Abstract
Ewing's sarcoma (ES) is the second most common bone tumor in children and adolescents. The prevalence is in the second decade, about 70% of patients are under 20 years of age.
EC is relatively rare in blacks and has a low incidence in Asia. No hereditary occurrence has been demonstrated.
The most commonly affected are the pelvis (25%), femur (16%), ribs (13%), tibia / fibula (9%) and humerus (6%). It is a systemic disease that spreads mainly through the hematogenous route.
About 25% of patients have detectable metastases at the time of diagnosis. The lungs (38%), skeleton (31%) and bone marrow (11%) are most often affected.
Liver and brain metastases are relatively rare (up to 5%). As a secondary radiation tumor, it is significantly less common than osteosarcoma (3% versus 69%).
Ewing's sarcoma mainly affects the skeleton, more rarely the soft tissues (extraskeletal form) and is most often of the undifferentiated type. The differentiated variant is known as peripheral primitive neuroectodermal tumor (PNET).
ES / PNET group tumors are characterized by chromosomal rearrangements that include the EWS gene on chromosome 22 (22q12) and the ets genes of the transcription factor group (FLI1, FEV, E1AE, ERG). The most common specific translocation is t (11,22) (q22, q12), which is present in more than 85% of patients.
Typical for ES are small round cells with less glycogen-rich cytoplasm and a round nucleus. Immunohistochemical examination reveals marked positivity of vimentin, evidence of neuronspecific enolase (NSE), S-100 protein and Leu-7, and strong CD99 expression.
The clinical picture of ES is dominated by pain and / or swelling at the site of involvement (61-96%), in about 20% they are the first sign of temperature. Back pain manifests itself in the vertebrae or paraspinal area, lameness and pain in the lower limb with possible neurological symptoms is usually when the pelvic bones are affected.
Metastases in the ribs or skull are usually seen as palpable resistance. Osteomyelitis, eosinophilic granuloma and large cell bone tumor should be ruled out in the differential diagnosis.
Malignant conditions include osteosarcoma, malignant fibrous histiocytoma or metastases of neuroblastoma. The definitive diagnosis is determined by histopathological examination from a biopsy sample.