Embryonal rhabdomyosarcoma is the most common in young children but there has been report of a second age peak in adolescence years. United States
As the most common form of soft tissue sarcoma, RMS affects around 4.5 people per million individuals under the age of 20 in the United States. From 1975 to 2005 in the United States, there is a lower incidence rate of rhabdomyosarcoma and better 5-year survival rates in Native Indian/Alaskan Native/Asian/Pacific Islander children compared to white or black children; however, Native Indian/Alaskan Native/Asian/Pacific Islander make up only 6.5% of the total population studied. Global
The incidence of RMS in Europe is similar to that of the United States, while the incidence in some parts of Asia is half of the United States. Etiology
Embryonal rhabdomyosarcoma results from copy number alterations as well as mutations in the RAS pathway. Genomic patterns associated with ERMS include the gains in chromosomes 8, 2, 11, 12, 13, and/or 20 and losses in chromosomes 10 and 15. Another common genomic alteration is loss of heterozygosity at chromosome 11p, the short arm of chromosome 11. It is believed that some of the identifying genetic mutations that can cause ERMS include p53 loss, RAS pathway activation, MYOD1 mutations. Patients in the fusion-negative group had different genetic mutation profiles than those in the fusion-positive group.Focusing on the fusion negative population, it was shown that the most fusion-negative tumors were caused by RAS isoform mutations.
In either case, "fusion-negative" alveolar rhabdomyosarcoma have similar clinical presentation and outcome as embryonal rhabdomyosarcoma, thus risk stratification, prognosis, and treatment intensity of rhabdomyosarcoma are now determined by fusion-status instead of histological classification. Imaging
After a physical exam, formal diagnosis of RMS in adult patients requires a computed tomography (CT) scan, which can assess the areas affected and to delineate the tumor. In children, physicians may opt for magnetic resonance imaging (MRI) to limit radiation exposure in younger populations. In the majority of individuals diagnosed with rhabdomyosarcoma, more than half are diagnosed before the age of 10. Prognosis
The prognosis for rhabdomyosarcoma has improved greatly in recent decades, with over 70% of people surviving for five years after diagnosis. The combined use of radiotherapy and surgery has significantly reduced the mortality rates compared to patients who did not undergo any radiotherpay or chemotherapy treatments. Embryonal rhabdomyosarcoma is generally associated with better prognosis than alveolar rhabdomyosarcoma, with a 5-year survival prognosis of 82% and 53%, respectively. This may be due to the more aggressive and metastatic nature of ARMS that can be attributed to its PAX3–FOXO1 or PAX7–FOXO1 gene fusions. Nevertheless, some embryonal rhabdomyosarcoma patients with a rare Leu122Arg mutation in MYOD1 gene have a very poor outcome. In two different studies, none of the subjects with the MYOD1 mutation survived. Tumors due to this mutation commonly manifest in the head and neck area, causing the mutated protein to behave like an oncogene.There have not been many studies linking the genetic profile and clinical outcome of ERMS.