Rhabdomyosarcoma overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
A rhabdomyosarcoma is a type of cancer, specifically a sarcoma (cancer of connective tissues), in which the cancer cells are thought to arise from skeletal muscle progenitors. It can also be found attached to muscle tissue, wrapped around intestines, or anywhere, to include the neck area. It is most common in children ages one to five, and teens aged 15 to 19, although quite rare in the latter. It can be a cardiac manifestation of tuberous sclerosis.
Rhabdomyosarcoma is a relatively rare form of cancer. Its two most common forms are embryonal rhabdomyosarcoma and alveolar rhabdomyosarcoma. In the former, which is more common in younger children, the cancer cells resemble those of a typical 6-to-8-week embryo. In the latter, which is more common in older children and teenagers, they resemble those of a typical 10-to-12-week embryo.
Classification
Rhabdomyosarcoma may be classified according to the "International classification of rhabdomyosarcoma" into six subtypes Alveolar rhabdomyosarcoma, embryonal rhabdomyosarcoma, botryoid rhabdomyosarcoma, spindle cell rhabdomyosarcoma, and undifferentiated rhabdomyosarcoma.
Pathophysiology
Rhabdomyosarcoma arises from the skeletal muscle cells. Development of rhabdomyosarcoma is result of specific genetic mutations. Genes involved in the pathogenesis of alveolar rhabdomyosarcoma include t(2;13) and t(1;13) chromosomal translocations. The microscopic pathology of rhabdomyosarcoma depends on the histological subtype.
Causes
There are no established causes for rhabdomyosarcoma.
Differential Diagnosis
Rhabdomyosarcoma of orbit must be differentiated from other causes of orbital masses such as orbital pseudotumor, orbital tumors, orbital abscess, and vascular lesions.
Epidemiology and Demographics
Rhabdomyosarcoma is a relatively rare form of cancer. It is most common soft tissue sarcoma in children. The overall incidence of rhabdomyosarcoma in children is approximately 0.45 cases per 100,000 children. Rhabdomyosarcoma tends to affect individuals <45 Years.
Risk Factors
The common risk factors in the development of rhabdomyosarcoma are Beckwith-Wiedemann syndrome, Li-Fraumeni syndrome, Costello syndrome, and Noonan syndrome.
Screening
Screening for rhabdomyosarcoma is not recommended.
Natural History, Complications and Prognosis
Common complication of rhabdomyosarcoma include metastasis to lung, bone marrow, and bone. Rhabdomyosarcoma is associated with a 5 year survival rate of 72%. The presence of metastasis is associated with a particularly poor prognosis. The embryonal type rhabdomyosarcoma is associated with the most favorable prognosis. Orbital and genitourinary tract rhabdomyosarcomas have the most favorable prognosis.
Diagnosis
Staging
According to the childrens oncology group, there are four stages of rhabdomyosarcoma based on the location of tumor, size of tumor, involvement of lymph nodes, and metastasis.
Physical Examination
Symptoms of rhabdomyosarcoma include a rapidly growing mass and pressure effects on neurovascular structures.
Laboratory Findings
An elevated concentration of skeletal muscle protein myo D1 is diagnostic of rhabdomyosarcoma.
CT
On CT scan rhabdomyosarcoma is characterized by soft tissue density, enhancement with contrast, and adjacent bone destruction.
MRI
On MRI rhabdomyosarcoma is characterized by low to intermediate intensity on T1, hyperintense on T2, and considerable contrast enhancement on T1 contrast.