[Rhabdomyosarcoma and extraosseous Ewing's sarcoma]

Abstract

Rhabdomyosarcomas (RMS) and extraosseous Ewing's sarcomas (EOE) including malignant peripheral neuroectodermal tumors (MPNT) are the most frequent soft tissue malignancies of childhood. They account for 60.2% of 2.350 cases collected in the files of the Kiel Pediatric Tumor Registry. RMS: It is absolutely necessary to distinguish between embryonal (e) and alveolar (a) RMS, since these are two distinct tumor entities with significant differences in clinical presentation, morphology, molecular biology, cytogenetics and prognosis (Botryoid and spindle cell RMS are special variants of eRMS). The overall proportion of eRMS: aRMS is 2.4:1. Most cases of eRMS develop in the first 10 years of life (77.3%) while the age distribution of aRMS is almost constant in childhood and adolescence. Embryonal RMS exhibit a significantly higher proportion of male patients than aRMS (m:f = 1.72:1 vs. 1.06:1). A higher percentage of aRMS cases (25%) shows metastatic disease at the time of diagnosis than eRMS (8%), and the overall survival rates of aRMS are significantly lower even in localised disease (stage I-III) than in eRMS (59% vs. 76%; p < 0.002) (Data from the Cooperative Soft Tissue Sarcoma Study CWS). EOE: Despite proven histogenetic relationship (identical chromosomal rearrangements and fusion genes) the members of the Ewing's sarcoma (ES) family, classic ES and MPNT, whether osseous or extraosseous display significant differences in location, morphology and prognosis. Morphologically, MPNT and classic ES can be considered to be the extremes of a spectrum with overt neurodifferentiation in the former and lack of neural differentiation in the latter. Matched-pairs analysis of CWS EOE and MPNT cases show dramatically more unfavorable overall survival rates in MPNT than in EOE (45% vs. 67%).