Home What is Rhabdomyosarcoma?
What Is Rhabdomyosarcoma?
Sarcomas are cancers that develop from connective tissues in the body, such as muscles, fat, membranes that line the joints, or blood vessels. There are many types of sarcomas. Rhabdomyosarcoma is a cancer made up of cells that normally develop into skeletal muscles of the body. The body contains 3 main types of muscles.

* Skeletal (voluntary) muscles are muscles that we control to move parts
of our body.
* Cardiac muscle powers the heart's pumping action.
* Smooth muscle is present in internal organs. For example, smooth
muscle in the intestines pushes food along as it is digested. We do not
control this movement.

Skeletal muscles begin to form in embryos about 7 weeks into early embryonic development. At that time, rhabdomyoblasts (cells that will eventually form muscles) begin to form. It is these cells that can develop into the cancer called rhabdomyosarcoma. Because this is a cancer of embryonal cells, it is much more common in children, although it does occur in adults occasionally.
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Types of Rhabdomyosarcoma
There are 2 main types of rhabdomyosarcomas.

Embryonal rhabdomyosarcoma

Embryonal rhabdomyosarcoma (ERMS) is the most common type of rhabdomyosarcoma. It tends to occur in the head and neck area, bladder, vagina, and in or around the prostate and testes. ERMS usually affects infants and young children. The cells of ERMS look like the developing muscle cells of a 6- to 8-week-old fetus.

Two types of ERMS, botryoid and spindle cell rhabdomyosarcomas, tend to have a better prognosis (outlook) than the more common forms.

Alveolar rhabdomyosarcoma

Alveolar rhabdomyosarcoma (ARMS)occurs more often in large muscles of the trunk, arms, and legs and typically affects older children or teenagers. ARMS cells look like the normal muscle cells seen in a 10-week-old fetus.

Undifferentiated sarcoma

Some doctors group these uncommon cancers with the rhabdomyosarcomas. Although they are sarcomas, the cells don't have any features that help classify them further.
 
What Are The Key Statistics For Rhabdomyosarcoma?
About 3% of childhood cancers are rhabdomyosarcomas. About 350 new cases of rhabdomyosarcoma occur each year in the United States.

More than 9 out of 10 rhabdomyosarcomas are diagnosed in people younger than 25 years old. About 6 out of 10 of these cases are diagnosed in children under the age of 10. These tumors are usually embryonal rhabdomyosarcomas and occur in the head, neck, and genital and urinary tracts. Adolescents are more likely than younger children to have alveolar rhabdomyosarcomas, which are found more often in the arms, legs, or trunk.

The incidence (how common a disease is) has not changed much over the past few decades. This disease is slightly more common in boys than in girls. There is no particular geographic location or ethnic group that has an unusually high rate of rhabdomyosarcoma.

The prognosis (outlook for chances of survival) for rhabdomyosarcoma depends on many factors, including the location, type, and size of the tumor, the results of surgery, and whether the cancer has metastasized (spread). Children aged 1 to 9 tend to have a better outlook than infants or older children.
 
How Is Rhabdomyosarcoma Staged?
Staging is the process of finding out how far a cancer has spread. The outlook for chances of survival (prognosis) for people with cancer depends, to a large extent, on the cancer's stage. The stage of a cancer is one of the most important factors in choosing treatment.

Your child's doctors will use the results of the imaging tests the pathologist's biopsy reports, and the direct examination of the organs during surgery to determine how far the cancer has spread. If there is any doubt about the presence or absence of cancer, more biopsies may be done on tissue at the edge of the tumor, nearby lymph nodes, and any suspicious lumps in other parts of the body.

Staging for rhabdomyosarcoma is fairly complex. Doctors first determine 3 key pieces of information:

    * the type of rhabdomyosarcoma (embryonal vs. alveolar)
    * the clinical group
    * the TNM stage

These factors are then used to divide patients into risk groups, which in turn are used to determine the best treatment options.
 
Clinical groups
The clinical group is based on the extent of the disease and how completely it is removed during initial surgery. Briefly, the groups are defined as follows.

Group I

This group includes children with localized disease (the cancer has not spread to nearby lymph nodes or to distant sites in the body) and there is no evidence of any tumor left behind after surgery. Group I has 2 subgroups:

Group IA: Children in this group had a tumor that was still confined to the muscle or organ where it started and it was completely removed by surgery. It had not spread to nearby lymph nodes or distant sites.

Group IB: Children in this group had a tumor that had grown beyond the muscle or organ where it started and into nearby structures, but it was completely removed by surgery. It had not spread to nearby lymph nodes or distant sites.

About 15% of rhabdomyosarcoma patients are in group I.
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