Embrional rhabdomyosarcoma is the most common subtype of rhabdomyosarcoma, which affects children and adolescents.
Rhabdomyosarcoma is a soft tissue tumor,which most often occur in children and adolescents. Rarely, it is seen in adults over 40. Common sites where rhabdomyoma develops are head and neck (40%), genitourinary tract (20%), retroperitoneual cavity and the limbs. The tumor arises from mesenchymal cells (the precursors of skeletal muscles), that don’t differentiate normally.
There are several types of rhabdomyosarcoma distinguished – alveolar, embryonal, which comprises 60% of cases, and anaplastic rhabdomyosarcoma.
Annually occur 4.5 cases per million. The majority of the cases occur in children under 10 years, usually a person is at the age of 6-8 years when the diagnosis is made. The prevalence is a bit higher among males with a male to female ratio of 1.3:1.
Embryonal rhabdomyosarcoma accounts for approximately 60% of all rhabdomyosarcomas and affects children younger than 15 years.
Read also: Fibrosarcoma
Mutations in the RAS and FGFR4 genes, 11p15 are associated with embryonal rhabdomyosarcoma.
Both alveolar and embryonal subtypes are characterized by the over‐expression of insulin growth factor 2 (IGF‐2).
The tumor may be associated with other congenital disorders such as:
- neurofibromatosis type 1;
- Beckwith-Wiedemann syndrome;
- Li–Fraumeni syndrome;
- cardio-facio-cutaneous syndrome;
- Noonan syndrome;
- pleuropulmonary blastoma;
- Costello syndrome.
Possible link to parental use of cocaine and marijuana was reported.
The typical sites of the tumor are the orbit, the genitourinary tract and the retroperitoneum.
Common symptoms of rhabdomyosarcoma are the swelling/painful palpable mass at the site of origin along with other local symptoms – displacement of the eye, vaginal bleeding, dysuria, etc.
Rhabdomyosarcoma of the head and neck may be suspected when the following symptoms are present: diplopia (doubled vision), exophtalmos (bulging of the eyeball), headache, congestion, nasal discharge, cranial nerve palsy, obstruction, dysphagia, hearing or vision loss. Genitourinary rhabdomyosarcoma may cause urinary tract obstruction or constipation. Abdominal or pelvic manifestations include abdominal pain and abdominal mass, ascites, haematuria.
Embryonal rhabdomyosarcoma tends to disseminate widely, commonly to lungs, bones, bone marrow and brain.
The diagnosis is made based on:
- Radiographic imaging of the site of origin, chest X-ray;
- CT of the chest, tumor site;
- MRI of the tumor site;
- Total body bone scan;
- Biopsy of the lesion;
- Bone marrow biopsy;
- Lumbar puncture (only for parameningeal RMS)
The tumor consists of of round cells that remind embryonal cells. One subtype of embryonal myosarcoma known as the botryoid type usually locates in the visceral organs such as the vagina and the bladder. This neoplasm has a polypoid appearance and remind a “bunch of grapes”.
Treatment depends on the size of the tumor, its location and spread. Surgery solely is used when the tumor is localized. Some round cell tumours such as embryonal rhabdomyosarcoma, lymphoma or plasmacytoma require non‐surgical
protocols.The combination of surgery, chemotherapy, radiotherapy and immunotherapy is usually used.
Chemotherapy agents which are used in the treatment of rhabdomyosarcoma include vincristine, actinomycin D, doxorubicin, cyclophosphamide, ifosfamide, etoposide, melphalan and cisplatin.
Embryonal histology of the tumor usually indicates the better outcome. However, the older individual is the worse becomes the prognosis.
In general the survival rate is 70-75%. The five-year survival rate for low-risk is 95%, intermediate-risk – 65% and high risk – 15%.