Sarcomas are rare types of cancer that develop in the supporting tissues of the body, such as bone, muscle or cartilage.
There are two main types of sarcoma:
- Soft tissue sarcomas can develop in muscle, fat, blood vessels, or in any of the other tissues that support, surround and protect the organs of the body. More than half of all soft tissue sarcomas diagnosed in childhood are rhabdomyosarcoma. Other types of soft tissue sarcoma include fibrosarcoma, malignant peripheral nerve sheath tumours, peripheral primitive neuroectodermal tumours (pPNETs), Kaposi sarcoma and Ewing and Askin tumours of soft tissue.
- Bone sarcomas can develop in any of the bones of the skeleton. The two most common types of bone sarcoma in children are osteosarcoma and Ewing sarcoma.
RMS is the most common type of soft tissue sarcoma to occur in childhood.
It arises in muscle or fibrous tissue and can occur in almost any part of the body. The most common sites are around the head and neck, the bladder or the testes. Sometimes tumours may be found in a muscle or a limb, in the chest, or in the abdominal wall.
Occasionally, if the tumour is in the head or neck region, it can spread into the brain or the fluid around the spinal cord.
Nearly two thirds of RMS are of the embryonal sub-type (arising in primitive muscle cells). The other third are of the more aggressive alveolar sub-type.
The causes of RMS are unknown although children with certain rare genetic disorders, such as Li Fraumeni syndrome, have a higher risk of developing RMS.
RMS is the most common type of soft tissue sarcoma to occur in childhood, accounting for 53 per cent of cases (and four per cent of all childhood cancers). There are up to 60 new cases a year in the UK.
Incidence is greatest in children under the age of 10 years. The age distribution is different for boys and girls. In boys incidence peaks at age 3-4 years. In girls, it peaks earlier at 1-2 years and then declines. It is more common in boys.
Rhabdomyosarcoma Survival Rate
The five year survival rate for childhood RMS is 71%.
Age is an important prognostic factor. Children diagnosed at the age of 10-14 years have lower survival, around 50%, than children diagnosed at a younger age.
The overall survival rate for other types of soft tissue sarcoma is the same as RMS, at 71%, but the age pattern is different – with diagnosis during infancy being associated with a low survival rate.
Other important prognostic factors are the site, size, type of RMS, whether it has spread, associated genetic changes, whether complete removal is possible and general health of the child.
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