What is rhabdomyosarcoma?
Rhabdomyosarcoma is a cancerous tumor that originates in the soft tissues of the body, including the muscles, tendons, and connective tissues. The most common sites for this tumor to be found include the head, neck, bladder, vagina, arms, legs, and trunk. Rhabdomyosarcoma can also be found in places where skeletal muscles are absent or very small, such as in the prostate, middle ear, and bile duct system. The cancer cells associated with this disease can spread (metastasize) to other areas of the body.
Embryonal rhabdomyosarcoma, the most common type, usually occurs in children under 6 years of age. Alveolar rhabdomyosarcoma occurs in older children and accounts for about 20 percent of all cases.
Rhabdomyosarcoma accounts for about 3 percent of childhood cancers. In the US, about 350 children are diagnosed with rhabdomyosarcoma each year. This disease affects children between the ages of 2 to 20 years of age, but can occur at any age. For unknown reasons, males are affected slightly more often than females.
What causes rhabdomyosarcoma?
It is believed that some rhabdomyosarcoma tumors begin developing in the fetus. Rhabdomyoblasts are the cells at the initial stages of development of an unborn baby. These cells will mature and develop into muscles. There has been much research into the gene structure of these rhabdomyoblasts and possible detection of a gene error that can produce the disease later in development.
Rhabdomyosarcomas usually have some type of chromosome abnormality in the cells of the tumor, which are responsible for the tumor formation. In children with an embryonal rhabdomyosarcoma, there is usually an abnormality of chromosome #11. In alveolar rhabdomyosarcoma, a rearrangement in the chromosome material between chromosomes #2 and #13 is usually present. This rearrangement changes the position and function of genes, causing a fusion of genes referred to as a "fusion transcript." Patients have an abnormal fusion transcript involving two genes known as PAX3 and FKHR. This important discovery has led to improvements in diagnosing rhabdomyosarcoma.
Rhabdomyosarcomas are also more common in children with neurofibromatosis or Li-Fraumeni syndrome, which are genetic disorders. Li-Fraumeni syndrome is a clustering of soft tissue cancers in a family, caused by mutations in a tumor suppressor gene called p53, which results in uncontrolled cell growth.
There has been no association between rhabdomyosarcoma and environmental exposures.
There are three types of rhabdomyosarcoma:
- Embryonal rhabdomyosarcoma – This is the most common type of rhabdomyosarcoma, usually affects infants and young children, and generally occurs in the head and neck area, bladder, in or around the prostate and testes.
- Alveolar rhabdomyosarcoma – This type occurs in the large muscles of the trunk, arms and legs; usually occurs in older children and teens.
- Pleomorphic rhabdomyosarcoma – This type rarely occurs in children and instead typically occurs in adults age 30-50.
What are the symptoms of rhabdomyosarcoma?
The following are the most common symptoms of rhabdomyosarcoma. However, each child may experience symptoms differently. Many symptoms depend on the size and the location of the tumor. Symptoms may not be present until the tumor is very large, especially if it is located deep in the muscle or in the stomach. Symptoms may include:
- a tumor or mass that can be seen or felt (may or may not be painful)
- bleeding from the nose, vagina, rectum, or throat (may occur if the location of the tumor is in these areas)
- tingling, numbness, pain, and movement (may be affected if the tumor compresses nerves in the area)
- protrusion of the eye or a drooping eyelid (may indicate a tumor behind the area)
The symptoms of rhabdomyosarcoma may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.
How is rhabdomyosarcoma diagnosed?
In addition to a complete medical history and physical examination, diagnostic procedures for rhabdomyosarcoma may include:
- biopsy of the tumor - when a sample of tissue is removed from the tumor and examined under a microscope.
- blood and urine tests
- multiple imaging studies:
- computed tomography scan (Also called a CT or CAT scan.) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.
- magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.
- x-ray - a diagnostic test that uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.
- ultrasound (Also called sonography.) - a diagnostic imaging technique that uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels.
- bone scans - pictures or x-rays taken of the bone after a dye has been injected that is absorbed by bone tissue. These are used to detect tumors and bone abnormalities.
- bone marrow aspiration and/or biopsy - a procedure that involves taking a small amount of bone marrow fluid (aspiration) and/or solid bone marrow tissue (called a core biopsy), usually from the hip bones, to be examined for the number, size, and maturity of blood cells and/or abnormal cells.
- lumbar puncture/spinal tap - a special needle is placed into the lower back, into the spinal canal. This is the area around the spinal cord. The pressure in the spinal canal and brain can then be measured. A small amount of cerebral spinal fluid (CSF) can be removed and sent for testing to determine if there is an infection or other problems. CSF is the fluid that bathes your child's brain and spinal cord.
Diagnosis involves staging and classifying the tumor, which is important in determining treatment options.
Staging is the process of finding out whether cancer has spread, and, if so, how far. There are various staging systems that are used for rhabdomyosarcoma. Always consult your child's physician for more information on staging. One method of staging is the TNM staging system. This system uses tumor (T), nodes (N), and metastases (M) to differentiate the disease by stages. This system evaluates the disease before surgery and classifies it by one of the four following stages:
- stage I - tumors involving the area near the eye, the head, neck, and genitourinary tract (except the prostate and bladder). The tumor is localized, meaning the tumor has not spread to other areas of the body.
- stage II - small, localized tumors less than 5 cm in any site not in stage I. There are no tumor cells in the surrounding lymph nodes.
- stage III - localized tumor at any site not included in stage I that is smaller than 5 cm and has spread to surrounding lymph nodes or is larger than 5 cm and has not spread to surrounding lymph nodes.
- stage IV - disease that has spread to other areas of the body at the time of diagnosis.
Treatment for rhabdomyosarcoma:
Specific treatment for rhabdomyosarcoma will be determined by your child's physician based on:
- your child's age, overall health, and medical history
- extent of the disease
- your child's tolerance for specific medications, procedures, or therapies
- expectations for the course of the disease
- your opinion or preference
Three types of standard treatment are used to treat childhood rhabdomyosarcoma, most often in combination with each other:
This is the most common treatment for childhood rhabdomyosarcoma. Depending on where the cancer is, the surgeon will remove as much of the cancer as possible, along with some of the normal tissue around it. If the cancer is in a place where it cannot be removed, surgery may be limited to taking out only a small piece of the cancer. Surgery is usually followed by chemotherapy and radiation therapy.
Chemotherapy uses drugs to kill cancer cells. Chemotherapy may be taken by mouth in the form of a pill, or it may be put into the body by a needle in a vein or a muscle. Chemotherapy is called a systemic treatment because the drug enters the bloodstream, travels through the body, and can kill cancer cells throughout the body.
- Radiation therapy
Radiation therapy uses high-energy X-rays to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external radiation therapy) or from putting materials that produce radiation (radioisotopes) through thin plastic tubes in the area where the cancer cells are found (internal radiation therapy).
- Bone marrow transplantation
Bone marrow transplantation is a treatment being studied for recurrent childhood rhabdomyosarcoma. Sometimes rhabdomyosarcoma becomes resistant to treatment with standard doses of radiation therapy or chemotherapy. Very high doses of chemotherapy may then be ussed to treat the cancer. Because the high doses of chemotherapy can destroy the bone marrow, marrow is taken from the bones before treatment. The marrow is then frozen and high-dose chemotherapy with or without radiation therapy is given to treat the cancer. The marrow that was taken out is then thawed and given back through a needle in a vein to replace the marrow that was destroyed. This type of transplant is called an autologous transplant.
Treatment may also include (alone or in combination):
- lumbar puncture (to administer medication and treat cancer cells if found in this site)
- supportive care (for the side effects of treatment)
- antibiotics (to prevent/treat infections)
- bone marrow transplant
- continuous follow-up care (to manage disease and detect any recurrence of the tumor)
Long-term outlook for a child with rhabdomyosarcoma:
Prognosis greatly depends on:
- the extent of the disease.
- the size and location of the tumor.
- presence or absence of metastasis.
- the tumor's response to therapy.
- the age and overall health of your child.
- your child's tolerance of specific medications, procedures, or therapies.
- new developments in treatment.
As with any cancer, prognosis and long-term survival can vary greatly from child to child. Prompt medical attention and aggressive therapy are important for the best prognosis. Continuous follow-up care is essential if your child is diagnosed with rhabdomyosarcoma. Side effects of radiation and chemotherapy, as well as second malignancies, can occur in survivors of rhabdomyosarcoma.
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