Classification of rhabdomyosarcomas and related sarcomas. Pathologic aspects and proposal for a new classification-an intergroup rhabdomyosarcoma study

Abstract

Background. There is a need to develop a single prognostically significant classification of rhabdomyosarcomas (RMS) and other related tumors of children, adolescents, and young adults which would be a current guide for their diagnosis, allow valid comparison of outcomes between protocols carried out anywhere in the world, and should enhance recognition of prognostic subsets. Method. Sixteen pathologists from eight pathology groups, representing six countries and several cooperative groups, classified by four histopathologic classification schemes 800 representative tumors of the 999 eligible cases treated on Intergroup Rhabdomyosarcoma Study II. Each tumor was classified according to each of the four systems by each of the pathologists. In addition, two independent subsamples of 200 of the 800 patients were reviewed according to the new system, so that 343 distinct patients were reviewed once, and 57 of these twice. Results. A study of the survival rates of all subtypes in the sample of 800 patients led to the formation of a new system. This was tested on two independent subsets of 200 of the original cases and found to be reproducible and predictive of outcome by univariate analysis. A multivariate analysis of the 343 patients classified according to the new system indicated that a survival model including pathologic classification and known prognostic factors of primary site, clinical group, and tumor size was significantly better at predicting survival than a model with only the known prognostic factors. Conclusion. This new classification, termed International Classification of Rhabdomyosarcoma (ICR) by the authors, was reproducible and predictive of outcome among patients with differing histologies treated uniformly on the Intergroup Rhabdomyosarcoma II protocols. We believe it should be utilized by all pathologists and cooperative groups to classify rhabdomyosarcomas in order to provide comparability among and within multi‐institutional studies. Cancer 1995;76:1073‐85.

Outcome of 449 adult patients with rhabdomyosarcoma: an observational ambispective nationwide study

“…Sharing the same classification would allow easier comparison between clinical presentation and behavior in adults and children. Finally, specific chemotherapy for A‐RMS and E‐RMS is an independent prognostic value in our study and others 2, 6, 7, 8, 9, 11, 14, 15, 38, 39, 40, 41, 43, 44, 45, 46, 47. North American and European pediatric groups have identified several risk factors (favorable location, IRSG stage, IRSG group, and age) to define the clinical group and deliver a regimen adapted to the risk group.…”

Rhabdomyosarcoma in adolescents: A CCHE experience

“…All diagnoses by our pathologists were classified according to the international classification [6] .…”

Higher rates of metastatic disease may explain the declining trend in Swedish paediatric rhabdomyosarcoma survival rates

“…It is a rare disease in adults, and the median age is 5 years of age 7, 10. Of the two main groups of histological classification, alveolar RMS and embryonal RMS, the latter is the more common and has a better prognosis 10, 11. The tumours can be located in all parts of the body where there is mesenchymal tissue, but the most frequent sites are in the head and neck region, in genitourinary sites and in limbs 3, 10, 12.…”