin, a substance that surrounds and insulates axons of the brain and spinal cord. This allows oligodendrocytes to help neurons transmit electric signals through axons.

Ependymal cells line the ventricles within the central part of the brain and form part of the pathway through which cerebrospinal fluid travels.

Microglia represent 10% to 20% of the total population of glial cells in the brain. They are the immune (infection fighting) cells of the central nervous system.
Neuroectodermal cells: These are primitive cells that are probably the remains of embryonic cells and are found throughout the brain. The most common tumor that comes from these cells is the medulloblastoma, which arises in the cerebellum.

Meninges: These are specialized tissues that line the cerebrospinal fluid-filled spaces surrounding the brain and spinal cord. The meninges help form the spaces through which cerebrospinal fluid travels.

Choroid plexus: The choroids plexus is the area of the brain within the ventricles that makes cerebrospinal fluid, which nourishes and protects the brain.

Pituitary gland and hypothalamus: The pituitary is a gland found at the base of the brain. The hypothalamus is a part of the brain next to the pituitary gland. Both of these tissues help regulate the activity of several other glands. For example, they control the production of thyroid hormone by the thyroid gland, the production and release of milk by the breasts, and the production of male or female hormones by the testicles or ovaries. They also produce growth hormone, which stimulates body growth, and vasopressin, which regulates water balance by the kidneys.

The growth of tumors in or near the pituitary or hypothalamus, as well as surgery and/or radiation therapy in this area, can interfere with these functions. Consequently, a child may have low levels of one or more hormones and may need hormone treatments to correct any hormone deficiency.

Pineal gland: The pineal gland is not strictly part of the brain. It is, in fact, an endocrine gland that sits between the cerebral hemispheres. Its function is probably to make melatonin, a hormone that responds to changes in light.

Blood-brain barrier: Unlike most other organs, there is a barrier between the blood and the tissues of the central nervous system (brain and spinal cord) that keeps many drugs from getting into the brain, including most chemotherapy drugs that are used to kill cancer cells. However, some chemotherapy drugs can cross the blood-brain barrier to treat some malignant brain tumors.

Types of Brain and Spinal Cord Tumors

Sometimes brain tumors are found not to have started in the brain but rather to have spread, or metastasized, from some other part of the body. Tumors that start in other organs and then spread to the brain are called metastatic brain tumors and those that start in the brain are called primary brain tumors. This is important because metastatic and primary brain tumors are usually treated differently.

In children, metastatic tumors to the brain are much less common than primary brain tumors. Unlike other cancerous tumors, tumors arising within the brain or spinal cord rarely metastasize to distant organs. They cause damage because they spread locally and destroy normal tissue where they arise. This document only covers primary brain tumors.

Gliomas: This is not a specific type of cancer. Glioma is a general category that includes glioblastoma multiforme, primitive neuroectodermal tumors, anaplastic astrocytoma, astrocytomas, oligodendrogliomas, ependymomas, brain stem gliomas and optic gliomas. Because this word is often used in discussing brain tumors, it is defined here in an attempt to reduce confusion with it.

Tumors can form in any type of tissue or cell within the brain or spinal cord. Some tumors contain a mixture of cell types. The most common brain and spinal cord tumors of children are astrocytomas. The second most common are primitive neuroectodermal tumors (23%), and the third most common are other kinds of gliomas such as brain stem gliomas (15%). Ependymomas are the fourth most common at 9%. All the others are fairly uncommon and account for only 3%.

Astrocytoma: Most tumors that arise within the brain itself start in brain cells called astrocytes, a kind of glial cell. These tumors are called astrocytomas. About half of all childhood brain tumors are astrocytomas. Many astrocytomas cannot be cured because they spread widely throughout, and intermingle with, the normal brain tissue. They are called infiltrating astrocytomas. Sometimes infiltrating astrocytomas spread along the cerebrospinal fluid pathways. But it is very rare for them to spread outside of the brain or spinal cord.

Infiltrating astrocytomas are classified as low grade, intermediate grade, or high grade. A pathologist (a doctor specializing in the diagnosis of diseases by laboratory tests) will grade them based on how the cells from a biopsy specimen (sample of the tumor) look under the microscope. Low-grade astrocytomas are the slowest growing and the most common type of astrocytoma in children. Intermediate-grade astrocytomas, or anaplastic astrocytomas, grow at a moderate rate. The highest-grade astrocytomas, glioblastomas, are the fastest growing.

There are some special types of astrocytomas that tend to have a particularly good prognosis. These are juvenile pilocytic astrocytomas and subependymal giant cell astrocytomas.

Juvenile pilocytic astrocytomas most commonly occur in the cerebellum but also occur in the optic nerve, hypothalamus, brain, or other areas.

Subependymal giant cell astrocytomas occur in the ventricles and are almost always associated with tuberous sclerosis (an inherited condition which may also cause epilepsy, mental retardation, and tumors of the skin and kidneys).
Certain tumors possibly of mixed glial and neuronal origin that occur in children and young adults and rarely in older adults also have a good prognosis. One such tumor is the pleomorphic xanthoastrocytoma and another is the dysembryoplastic neuroepithelial tumor. Although they appear malignant under the microscope, these tumors are relatively benign and most are cured by surgery alone.

Oligodendrogliomas: These tumors start in brain glial cells called oligodendrocytes. They spread or infiltrate in a manner similar to astrocytomas and, in most cases, cannot be completely removed by surgery. A small number of oligodendrogliomas, however, are associated with long-term survival of 30 or 40 years. Oligodendrogliomas may spread along the cerebrospinal fluid pathways but rarely spread outside the brain or spinal cord.

Optic Glioma: Optic gliomas are low-grade tumors of childhood and are frequently associated with an inherited condition called neurofibromatosis-type 1. These tumors, which arise from the optic nerve, can sometimes be treated successfully by surgery. At other times radiation therapy or chemotherapy may be required. The tumors are rarely lethal but may cause substantial visual loss.

Ganglioglioma: This tumor contains both mature neurons and glial cells. It has a high rate of cure by surgery alone or surgery combined with radiation therapy.

Primitive neuroectodermal tumors: Almost one fourth of brain tumors in children are of this type. They are rare in adults. When these arise in the cerebellum, they are called medulloblastomas. They are fast-growing tumors that can spread along the spinal cord and meninges but can be treated. Up to 50% of cases are cured by surgery and radiation therapy, sometimes with added chemotherapy. About 15% of childhood brain tumors are medulloblastomas.

Primitive neuroectodermal tumors are called pineoblastomas when they occur in the pineal gland. Other forms of primitive neuroectodermal tumors are all rapidly growing tumors that frequently spread throughout the cerebrospinal fluid pathways. The outlook for pineoblastomas is not as favorable as for medulloblastomas.

Ependymomas: Almost 10% of brain tumors in children are ependymomas. These tumors arise from the ependymal cells that line the ventricles or central canal of the spinal cord. Ependymomas may block the exit of cerebrospinal fluid from the ventricles causing the ventricle to become very large - a condition called hydrocephalus. Unlike astrocytomas and oligodendrogliomas, ependymomas usually do not spread or infiltrate into normal brain tissue. As a result, some but not all ependymomas can be removed and cured by surgery. Spinal cord ependymomas have the greatest chance of surgical cure. Ependymomas may spread along the cerebrospinal fluid pathways but do not spread outside the brain or spinal cord. Ependymomas represent about 9% of childhood brain tumors.

Choroid plexus tumors: These tumors arise in the choroid plexus within the ventricles of the brain. They are usually benign and cured by surgery (choroid plexus papillomas). However, they may also be malignant (choroid plexus carcinomas).

Craniopharyngioma: This type of tumor arises above the pituitary gland but below the brain itself. Most craniopharyngiomas are very close to the optic nerve, making surgical removal difficult, because of possible damage to the childÂ's vision. They may also compress the pituitary gland and the hypothalamus causing hormonal problems. Some are cured by surgery; others require radiation therapy.

Schwannoma (neurilemoma): This type of tumor starts in Schwann cells that surround and insulate cranial nerves and other nerves. Schwannomas are usually benign tumors that often form near the cerebellum and in the cranial nerve, which is responsible for hearing and balance. They also arise from spinal nerves after they have left the spinal cord and can compress the spinal cord causing weakness, sensory loss, and bowel and bladder problems. These tumors are rare in children and when present in this age group, particularly if there is more than one, might suggest an inherited familial tumor syndrome such as neurofibromatosis.

Meningioma: This type of tumor arises from the meninges, the tissue that surrounds the outer part of the brain and spinal cord. Meningiomas cause symptoms by pressing on the brain or spinal cord. Meningiomas are much less common in children than in adults.

Meningiomas are benign and are usually cured by surgery. Some meningiomas, however, are located dangerously close to vital structures within the brain and cannot be cured by surgery. Meningiosarcomas are rare but very malignant (cancerous) tumors that may come back many times after surgery or, in rare occasions, spread to other parts of the body.

Chordoma: This tumor starts in the bone at the back of the skull or at the lower end of the spinal column. Chordomas may come back many times over a period of 10 to 20 years causing progressive neurologic damage and deterioration. But they usually do not spread or metastasize to other organs.

Germ cell tumors: Germ cell tumors develop from germ cells that normally form eggs in women and sperm in men. During normal embryonic and fetal development, germ cells migrate to the ovaries or testicles and develop into eggs or sperm cells. Sometimes, however, a few germ cells may not migrate properly and end up in abnormal locations such as the brain. They may then develop into germ cell tumors similar to those that can form in the ovaries or testicles.

Germ cell tumors of the nervous system usually occur in children, most often in the pineal gland or above the pituitary gland. The most common germ cell tumor of the nervous system is the germinoma, which can be cured by radiation therapy and possibly chemotherapy in almost all cases. Other tumors of germ cell origin such as choriocarcinoma or yolk sac tumors are rarely cured by surgery. Both radiation therapy and chemotherapy are used in their treatment and in some cases this may not control the tumor completely. Germ cell tumors can sometimes be diagnosed without a biopsy by measuring certain chemicals in the cerebrospinal fluid or blood.

Neuroblastoma: Another kind of nerve cell tumor, which is not a brain tumor, is called neuroblastoma. This is the third most common cancer in children. Neuroblastomas rarely develop in the brain or spinal cord; most develop from nerve cells inside the abdomen or chest. This type of cancer is most commonly diagnosed during early infancy. Neuroblastoma is discussed in a separate American Cancer Society document.

Revised: 09/19/2005

WHAT IS CHILDHOOD LEUKEMIA?

LEUKEMIA DEFINED

AMERICAN CANCER SOCIETY: Detailed Guide: Leukemia - Children's
What Is Childhood Leukemia?

Leukemia is a cancer of the early blood-forming cells. Usually, the leukemia is a cancer of the white blood cells, but leukemia can involve other blood cell types as well.

Leukemia starts in the bone marrow and then spreads to the blood. From there it can go to the lymph nodes, spleen, liver, central nervous system (the brain and spinal cord), testes (testicles), or other organs.

Some childhood cancers, such as neuroblastoma or Wilms tumor, start in other organs and can spread to bone marrow, but these cancers are not leukemia.

Bone Marrow

The bone marrow is the inner part of bones. It is where blood cells (red blood cells, white blood cells and platelets) are produced. In infants, active bone marrow is found in almost all bones of the body, but by the teenage years, it is found mainly in the flat bones (skull, shoulder blade, ribs, pelvis) and vertebrae (back bones).

Bone marrow is made up of blood-forming (hematopoietic) cells and supporting tissues that help blood-forming cells grow. The earliest blood-forming cells are called stem cells. These cells can either divide to produce more stem cells or grow into other blood cells. But first, they develop into two early types of cells. These are the lymphoid cells that produce lymphocytes and can turn into acute lymphocytic leukemia and myeloid cells that form red blood cells, white blood cells, and platelets and that can turn into acute myeloid leukemia.

Red blood cells

Red blood cells carry oxygen from the lungs to all other tissues of the body. When the marrow does not produce enough red blood cells to replace those wearing out, a condition known as anemia (too few red blood cells in the body) can result. Anemia typically causes weakness, tiredness, and shortness of breath.

Platelets

Platelets are fragments that break off from a type of bone marrow cell called a megakaryocyte and are released into the bloodstream. Platelets are important because they plug areas of damage to small blood vessels caused by cuts or bruises. Not having enough platelets is called thrombocytopenia and can result in excessive bleeding and bruising.

White blood cells

White blood cells, also known as leukocytes, defend the body against infections with bacteria, viruses, and fungi (germs). The 3 main types of white blood cells are lymphocytes (discussed in the section on lymphoid tissue), granulocytes, and monocytes.

Lymphocytes, are the main cells that make up lymphoid tissue also known as lymphatic tissue. Lymphoid tissue is the main component of the immune system. It is formed by several different types of cells that work together to resist infection. Lymphoid tissue and the immune system may also fight some types of cancers. This system also reacts to tissues received from other people, such as blood transfusions or organ transplants.

Lymphoid tissue is found in many places throughout the body, including the lymph nodes, thymus, spleen, tonsils and adenoids, and bone marrow. It is also scattered within other systems, such as the digestive system and respiratory system. There is an extensive interconnecting system between all lymphoid tissues called the lymphatic system. Lymphocytes circulate in this system and eventually flow into the bloodstream.

The lymphocyte is the main cell type that forms lymphoid tissue. These are the cells from which acute lymphocytic (or lymphoblastic) leukemia develops.

There are 2 main types of lymphocytes:

B lymphocytes (B cells)
T lymphocytes (T cells)
Although both can develop into leukemia, B-cell leukemias are much more common than T-cell leukemias.

Normal T cells and B cells do different jobs in the immune system.

B cells help protect the body against bacteria and viruses by maturing into plasma cells and producing immunoglobulins (antibodies). Antibodies attach to certain chemicals on the surface of a germ. This attracts another type of cell (the granulocyte, discussed above), which digests the antibody-coated germ. Antibodies also attract certain proteins that can destroy bacteria by punching holes in them.

T cells help protect us against foreign substances (those not normally present in the body). They recognize specific chemicals, such as those found on the outside of virus-infected cells. They then destroy these cells by releasing substances that cause them to develop holes and become leaky. T cells can also release substances called cytokines that attract other types of white blood cells, such as macrophages, which then surround and digest the infected cells.

T cells are also thought to destroy some types of cancer cells as well as the cells of transplanted organs. Patients with transplanted organs must take special medication to prevent this action by T cells.

Normal B cells and T cells can be recognized by laboratory tests that identify distinctive chemicals on their surfaces. Some chemical substances are found only on B cells, and others are found only on T cells.

There are actually several types of T cells, each with a specialized job to do. There are also several stages of B-cell and T-cell development or maturation that can be recognized. This is important because leukemias that arise from these cells tend to resemble a particular subtype of normal lymphocyte at a certain level of development.

Normal lymph nodes are bean-sized organs located throughout the body and connected by a system of lymphatic vessels. These vessels are like thin veins, except that instead of carrying blood, they carry lymph. Lymph is a clear fluid containing waste products and excess fluid from tissues, as well as immune system cells traveling between lymph nodes and other organs.

Lymph nodes enlarge when they are fighting an infection, especially in infants and children. Lymph nodes that grow during a reaction to infection are called reactive nodes or hyperplastic nodes. An enlarged lymph node is not usually serious in a child. But a large lymph node may sometimes be a sign of leukemia.

The spleen is located under the lower part of the rib cage, on the left side of the body. It is the largest collection of lymph tissue in the body. The spleen produces lymphocytes and other immune system cells to help fight infections. It also stores healthy blood cells and filters out damaged blood cells, bacteria, and cell waste. If certain diseases cause the bone marrow to stop producing blood cells, the spleen may function in a back-up role for this task.

The thymus gland is an organ located in front of the heart. Before birth, this gland plays a vital role in development of the T lymphocytes, which are important to the immune system. Although the thymus gland's size and importance peak early in childhood, it continues to function in the immune system throughout life.

Adenoids and tonsils are collections of lymphoid tissue located at the back of the throat. They are easy to see when they become enlarged during an infection or if they become cancerous.

Granulocytes come from an early cell called the myeloblast. This is the malignant cell in acute myeloid leukemia. Granulocytes destroy germs such as bacteria. The main type of granulocyte is called a neutrophil or polymorphonuclear leukocyte (poly for short). Two other types are basophils, and eosinophils. They are all distinguished by the size and color of their granules (spots seen inside the cells under the microscope). These granules contain chemicals that help fight invading microorganisms. Granulocytes undergo several changes as they mature from a primitive myeloblast to infection-fighting cells. Once released into the bloodstream as mature cells, they circulate for only a short period of time (usually just a few hours), so they must be constantly replaced.

Monocytes also protect the body against microorganisms. After circulating in the bloodstream, they enter tissues to become macrophages, which can destroy some germs by surrounding and digesting them. Macrophages also help lymphocytes recognize germs so they can make antibodies to fight them.

Types of Leukemia in Children

Leukemia is described as being acute (rapidly growing) or chronic (slowly growing). Almost all childhood leukemia is acute.

There are 2 types of acute leukemia:

Acute lymphocytic leukemia (ALL, also called acute lymphoblastic leukemia). This leukemia starts from the lymphoid cells in the bone marrow.

Acute myelogenous leukemia (AML, also called acute myeloid leukemia, acute myelocytic leukemia, or acute non-lymphocytic leukemia [ANLL]). This leukemia starts from the cells that form red cells, white cells, and platelets.
Chronic leukemias can also be divided into two types - chronic lymphocytic leukemia (CLL) and chronic myelogenous leukemia (CML). These forms of leukemia are very rare in children and are not discussed in this document. But chronic myeloid leukemia does occur in children. It is treated the same as in adults. For more information see the ACS document on chronic myeloid leukemia.

There is another rare type of leukemia that is neither chronic nor acute, called juvenile myelomonocytic leukemia. It begins from myeloid cells, but isn't as fast growing as acute myelogenous leukemia or as slow as chronic myeloid leukemia. These children usually have a high white blood cell count and enlarged spleen

Leukemias are classified by how the cells look under the microscope along with special chemical and genetic tests. To help doctors see them clearly, the cells are examined with special stains or dyes that change the color of different parts of the cells. Although some leukemias can be easily classified by routine stains, most require special cytochemical stains that help identify certain substances inside the leukemic cells.

Often more complex testing is needed to decide on the exact type of leukemia a child has. This is important, because different types of leukemia have a different prognosis (survival outlook) and are treated differently. Tests used to further classify leukemias include:

flow cytometry: a test that uses special antibodies to detect specific substances on the cell surface or inside the cell.

cytogenetic tests: studies to detect changes in the chromosomes of cells.

molecular genetic tests: tests that show changes in the cell's DNA.
These tests are done on samples of leukemic cells from a child's blood or bone marrow, and are described in the section How Is Childhood Acute Leukemia Diagnosed?

Acute Lymphocytic Leukemia (ALL)

Acute lymphocytic leukemia (ALL) is a cancer of the lymphocyte-forming cells called lymphoblasts. In the past, ALL was divided into 3 major categories (L1, L2, or L3) based on its morphology (appearance under the microscope).

L1 is the most common type in children. The lymphoblasts are small cells.
L2 accounts for 10% of ALL cases. These cells are larger.
L3 is the rarest subtype.
This system is no longer used because there are better ways of classifying ALL than how it looks under the microscope. We include it here because some doctors may still refer to these categories. It is more useful to classify types of ALL by looking for certain substances, called antigens, in the cells. Tests for abnormalities in the genes and chromosomes of leukemia cells are also used to determine their type.

The leukemias are also further classified by their B- or T-cell status.

Type Frequency
Early Pre-B 57%-65%
Pre-B 20%-25%
B Cell 2%-3%
T Cell 13%-15%

B-cell ALL: About 85% of ALL is B-cell ALL. The most common subtype of B-cell ALL is "early precursor B" (early pre-B) ALL.

The second B-cell leukemia subtype is the "pre-B" form of ALL. This form of ALL accounts for 20% to 25% of patients with B-cell ALL. The third and least common type of B-cell ALL is mature B-cell leukemia. This accounts for about 2% to 3% of childhood ALL. It is also called Burkitt leukemia. Because this disease is essentially the same as Burkitt lymphoma and is treated differently than most leukemias, it is discussed in detail in our document "Childhood Non-Hodgkin Lymphoma".

T-cell ALL: About 13% to 15% of children with ALL have T-cell ALL. This type of leukemia affects boys more than girls, and generally affects older children than does B-cell ALL. It is often associated with an enlarged thymus (which can sometimes cause breathing difficulty) and with early spread to the cerebrospinal fluid (the fluid that surrounds the brain and spinal cord).

Acute Myelogenous Leukemia (AML)

Acute myelogenous leukemia (AML) is a cancer of one of the following types of early (immature) bone marrow cells:

myeloblasts - these cells normally form granulocytes
monoblasts - these cells normally become monocytes
erythroblasts - these cells mature into red blood cells
megakaryoblasts - these cells normally become megakaryocytes, the cells that make platelets
AML has several subtypes, depending on which type of these early cells develops into cancer. Although tests are often helpful in identifying AML, the subtypes of AML are classified almost exclusively by their morphology (appearance under the microscope), using routine and cytochemical stains. But more careful chemical testing may be useful to better determine the leukemia type. It is also useful to look for abnormalities in the chromosomes of the leukemia cells. Also, as it becomes more widely available, most doctors are turning to genetic testing to help classify leukemia.

There are 8 subtypes of AML: M0 to M7 (the "M" refers to myeloid).

M0 - This subtype of AML is made up of very immature cells. It can only be distinguished from ALL by flow cytometry because the leukemic cells lack any distinctive features that can be seen by microscope. (flow cytometry is explained in the section, "How Is Childhood Leukemia Diagnosed?").

M1, M2, and M3 - These subtypes of AML are leukemias of granulocytes and can be recognized by the way they look under the microscope, particularly after applying cytochemical stains. The M3 subtype is known as acute promyelocytic leukemia (APL), and is treated differently from other types of AML.

M4 and M5 - These are two forms of monocytic leukemia. These 2 types of AML are more likely to occur in children less than 2 years of age.

M6 - This subtype of AML is known as erythroleukemia. It develops in erythroblasts, the cells that normally mature into red blood cells. It is very rare in children.

M7 - This subtype is made up of megakaryocytic leukemia cells and may show a unique "budding" resembling the way platelets normally form from normal megakaryocytes.
Hybrid or Mixed Lineage Leukemias

Some leukemias have features of both ALL and AML when the cells are viewed under a microscope and tested by flow cytometry or cytogenetic tests. They are generally treated like ALL and respond to treatment like ALL.

Revised: 03/06/2006

WHAT IS NEUROBLASTOMA?

NEUROBLASTOMA DEFINED

AMERICAN CANCER SOCIETY: Detailed Guide: Neuroblastoma
What Is Neuroblastoma?

Neuroblastoma is a form of cancer that occurs in infants and young children. It is rarely found in children older than 10 years. The cells of this cancer usually resemble very primitive developing nerve cells found in an embryo or fetus. (The term neuro indicates "nerves," while blastoma refers to a cancer that affects immature or developing cells).

Neurons (nerve cells) are the main component of the brain and spinal cord and of the nerves that connect them to the rest of the body. These cells are essential for thinking, sensation, and movement. There is a part of the nervous system that we are rarely aware of, called the autonomic nervous system, which controls involuntary body functions such as heart rate, blood pressure, and digestion. The sympathetic nervous system is a part of the autonomic nervous system. It includes:

nerve fibers that run alongside the spinal cord
clusters of nerve cells called ganglia (plural of ganglion) at certain points along the path of the nerve fibers
nerve-like cells found in the medulla (center) of the adrenal glands. The adrenals are triangular-shaped glands located above the kidneys. The hormone adrenaline comes from the cells in the adrenal gland.
Most neuroblastomas (about two thirds) start in the abdomen. About one third of neuroblastomas start in the adrenal glands and another third begin in the sympathetic nervous system ganglia of the abdomen. The rest start in sympathetic ganglia of the chest or neck or in the pelvis. Some can start in the spinal cord. Rarely, a neuroblastoma may have spread so extensively by the time it is found that doctors are unable to determine exactly where it started.

Not all childhood autonomic nervous system tumors are malignant (cancerous). There is a benign tumor called ganglioneuroma which is composed of mature ganglion and nerve sheaths that do not continue to grow.

Ganglioneuroblastoma is a tumor that has both malignant and benign parts. It contains neuroblasts (immature nerve cells) that can grow and spread abnormally, as well as areas of benign tissue that are similar to ganglioneuroma.

Ganglioneuromas are usually removed by surgery and carefully examined under a microscope to be certain they do not have areas of ganglioneuroblastoma. If the final diagnosis is ganglioneuroma, no additional treatment is needed. In contrast, ganglioneuroblastomas are treated the same as neuroblastomas (see "How Is Neuroblastoma Treated?").

Neuroblastoma is a unique cancer in many ways. It is one of the few cancers in children that release hormones that can cause strange changes in the body, such as constant diarrhea. It can also cause changes in the some functions of the brain, such as opsoclonus (rotary movements of the eyes) and myoclonus (spastic jerks of the muscles).

These changes are called paraneoplastic syndromes.

The tumor itself can behave strangely. Sometimes the cells die without any cause and the tumor disappears. This is part of a normal process known as programmed cell death (apoptosis), the normal process that occurs when cells die. This tumor disappearance is much more common in very young infants than in older children. Another behavior that is unusual for childhood tumors is that the cells sometimes mature spontaneously to normal ganglion cells and stop dividing. This causes the tumor to become a ganglioneuroma, which is benign (non-cancerous).

Revised: 08/04/2006

WHAT IS NON-HODGKIN
LYMPHOMA IN CHILDREN?

WHAT IS NON-HODGKIN LYMPHOMA IN CHILDREN?

NON-HODGKIN LYMPHOMA IN CHILDREN DEFINED

AMERICAN CANCER SOCIETY: Detailed Guide: Childhood Non-Hodgkin's Lymphoma
What Is Non-Hodgkin Lymphoma in Children?

Lymphoma is the third most common childhood cancer. Lymphomas are divided into 2 main types. The first is called Hodgkin lymphoma or Hodgkin disease (also known as Hodgkin's lymphoma or Hodgkin's disease), which is named after Dr. Thomas Hodgkin, who first described it in 1832. All other types of lymphoma are called non-Hodgkin lymphoma (non-Hodgkin's lymphoma). These 2 types of lymphomas differ in their behavior, pathology, spread, and responsiveness to treatment.

Non-Hodgkin lymphoma (NHL) and Hodgkin disease (HD) occur about equally in children younger than 20 years old. Non-Hodgkin lymphoma usually occurs in younger children while Hodgkin disease is more a disease of older children and adolescents. This document discusses only non-Hodgkin lymphoma. For information on childhood Hodgkin disease, see the American Cancer Society document Hodgkin Disease.

Lymphoma is a type of cancer that starts in lymphoid tissue. Other types of cancer can develop in other organs of children and adults and then spread to lymphoid tissue. For example, childhood cancers such as neuroblastoma or Wilms tumor can spread to lymph nodes, but these cancers are not lymphomas.

What Is Lymphoid Tissue?

Lymphoid tissue, also known as lymphatic tissue, is formed by several types of immune system cells that work together to resist infections. Lymphoid tissue is found in many places throughout the body. These are described below.

The main cell type found in lymphoid tissue is the lymphocyte, a type of white blood cell. The 2 main types of lymphocytes are B lymphocytes (B cells) and T lymphocytes (T cells). Although both types of cells can develop into lymphomas, B-cell lymphomas are more common than T-cell lymphomas.

Normal T cells and B cells do different jobs within the immune system. B cells help protect the body against bacteria or viruses by producing antibodies. Antibodies attach to the surface of the bacteria or viruses, which signals other parts of the immune system to get rid of the antibody-coated germ.

There are several types of T cells, each with a specific job. Some normal T cells help protect the body against viruses, fungi, and some bacteria, such as those causing tuberculosis. They recognize specific substances found in virus-infected cells and destroy these cells. T cells can also release substances called cytokines that attract other types of white blood cells, which then digest the infected cells. T cells are also thought to destroy some types of cancer cells, as well as the cells of transplanted organs. Some types of T cells play a role in stimulating or inhibiting the activity of other immune system cells.

Normal B cells and T cells can be recognized by laboratory tests that identify distinctive substances on their surfaces. Certain substances are found only on B cells, and others are found only on T cells. There are also several stages of B-cell and T-cell development (maturation) that can be recognized.

This information on types of lymphocytes is helpful to know because each type of lymphoma tends to resemble a particular subtype of normal lymphocyte at a certain level of development. Determining the type of lymphoma a person has is the first step in considering treatment options.

Organs that Contain Lymphoid Tissue

Lymph nodes are bean-sized organs located throughout the body and connected by a system of lymphatic vessels. These vessels are like veins, except that instead of carrying blood, they carry lymph (a clear fluid containing waste products and excess fluid from tissues) and immune system cells traveling to lymph nodes from other tissues.

Lymph nodes increase in size when they fight an infection, especially in children. Lymph nodes that grow in reaction to infection are called reactive nodes or hyperplastic nodes and are often tender to the touch. An enlarged lymph node in a child is not usually serious. However, a large lymph node is also the most common sign of lymphoma. Lymph node enlargement is discussed more in the section "How Is Childhood Non-Hodgkin Lymphoma Diagnosed?"

The spleen is found under the lower part of the rib cage on the left side of the body. An average adult spleen weighs about 5 ounces, whereas the spleen of a 10-year-old is about 3 ounces. It is the largest collection of lymph tissue in the body. The spleen produces lymphocytes to help fight infection, stores healthy blood cells, and filters out damaged blood cells, bacteria, and cell waste.

The thymus gland is an organ located in front of the heart. Even before birth, this gland plays a vital role in development of the T cells. The thymus gland's size (about 1 ounce) and importance peak between the ages of 1 and 20 years old. Although its size and role decline with age, the thymus continues to play a role in immune system function throughout life.

Adenoids and tonsils are collections of lymphoid tissue located at the back of the throat. They produce antibodies against germs that are breathed in or swallowed. They are easy to see when they become enlarged during an infection, which occurs often in children, or if a lymphoma develops.

The stomach and intestinal tract as well as many other organs also contain lymphoid tissue.

Bone marrow (the soft inner part of bones) produces red blood cells, blood platelets, and white blood cells. Red blood cells carry oxygen from the lungs to the rest of the body. Platelets plug up small holes in blood vessels caused by cuts or scrapes. White blood cells' main job is fighting infections. The 2 main types of white blood cells are granulocytes and lymphocytes. Sometimes lymphomas can start from bone marrow lymphocytes. Another cancer that starts from bone marrow lymphocytes is leukemia. Sometimes these 2 cancers are very similar and can be treated the same way.

Types of Non-Hodgkin Lymphoma Commonly Affecting Children

Lymphomas are most often classified by how the cancer cells look under the microscope (their size and shape) and their pattern of growth within the lymph node. Size is described as large or small, and shape is described as cleaved (showing folds or indentations) or non-cleaved. The growth pattern may be either diffuse (scattered) or follicular (arranged in clusters of cells). The latter is very rare in children.

Not every lymphoma is described using all 3 features (size, shape, and pattern). For example, lymphomas might be described as small cleaved cell type, diffuse mixed (small and large) cell type, large cell, or small non-cleaved cell type. Additional laboratory tests are often needed to accurately classify lymphomas. These are discussed in the section "How Is Childhood Non-Hodgkin Lymphoma Diagnosed?"

Nearly all non-Hodgkin lymphomas in children belong to 1 of 3 types:

lymphoblastic lymphoma
small non-cleaved cell (Burkitt) lymphoma
large cell lymphoma
Although all 3 types are high grade (meaning they grow rapidly) and diffuse, it is important to distinguish among them because their treatment is very different. A fourth less common type is called large cell anaplastic lymphoma. It is treated the same as large cell lymphoma.

Lymphoblastic lymphoma: Lymphoblastic lymphoma accounts for about 30% of lymphomas in children. The median age for children is about 9 years, which means that half the children are younger than 9 and the other half older than 9. It is most common in teenagers, and boys are affected twice as often as girls. Most cases of lymphoblastic lymphoma develop from T cells in the thymus and form a mass in the anterior mediastinum (the area behind the breast bone). This mass can interfere with breathing. Difficulty with breathing may be the first symptom of lymphoblastic lymphoma.

Less often, this cancer may develop in the tonsils, lymph nodes of the neck, or other lymph nodes. Lymphoblastic lymphoma can spread very quickly to the bone marrow, other lymph nodes, the surface of the brain, and/or the membranes that surround the lungs and heart.

The malignant (cancerous) cells of this lymphoma are the same as those in acute lymphoblastic leukemia (ALL) in children. If more than 25% of the bone marrow is involved, the disease is reclassified as leukemia and treated as leukemia.

Because lymphoblastic lymphoma can be a very rapidly growing disease and can interfere with breathing, it needs to be diagnosed and treated quickly.

A small fraction of lymphoblastic lymphomas develop from B-cells. These lymphomas more often begin in lymph nodes outside the chest, particularly in the neck. They can also involve the skin and bones.

Small non-cleaved non-Hodgkin lymphoma (Burkitt and non-Burkitt): Small non-cleaved non-Hodgkin lymphoma accounts for about 40% to 50% of childhood non-Hodgkin lymphoma in the United States. It is most often seen in boys, usually around the age of 5 to 10 years old.

There are 2 types of small non-cleaved non-Hodgkin lymphoma: Burkitt type (also called Burkitt's lymphoma -- after Dr. Denis Burkitt who described this lymphoma in African children) and non-Burkitt type. However, children with either type are treated the same.

In certain areas of Africa, the Burkitt-type small non-cleaved lymphoma accounts for nearly all childhood non-Hodgkin lymphoma and over half of all childhood cancers. For reasons that are not understood, small non-cleaved lymphoma of African children usually develops in the jaws or other facial bones.

Small non-cleaved lymphomas in other areas of the world, including the United States almost always start in the abdomen. A typical child will develop a large tumor in his or her abdomen that can sometimes block the bowel. This can cause abdominal pain, nausea and vomiting. This lymphoma can sometimes start in the neck or tonsils, or more rarely in almost any other part of the body.

This lymphoma develops from B lymphocytes, and it is one of the most rapidly growing cancers known. It may spread to other organs, including the surface of the brain or inside the brain. Because of this, it must be diagnosed and treated quickly.

Large cell and anaplastic non-Hodgkin lymphoma: Large cell non-Hodgkin lymphoma represents about 25% of all non-Hodgkin lymphoma in children. The main subtypes are diffuse large B-cell lymphoma, mediastinal large B-cell lymphoma (mediastinal lymphomas arise in the center of the chest), and anaplastic large cell lymphoma. Some doctors group anaplastic large cell lymphoma with large cell lymphoma, but they arise from different cells. Anaplastic large cell lymphoma usually develops from T cells, while the other 2 types usually develop from B cells. Treatment of the anaplastic type is the same as for the other large cell lymphomas, but the cure rate tends to be slightly lower.

Large cell lymphoma may develop in the lymphoid tissue of the neck, mediastinum (area behind the breast bone), throat, or abdomen. Early spread to the skin or tissues under the skin is not unusual. This type of lymphoma is not as likely to spread to the bone marrow or brain, nor does it grow as rapidly as other childhood lymphomas.

Revised: 03/08/2007

WHAT IS RETINOBLASTOMA?

RETINOBLASTOMA DEFINED

AMERICAN CANCER SOCIETY: Detailed Guide: Retinoblastoma
What Is Retinoblastoma?

Most kinds of cancer are named for the place where the cancer starts. Retinoblastoma starts in the retina, the very back portion of the eye. Retinoblastoma is the only common type of eye cancer in children. Rarely, children can have other kinds of eye cancer. The information here applies only to retinoblastoma and not to other kinds of eye cancer.

The eye consists of a sphere called the globe, which is filled with a gelatinous material called vitreous; a lens with an iris (the colored part of the eye that acts like a camera shutter) on the front; and the retina in the back. The lens and the iris focus incoming light on the retina. The retina is like the sensor array in the back of a digital camera.

The retina is connected to the brain (the "memory" in a digital camera) by the optic nerve. The pattern of light appearing on the retina is transmitted from the retina to the brain, allowing us to see. The eyes develop very early as babies grow in the womb. During the early stages of development, the eyes contain cells called retinoblasts that divide into new cells and fill the retina. Later on, the cells stop dividing and develop into mature retinal cells.

Rarely, something goes wrong during development of retinal cells. Instead of developing into cells specialized for detecting light, some retinoblasts continue to grow rapidly and out-of-control, and form a cancer known as retinoblastoma. The sequence of events that lead to the development of retinoblastoma is rather complex, but it is always started by an abnormality (mutation) in a gene called the retinoblastoma gene. About one-third of the time, this abnormality is congenital (present at birth) and it is present in all the cells of the body (and therefore in all the cells of both retinas), and two-thirds of the time the abnormality in the retinoblastoma gene develops on its own only in one cell in one eye without a known cause. In the first form of retinoblastoma (where the child is born with the mutation) there may not always be a family history of this cancer; in fact, only 25% of the children born with this abnormality have an affected parent, whereas 75% of them acquire this abnormality while in the womb.

The 2 different types of abnormalities (all cells in the body or only one cell in the eye) lead to 2 different forms of retinoblastoma. In the first one, children born with the genetic defect develop more than one retinoblastoma, usually in both eyes (bilateral or multifocal retinoblastoma). Also, within the eyes there are often several small tumors (multifocal retinoblastoma). In the second form, children develop only one tumor (unilateral and unifocal retinoblastoma). These 2 forms are treated very differently.

If growth of these cells is not controlled by treatment, they can form a tumor that fills much of the globe (eyeball). The cells may break away from the retinal tumor and float through the vitreous to reach other parts of the eye, where they form more tumors. If these tumors block the channels that are important in circulation of fluid within the eye, the pressure inside the eye can rise, resulting in glaucoma. Glaucoma is one of the serious complications of retinoblastoma that can lead to pain and loss of vision in the affected eye.

Most retinoblastomas are found and treated before they have spread outside the globe. But retinoblastoma cells can occasionally spread to other parts of the body. The cells sometimes grow along the optic nerve to reach the brain. Retinoblastoma cells can also grow through the covering layers of the globe into the eye socket, eyelids, and nearby tissues. Once tissues outside the globe are affected, the cancer may then spread to lymph nodes (small bean-shaped collections of immune system cells) and to internal organs and to bones.

Revised: 07/06/2006

WHAT IS WILMS TUMOR?

WILMS TUMOR DEFINED

AMERICAN CANCER SOCIETY: Detailed Guide: Wilms Tumor
What Is Wilms Tumor?

Wilms tumor (also called Wilms' tumor or nephroblastoma) is the most common type of kidney cancer that affects children. It is named after Max Wilms, a German doctor who wrote one of the first medical articles about the disease in 1899.

About the Kidneys

The kidneys are 2 curved organs fixed to the back wall of the abdominal cavity. Each kidney is about the size of a fist. One kidney is just to the left and the other just to the right of the backbone. The lower rib cage protects the kidneys.

The kidneys' main job is to filter the blood and rid the body of excess water, salt, and waste products in the form of urine. To do this, a kidney has millions of specialized structures called glomeruli. These structures do the filtering. Each glomerulus is connected to a wavy tube called a nephron that collects and concentrates the filtered fluid, which then becomes urine. Urine leaves the kidneys through long slender tubes called ureters. Each kidney has a single ureter that empties into the bladder where urine is stored until you urinate. Although our kidneys are important, we actually need less than 1 complete kidney to do all of the vital functions discussed above. Tens of thousands of people in the United States are living normal healthy lives with just 1 kidney.

Types of Wilms Tumor

Wilms tumors usually affect only 1 kidney (unilateral). But about 5% of children with Wilms tumor have this cancer in both kidneys (bilateral).

Most Wilms tumors are found only after they have become quite large. They are usually found before they metastasize (spread to other organs). The average weight of a newly found Wilms tumor is about 1 pound - many times larger than the kidney in which it developed.

Even though doctors may think a child has a cancer such as Wilms tumor, they cannot be certain until the pathologist (a doctor who specializes in diagnosis and classification of diseases by lab tests such as examining cells under a microscope) looks at the tumor under the microscope. Wilms tumors are classified into 2 major types depending on how they look under the microscope (also known as histology):

Wilms tumor with a favorable appearance under the microscope
Wilms tumor with an unfavorable appearance under the microscope
A tumor has an unfavorable appearance (unfavorable histology) when the nuclei (the central part of the cell that contains the DNA) of the cancer cells are very large and distorted. Also, the cells are not uniform and their appearance varies widely. This is called anaplasia. The more anaplasia that is found, the poorer the chance is for a cure. Favorable appearance (favorable histology) means there is no anaplasia and the chance of cure is very good. About 95% of Wilms tumors have a favorable histology.

Other Types of Kidney Cancer

About 90% of kidney cancers that occur in children are Wilms tumors. Nearly all kidney cancers in adults are a different kind of cancer called renal cell carcinomas. Very rarely, adults may develop Wilms tumors or children may develop renal cell carcinoma.

In addition to Wilms tumors, there are several rare types of kidney tumors that affect children. One type, which is benign (not cancerous), is called mesoblastic nephroma. There are 2 other malignant (cancerous) tumors of the kidney in children. One is called clear cell sarcoma of kidney (CCSK) and the other is called rhabdoid tumor. These types tend to have a poor prognosis (outlook for cure) if the cancer has spread beyond the kidney. They were once classified as types of Wilms tumors of unfavorable histology but are now classified separately. They get the same treatment as Wilms' tumors except more intensively.

The rest of this document refers only to Wilms tumor.

Revised: 02/12/2006

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