Cancer is the catchall term applied to diseases caused by the uncontrolled growth of abnormal cells. Cancer isn't one disease. It is many different diseases, more than 100 and counting.
Each kind of cancer is usually named for the cell type in which it begins — cancer that starts in a lung is called lung cancer; cancer that starts in pigment cells in the skin, which are known as melanocytes, is called melanoma.
When detected and treated early, cancer can often be stopped. That said, cancer is a leading cause of death and disability around the world.
Doctors can diagnose many problems that cause anemia, some infections, and some kinds of leukemia or lymphoma cancers by examining a sample of your bone marrow. Bone marrow is the tissue where blood cells are made. A bone marrow biopsy is the procedure to collect such a sample. It is done using a needle inserted through the outside surface of a bone and into the middle of the bone, where the marrow is.
This type of cancer occurs in the bladder — the organ that stores urine. The bladder has an inner lining surrounded by a layer of muscle. Bladder cancer begins in the inner lining of the bladder. It is usually discovered before it has spread past this lining.
An acoustic neuroma is a type of benign (noncancerous) brain tumor that grows on the vestibular nerve as it travels from the inner ear to the brainstem. It is one of the most common types of benign brain tumors. The first sign of one is usually hearing loss.
The cochleo-vestibular nerve (also called the eighth cranial nerve) is made up of three nerves that connect the inner ear to the brain. One branch — the cochlear nerve — carries hearing information. The other two branches — the inferior and superior vestibular nerves — carry balance information to the brain. The nerves are wrapped in a layer of specialized cells called Schwann cells. An acoustic neuroma — also called a vestibular schwannoma — is a tumor of those cells. If an acoustic neuroma is not diagnosed or treated it can grow large enough to press on important structures in the brainstem and cause major life threatening problems.
Melanoma is cancer of the cells ("melanocytes") that give skin its color. It develops when these cells change and reproduce aggressively. The number of cases of melanoma, the deadliest form of skin cancer, is increasing faster than any other cancer.
Doctors aren't sure why melanoma rates are soaring. It could be from spending too much time in the sun during outdoor activities. It could also be due to global changes, such as the depletion of the ozone, which absorbs many of the sun's harmful rays.
Your pattern of sun exposure appears to affect your risk of developing melanoma more than the total amount of sun exposure in your lifetime. Short bursts of intense sun seem most dangerous, especially if you get sunburned. Being out in the sun can cause changes (mutations) in skin cells' genes. Researchers have recently found several gene mutations shared by many melanoma tumor cells. It is likely that one or more of these mutations starts the cancer.
What Is It?
A brain tumor is a mass of abnormally growing cells in the brain or skull. It can be benign (noncancerous) or malignant (cancerous). Unlike other cancers, a cancer arising from brain tissue (a primary brain cancer) rarely spreads. Whether benign or malignant, all brain tumors are serious. A growing tumor eventually will compress and damage other structures in the brain.
There are two categories of brain tumors: primary and secondary. Primary tumors start in brain tissue, while secondary tumors spread to the brain from another area of the body. Primary tumors are classified by the tissue in which they begin:
Gliomas, the most common primary tumors, start in the brain's glial (supportive) tissue. There are several types of gliomas, and they can vary in their aggressiveness and response to treatment. Glioblastoma multiforme is a fast-growing, higher-grade tumor that can arise from a lower-grade glioma.
Medulloblastomas come from early embryonic cells and more commonly occur in children.
Meningiomas are related to cells in the membranes surrounding the brain and spinal cord. They are usually benign, but can come back (recur) after treatment.
Secondary tumors most commonly arise from the lungs or breast. Other cancers, especially melanoma (a type of skin cancer), renal cell cancer (a type of kidney cancer), and lymphoma (a cancer of the immune system) can spread to the brain. When this happens, the cancer is the same as the original cancer. For example, lung cancer that spreads to the brain is known as metastatic lung cancer, because the tumor's cells resemble abnormal lung cells. Secondary brain tumors are much more common than primary tumors.
Although brain tumors can occur at any age, they most commonly affect adults 40 to 70 years old and children 3 to 12 years of age. Whether the use of cellular phones contributes to the development of brain tumors, especially in children, has sparked debate. The issue is far from resolved, and additional research is needed.
Lymphoma is a cancer of the lymph (or lymphatic) system. It is part of the immune system. It collects and destroys invading organisms, such as bacteria and viruses, and abnormal cells. It protects the body from infection and disease.
Lymphedema is the buildup of fluid called lymph in the tissues under your skin when something blocks its normal flow. This causes swelling, most commonly in an arm or leg.
Lymph normally does an important job for your body. It carries foreign material and bacteria away from your skin and body tissues, and it circulates infection-fighting cells that are part of your immune system.
Lymphedema occurs when there is inadequate lymph drainage from the body, usually from a blockage in a lymph channel. Lymphatic fluid builds up underneath the skin and causes swelling. Most commonly lymphedema affects the arms or legs.
Swelling from lymphedema can look similar to the more common edema caused by leakage from tiny blood vessels under the skin.
In most cases of lymphedema, the lymphatic system has been injured so that the flow of lymph is blocked either temporarily or permanently. This is called secondary lymphedema. Common causes include:
Surgical damage — Surgical cuts and the removal of lymph nodes can interfere with normal lymph flow. Sometimes, lymphedema appears immediately after surgery and goes away quickly. In other cases, lymphedema develops from one month to 15 years after a surgical procedure. Lymphedema occurs quite often in women who have had multiple lymph nodes removed during surgery for breast cancer.
An infection involving the lymphatic vessels — An infection that involves the lymphatic vessels can be severe enough to cause lymphedema. In areas of the tropics and subtropics, such as South American, the Caribbean, Africa, Asia and the South Pacific, parasites are a common cause of lymphedema. Filariasis, a parasitic worm infection, blocks the lymph channels and causes swelling and thickening below the skin, usually in the legs.
Cancer — Lymphoma, a cancer that starts in the lymph nodes, or other types of cancer that spread to the lymph nodes may block lymph vessels.
Radiation therapy for cancer — This treatment can cause scar tissue to develop and block the lymphatic vessels.
When lymphedema occurs without any known injury or infection, it is called primary lymphedema. Doctors diagnose three types of primary lymphedema according to when symptoms first appear:
At birth — Also known as congenital lymphedema. Risk is higher in female newborns. The legs are affected more often than the arms. Usually both legs are swollen.
After birth but before age 36 — Usually, it is first noted during the early teenage years. This is the most common type of primary lymphedema.
Age 36 and older — This is the rarest type of primary lymphedema.
All three types of primary lymphedema are probably related to the abnormal development of lymph channels before birth. The difference is when in life they first cause swelling of the legs or arms.
Leukemia is a form of cancer that affects the body's ability to make healthy blood cells. It starts in the bone marrow, the soft center of various bones. This is where new blood cells are made. Blood cells include
Red blood cells, which carry oxygen from the lungs to the body's tissues and take carbon dioxide to the lungs to be exhaled
Platelets, which help blood clot
White blood cells, which help fight infections, viruses, and diseases.
Although cancer can affect red blood cells and platelets, leukemia generally refers to cancer of the white blood cells. The disease usually affects one of the two major types of white blood cells: lymphocytes and granulocytes. These cells circulate throughout the body to help the immune system fight off viruses, infections, and other invading organisms. Leukemias arising from lymphocytes are called lymphocytic leukemias; those from granulocytes are called myeloid, or myelogenous, leukemias.
A bone marrow transplant is a procedure used to treat certain types of cancer and some other diseases. Before the bone marrow transplant takes place, a person's bone marrow cells are destroyed with radiation or chemotherapy.
The cells that normally live in the bone marrow and that are responsible for making blood cells are then replaced. Bone marrow cells are blood cells that are located in the spongy center of bones.
Acute lymphocytic leukemia (ALL) is a cancer of the body's blood-making system. (It is also known as acute lymphoblastic leukemia and acute lymphoid leukemia.) The word "acute" refers to the fact that the disease can progress quickly. "Lymphocytic" means that the cancer develops from lymphocytes, a type of white blood cell.
Bone marrow, the soft inner part of bones, makes cells that circulate in the blood. They include white blood cells, red blood cells, and platelets. The two major types of white blood cells are myeloid cells and lymphoid cells. Lymphocytes form from lymphoid cells.
Normally, the bone marrow makes three types of infection-fighting lymphocytes:
B lymphocytes — These cells make antibodies to help protect the body from germs.
T lymphocytes — These cells can destroy virus-infected cells, foreign cells, and cancer cells. They also help make antibodies.
Natural killer cells — These cells can also kill cancer cells and viruses.
In ALL, the bone marrow makes too many immature lymphocytes. These lymphocytes, called blasts, contain abnormal genetic material. They cannot fight infections as well as normal cells. In addition, because these lymphocytes multiply quickly, they crowd out healthy white blood cells, red blood cells, and platelets in the blood and bone marrow. This may lead to infection, anemia, and easy bleeding.
ALL typically invades the blood quickly. It can involve other parts of the body, such as the lymph nodes, liver, spleen, brain and spinal cord (central nervous system), and testicles (testes).
Although it is rare, ALL is the most common cancer in children. It can affect children of any age, but most are diagnosed between 2 and 4 years old.
A few factors may increase a child's risk of developing ALL. These include
having a sibling with leukemia
exposure to x-rays before birth
exposure to radiation
past treatment with chemotherapy or other drugs that weaken the immune system
having certain inherited disorders, such as Down syndrome
having a specific genetic change (mutation).
Having one or more of these risk factors does not mean your child will develop ALL. Many children with the disease have no risk factors.
ALL has several subtypes. Subtypes depend on
whether the cancerous cells formed from B lymphocytes or T lymphocytes
your child's age
whether the cells have certain changes in their genetic material.