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.
Although most of our skeletal muscles are in our limbs and
trunk, these cancers most often are found elsewhere in the body. Common
sites include:
- head and neck (near the eye, inside the nasal sinuses or
throat, or near the spine in the neck)
- urinary and reproductive organs (bladder, prostate gland,
or any of the female organs)
- arms and legs
- trunk (chest and abdomen)
But these cancers can occur anywhere in the body, including
sites that don't normally have skeletal muscle.
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.
Revised: 12/18/2007
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