Sarcomas are malignant tumors of mesenchymal origin.
The mesoderm differentiates into hematopoietic and connective tissue
Sarcomas arise from the skeleton and "supporting structures"
They can be defined in terms of the tissues they arise from and their location:
- Skeletal (voluntary muscle)
- Smooth (involuntary muscle)
- Connective tissue
- Adipose (fat)
- Vascular tissue
- Peripheral nervous system
There are many different types of sarcomas with different:
- Histological appearance
- Clinical behavior
Soft tissue Sarcomas (STS) :
Childhood muscle sarcomas are broadly grouped as:
- Rhabdomyosarcoma (RMS)
- Non-rhabdomyosarcoma soft tissue sarcoma (Non-RMS, NRMS or NRMSTS)
STS represent about 8% of all childhood malignancies.
The proportion of RMS and non-RMS are roughly equal.
Rhabdomyosarcomas (RMS) are thought to arise from immature mesenchymal cells that should normally be involved in the development of skeletal muscle. But, RMS can be found in areas where one would not expect to find striated muscle.
In Canada, between 2000 and 2004, rhabdomyosarcoma had a 5 year OSP (Observed Survival Proportions) for children between 0 and 14 years of 80%.
Non-Rhabdomyosarcoma tumors (non-RMS)
These are rare tumors and management of the different types overlaps
In the US, SEER have documented that roughly 4.5% of all childhood malignancies are Non-RMS.
The incidence of Non-RMS did not change between 1975 and 1999
In the US the overall 10 year survival in children with Non-RMS has not changed over the past 20 years and is roughly 73%. In the U.S there are 250 to 300 new cases per year of non-RMS.
Many different pathological types of tumors comprise non-RMS. Here are some examples:
- Liposarcomas (rare)
- Lipoblastoma (rare)
- Epithelioid sarcoma
- Synovial sarcoma
- Infantile fibrosarcoma
- Malignant fibrous histiocytoma
- Alveolar soft part sarcoma
- Clear cell sarcoma
- Peripheral nerve sheath tumor
- Dermatofibrosarcoma protruberans
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