Rhabdomyosarcoma overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Suveenkrishna Pothuru, M.B,B.S. [2]
Overview
Rhabdomyosarcoma is a malignant cancer, specifically a sarcoma (cancer of connective tissues), in which the cancer cells are thought to arise from skeletal muscle progenitors. Rhabdomyosarcomas can develop in any skeletal muscle in the body. Rhabdomyosarcoma is a relatively rare form of cancer. They are the most common type of soft tissue sarcoma in children. Embryonal rhabdomyosarcoma is the most common type of rhabdomyosarcoma. Development of rhabdomyosarcoma is result of specific genetic mutations. Its two most common forms are embryonal rhabdomyosarcoma and alveolar rhabdomyosarcoma. The microscopic pathology of rhabdomyosarcoma depends on the histological subtype. There are no established causes for rhabdomyosarcoma. The common sites of metastasis include lungs, bone marrow, and bone. Rhabdomyosarcoma is associated with a 5 year survival rate of 72%. Staging is based on "childrens oncology group" and is divided into four stages based on the location of tumor, size of tumor, involvement of lymph nodes, and metastasis. Symptoms of rhabdomyosarcoma include a rapidly growing mass and pressure effects on neurovascular structures. Treatment for rhabdomyosarcoma may consists of chemotherapy, radiation therapy and surgery.
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. The pathogenesis of alveolar rhabdomyosarcoma includes 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 the 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.
History and Symptoms
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 suggestive 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.
Other imaging findings
There are no PET scan findings associated with primary rhabdomyosarcoma lesions. PET scan may be considered for the diagnosis of metastatic lesions.
Other Diagnostic Studies
No additional tests are recommended for the diagnosis of rhabdomyosarcoma.
Treatment
Medical Therapy
Treatment for rhabdomyosarcoma may consists of chemotherapy, radiation therapy and surgery. Chemotherapy may be administered as neoadjuvant chemotherapy or adjuvant chemotherapy. Radiation therapy may be used as local therapy.
Surgery
Treatment for rhabdomyosarcoma may consists of chemotherapy, radiation therapy and surgery. Surgical resection of the rhabdomyosarcoma is often difficult or impossible because the tumor is usually embedded deep within the tissue, leaving it difficult to reach.